THE ANALYSES TO DETERMINE THE RELATIONSHIP BETWEEN SLEEPING PROBLEMS AND THE HEALTH OUTCOMES OF THE ELDER PEOPLE

Transcription

1 THE ANALYSES TO DETERMINE THE RELATIONSHIP BETWEEN SLEEPING PROBLEMS AND THE HEALTH OUTCOMES OF THE ELDER PEOPLE A study submitted in partial fulfillment of the requirements for the degree of Master of Science in Information Systems Management at THE UNIVERSITY OF SHEFFIELD by HANYAN LI September 2012

2 Abstract Background. The previous literature indicates that sleeping problems is a common problem in general public especially among the older people. Sleeping problems could be one factor that affect people s physical and psychological health. Aims. This study aimed to investigate the relationship between sleeping problems and physical health, psychological health and mortality among the older people. Methods. In this study, different types of test like chi-squared test and logistic regression analysis have been used to analyse the data of The Nottingham Longitudinal Study of Activity and Ageing in order to investigate the relationship between sleeping problems and the health outcomes among the older adults. Results. According to the results of various types of analyses, age and gender are two variables that are related to sleeping problems significantly. Self-rated health and 13-item health index which are two variables represent physical health were found to be associated with sleeping problems. All the variables about physical activity are not associated with sleeping problems significantly after other variables have been controlled except bend score has been found associated with sleeping problems among the female respondents. Psychological health is related to sleeping problems among the overall respondents and among the female respondents but is not related among the male respondents. The results of Cox regression indicate that sleeping problems are not associated with mortality. Conclusions. Sleeping problems are associated with physical health significantly among the overall respondents and among the males and females separately. For the overall respondents, psychological health that whether the respondents were depressed is associated with sleeping problems, but among the males psychological health is not 1

3 related to sleeping problems significantly. For the females, bend score, physical and psychological health are all associated with sleeping problems. However, sleeping problems are not predictor of mortality among the overall respondents or among the males and females. 2

4 Acknowledgements I want to thank Dr Peter Bath for being so kind and patient to give me all the helpful advices and guidance. The support was so important for me and I really appreciated that. I also want to thank my classmates who have discussed the dissertation and the use of software with me. 3

5 Contents 1 Introduction Background Aim and objectives Scope Structure overview Conclusion Literature review Introduction Overview of sleeping problems Overview of prevalence of sleeping problems Overview of the sleeping problems among the elder adults Overview of the relationship between sleeping problems and health outcomes among the older people Overview of the association between sleep disorder and mortality among the elder people Overview of the Nottingham Longitudinal Study of Activity and Ageing Conclusion Methodology Introduction Research methods The methodology of the Nottingham Longitudinal Study of Activity and Ageing (NLSAA) Sample Survey assessment Sleeping problems Social engagement

6 3.3.5 Psychological health Physical health Customary physical activity Statistical analysis Descriptive Statistics Bivariate analysis Conclusion Initial results Introduction Descriptive statistics Age distribution Sex distribution Social class Sleeping problems Problems of falling asleep Sleep onset latency Problems of staying asleep Problems of waking up too early The prevalence and severity of sleeping problems Sleeping problems of respondents in the interview week the users of drugs to aid sleep Anxiety and depression status Self-rated health Thirteen-item health index Social engagement status Outdoor physical activity

7 Indoor productive activity Leisure activity Total effort score Total bend score Chi-squared test Age and sleeping problems Gender and sleeping problems Social class and sleeping problems Problems of falling asleep and staying asleep Problems of falling asleep and waking too early Problems of staying asleep and waking too early Sleeping problems and self-rated health Sleeping problems and physical health index Sleeping problems and psychological health Sleeping problems and social engagement Sleeping problems and outdoor activity Sleeping problems and indoor activity Sleeping problems and leisure activity Sleeping problems and total effort score Sleeping problems and total bend score Logistic regression analyses Cox regression analyses Conclusion Discussion Introduction Descriptive statistics

8 5.3 Factors associated with sleeping problems Sleeping problems and mortality Conclusion Conclusions and recommendations...98 Bibliography

9 Figures and tables Table 4.1 Age distribution in NLSAA in Table 4.2 sex distribution in NLSAA in Figure 4.1 sex distribution in NLSAA in 1985 (Pie chart) Table 4.3 social class distribution in NLSAA in Figure 4.2 social class distribution in NLSAA in 1985 (Bar chart)...34 Table 4.4 sleeping problems in NLSAA in Figure 4.3 sleeping problems in NLSAA in 1985 (Bar chart) Table 4.5 problems of falling asleep in NLSAA in Figure 4.4 problems of falling asleep in NLSAA in 1985 (Bar chart) Table 4.6 sleep onset latency in NLSAA in Table 4.7 problems of staying asleep in NLSAA in Figure 4.5 problems of staying asleep in NLSAA in 1985 (Bar chart)...39 Table 4.8 waking too early in NLSAA in Figure 4.6 waking too early in NLSAA in 1985 (Bar chart) Table 4.9 severity of sleeping problems in NLSAA in Figure 4.7 severity of sleeping problems in NLSAA in 1985 (Bar chart) Table 4.10 sleeping problems in interview week in NLSAA in Table 4.11 users of drugs to aid sleep in NLSAA in Table 4.12 anxiety and depression status in NLSAA in Table 4.13 depression scores in NLSAA in Table 4.14 the distribution of depressed respondents in NLSAA in Figure 4.8 the distribution of depressed respondents in NLSAA in 1985 (Bar chart)..47 Table 4.15 self-rated health in NLSAA in

10 Figure 4.9 self-rated health in NLSAA in 1985 (Bar chart) Table item health index in NLSAA in Table 4.17 social engagement score in NLSAA in Table 4.18 social engagement level in NLSAA in Table 4.19 outdoor physical activity in NLSAA in Table 4.20 indoor productive activity in NLSAA in Table 4.21 leisure activity in NLSAA in Table 4.22 total effort score in NLSAA in Table 4.23 total bend score in NLSAA in Table 4.24 Frequency table for sleeping problems according to age group Table 4.25 Frequency table for sleeping problems according to gender Table 4.26 Frequency table for sleeping problems according to social class...58 Table 4.27 Frequency table for problems of staying asleep according to problems of falling asleep Table 4.28 Frequency table for problems of waking up too early according to problems of falling asleep Table 4.29 Frequency table for problems of waking up too early according to problems of staying asleep...61 Table 4.30 Frequency table for sleeping problems according to self-rated health...62 Table 4.31 relationship between sleeping problems and health index...63 Table 4.32 Frequency table for sleeping problems according to psychological health63 Table 4.33 Frequency table for sleeping problems according to social engagement. 64 Table 4.34 Frequency table for sleeping problems according to outdoor activity...64 Table 4.35 Frequency table for sleeping problems according to indoor activity Table 4.36 Frequency table for sleeping problems according to leisure activity

11 Table 4.37 Frequency table for sleeping problems according to total effort score Table 4.38 Frequency table for sleeping problems according to total bend score Table 4.39 shows the results of logistic regression analysis carried out to determine the relationship between sleeping problems and various independent variables...69 Table 4.40 shows the relationships between sleeping problems and independent variables among males...74 Table 4.41 shows the relationships between sleeping problems and independent variables among females Table years all-cause mortality according to sleeping problems...87 Table years all-cause mortality according to sleeping problems among males 89 Table years all-cause mortality according to sleeping problems among females

12 1 Introduction 1.1 Background Sleeping problems are very common in general public (Ancoli-Israel and Cooke, 2005). Population based researches indicate that approximately 30% of the adults are affected by sleeping disorder in various degree and 10% even admit they have chronic insomnia (Fullerton, 2006). Insomnia is the most popular sleeping problems which presents including difficulty of falling asleep, staying asleep and waking too early (Stone et al., 2008). Insomnia is the complaints about insufficient sleep which is subjective and insomnia could affect daytime functioning (Fetveit et al., 2008). Age may be one important factor that affects the risk of sleeping problems (Ancoli-Israel and Cooke, 2005). Sleep disorder is a common problem among the elder people. The prevalence of insomnia among the older adults is very high (Reeder et al., 2007). In one study which include 9,000 respondents aged 65 and over, approximately 12% of the participants reported no sleeping problems and over half of the respondents admitted that they had chronic sleeping problems (Ancoli-Israel and Cooke, 2005). It has been reported that about 20% of the Japanese and about 33% of the older Japanese had sleeping problems (Tanaka and Shirakawa, 2004). Sleeping problems are now becoming one severe social problem in Japan (Tanaka and Shirakawa, 2004). There are increasing evidence indicates that sleep quality could affect health including both physical and psychological health (Tanaka and Shirakawa, 2004). Some study find that the elder people who are suffering the sleep disturbance are often associated with some chronic disease or other physical and mental health conditions (Foley et al., 2004).The identification of sleeping problems could lead to better management of illness and life quality among the elder adults (Reid et al., 2006). The prevalence of age-related insomnia seems continue to increase and the need exists for an epidemiological overview about this issue (Morgan et. al, 1988). Besides, previous studies were seldom looking into the incidence and outcomes associated with sleep disorder among the elderly (Morgan and Clarke, 1997). This study will seek to investigate if there is any 11

13 association between sleeping problems and the health outcomes of the elderly and if there is a relationship between insomnia and mortality among older people by analysing the data of Nottingham Longitudinal Study of Activity and Ageing. This study focus on analysing the Nottingham Longitudinal Study of Activity and Ageing data to examine if there is an association between sleep disorder and health outcomes among the older people. The survey of NLSAA was carried out in three areas in Nottingham which at the time gave a good representation of the elder people being studied (Morgan, 1998). The Nottingham Longitudinal Study of Activity and Ageing (NLSAA) was carried out in 1985 and aimed to investigate the longitudinally and cross-sectional association between physiologically relevant levels of physical activity and other aspects about health including psychological status etc among the older adults (Morgan, 1998). There are many previous studies use the Nottingham Longitudinal Study of Activity and Ageing data to investigate several aspects of activity and wellbeing of the elder people, like the difference of self-rated health between females and males (Bath, 2003) and customary physical activity (Bath & Morgan, 1998). However, the issues related to the sleeping problems among the elderly have been seldom researched (Morgan et al., 1988; Morgan et al., 1989). Based on the results of the Nottingham Longitudinal Study of Activity and Ageing data, there are several types of sleep disorder. One is that the respondents find it is difficult to fall asleep and other one is that the respondents have trouble staying asleep and the last type is that the respondents always waking too early in the morning. In this study, the three types of sleep disorder will be analysed and discussed as sleeping problems rather than separately since these are all sleep disorder but different symptoms of sleeping problems. 12

14 1.2 Aim and objectives The aim of this dissertation is to investigate the relationship between sleeping problems and the health outcomes among the elder people. The data of the Nottingham Longitudinal Study of Activity and Ageing (NLSAA) will be analysed to conduct this study. To be specific, the objectives are as follows: To review the previous researches on sleeping problems among the older people, the association between sleep disorder and the health of the elderly and other related research on the data of NLSAA. To identify the factors which are associated with the sleep disorder, like age, gender, social class etc. To investigate whether there is any relationship between insomnia and health conditions of the respondents including physical and psychological health. To investigate whether there is any longitudinal relationship between insomnia and mortality among elderly people. 1.3 Scope Section 9 of the Nottingham Longitudinal Study of Activity and Ageing data catalogue which is about the sleep and sleeping problems of the respondents will be used to carry out the research. Other Data will also be used including the physical activity scores, 14 item physical health score and depression scores which address the psychological health of the participants etc. Many researches have been done previously using the data of Nottingham Longitudinal Study of Activity and Ageing, but the issues about sleeping problems have been neglected. This study will focus on investigating the issues of sleeping problems among the elder adults analysing the NLSAA data. 13

15 1.4 Structure overview This study includes the following chapter headings: Chapter 2 is the literature review which presents the previous researches related to the topic of this study. An introduction of sleeping problems, the prevalence of sleeping problems among the older people and other research questions related to sleeping problems including the relationship between sleeping problems and health in previous studies and researches. The previous studies done by analysing the NLSAA data have also been included. Chapter 3 is the methodology which describes and introduces the methods and methodology which have been used in this study. The methodology of NLSAA survey has been described which include introduction of the sample and how the data was collected etc. The details of variables which will be used to analyse have all been given and the methods of analysing the data have also been presented in details. The tools and statistical test which will be adopted to analyse data like chi-squared test, logistic regression and Cox regression are discussed in this chapter and the models built for the tests are also described. Chapter 4 presents the initial results of the data analyses and in chapter 5 the results of the various analyses will be discussed. In chapter 5, findings of this study will be presented and discussed. Chapter 6 conclusion reviews the aim and objectives of the study and then discusses and presents the findings which summarise the findings of this study. 1.5 Conclusion In this chapter, background about the sleeping problems among the older people and the need for further research about sleeping problems and health outcomes among the elder adults have been given. The aim and objectives of this study and a structure overview 14

16 have also been presented. In the next chapter, the literature about sleeping problems, the prevalence of sleeping problems among the older people and the relationship of sleeping problems and health will be reviewed in details. 2 Literature review 2.1 Introduction The previous chapter describes the aim and objectives of this study and conduct an introduction of the background and importance in this area. In this chapter, the previous literature about sleeping problems in many aspects will be discussed and an overview of related aspects of sleeping problems will be given. The overview of the Nottingham Longitudinal Study of Activity and Ageing (NLSAA) will be conducted at the last part of this chapter. 2.2 Overview of sleeping problems This study is carried out using the data of Nottingham Longitudinal Study of Activity and Ageing. There are several types of sleeping problems like sleep fragmentation, insomnia and daytime sleepiness. (Paudel et al., 2008). Sleeping problems may become a serious public problem since people could be affected in terms of their life quality and well being (Hayashino et al., 2010). What is more, sleeping problems could be very costly. For instance, the direct economic loss of insomnia in America was proximately $30 billion in 1995 (Hayashino et al., 2010). According to the survey interview and data catalogue of NLSAA, the sleeping problems discussed in this article are mainly complaints of insomnia. The definition of insomnia has changed several times over the last few years to indicate the alteration of how people understand it. At first, insomnia means unsatisfactory sleep promoted by the American Institute of Medicine in 1979, then the concept means that the almost nightly complaints of the feeling of tried or insufficient sleep even after a long period of sleep in 1990 by the International Classification of Sleep Disorders and this concept has been standardised utilised in 15

17 several epidemiological studies (Ohayon, 2002). Same as in the survey interview and data catalogue of NLSAA, majority of studies focused on the three different types of insomnia symptoms: difficulty in falling asleep, trouble with staying asleep and waking too early in the morning (Ohayon, 2002). 2.3 Overview of prevalence of sleeping problems In previous studies, sleeping problems have been found to be a major concern for many individuals. In the study of Almeida et al., 3029 respondents complained their poor sleep which count for 60% of the total respondents. Among those respondents who have sleeping problems, 384 respondents was suffering from staying awake for the entire night, 692 of them had trouble of falling asleep and 2864 respondents woke too early in the morning (Almeida et al., 2011). From 5% to 10% of the adults have sleeping problems and insomnia is a common situation that is treated in general practice (Morgan and Clarke, 1997). In other study, the results are about one-third of the individuals complained about sleeping problems (Ancoli-Israel and Cooke, 2005). In general population, approximately 36% of people have reported their complaints about sleeping problems and 50% of the elder people have complained about sleeping problems (Paudel et al., 2008). What is more, three-fourth of these individuals who are complaining about their sleep disorders claims their situation as occasional. At average, they suffer 6 nights of insomnia per month. However, the other quarter admit that their situation is severe that they suffer choric insomnia. They may have trouble of sleeping for 16 nights per month on average (Ancoli-Israel and Cooke, 2005). According to the previous studies, insomnia is more prevalent among the elder people and women (Ohayon, 2002). Gender could be one factor that affects the quality of sleep according to many studies (Qiu et al., 2011). Women tend to complain about the insomnia symptoms more than men do (Ohayon, 2002; Leger et al., 2000; Olson, 1996). However, there are many other economical and sociological factors may have affected the prevalence of sleep disorder (Ohayon, 2002). 16

18 2.4 Overview of the sleeping problems among the elder adults The prevalence of sleeping problems among the older people is really high. In a study of more than 9,000 participants aged 65 and over, only 12% of they reported no sleep complaints (Ancoli-Israel and Cooke, 2005). In other study, 68.9% of participants admitted at least one sleeping problem and 40% of the respondents had two or more (Reid et.al, 2006). Respondents most commonly reported that they had trouble of falling asleep, staying asleep or wake up too early (Reid et.al, 2006). It is widely accepted that the older people are the most vulnerable group of individuals to the sleep disorder (Morgan and Clarke, 1997). Nearly 50% of people older than 65 years reported problems of falling or remaining asleep (Foley et al., 1995). On one hand, some results of previous study indicate that many elder people with sleep disorder already had these problems when they were young instead of developing the problem in later life (Morgan et al., 1989). On the other hand, other factors also contribute to the sleep disorder among the elderly like increasing levels of illness and normal health conditions change relating to growing old (Morgan et al., 1989). It is not certain that the complaints of sleep disorder are the natural situation of growing older or maybe it is evidence of some current or future health problems (Almeida, 2011). In the previous studies, the outcomes which are associated with sleeping problems among the elder adults have been seldom researched (Morgan & Clarke, 1997). In the study of Morgan and Clarke, the data of NLSAA also has been utilised and analysed. From the data of NLSAA in 1985, 1023 participants were available for the sleep quality information. Among them 221 participants met the criteria of insomnia and the overall prevalence was 21.2% (Morgan & Clarke, 1997). Those participants with insomnia reported longer sleep latencies and shorter sleep times (Morgan & Clarke, 1997). Gender may be one significant factor that affects the distribution of sleeping problems among the elder people (Qiu et al., 2011). Majority of previous studies agreed that there is a stronger association between sleeping problems and health outcomes in women than in men (Qiu et al., 2011). Previous study using data of NLSAA had found that there is 17

19 an association between subjective sleep quality and gender, and a relationship between sleeping problems and marital status (Morgan et.al, 1988). Women who were not married tended to have sleeping problems. However, the results of analysing the data of NLSAA showed that there is no significant association between sleep disorder and age (Morgan et.al, 1988). After calculating the sleep onset latency and total time in bed, it indicated that those respondents who claimed themselves having insomnia severely are associated with longer sleep onset latency and total time in bed (Morgan et.al, 1988). In terms of persistence, previous study found that the patients symptoms of insomnia continue during their later life (Morgan and Clarke, 1997). The elder adults who have trouble of sleep disorder in their early age seem more likely to have the chronic symptom (Morgan and Clarke, 1997). The importance of responses to sleep complaints among the older people has already been realised and the attention is focusing on counselling and psychological therapies etc (Morgan et. al, 1989). 2.5 Overview of the relationship between sleeping problems and health outcomes among the older people Sleeping problems are a major concern for the elder individuals, not only because it is very common, but also since it could cause much relevant daytime impairment (Ancoli-Israel and Cooke, 2005). The prevalence of sleep disorder seems to be higher among the elder adults who are in poor health (Ancoli-Israel and Cooke, 2005). Insomnia could affect individuals life in many ways, like daytime function because people need more time to nap, cognitive ability especially attention and memory, slowing response time (Ancoli-Israel and Cooke, 2005). There are increasing evidence shows the association between sleep disorder and health outcomes. According to the previous studies, good quality of sleep could contribute to reducing the risk of mortality and improving health in later life (Qiu et al., 2011). On the other hand, insufficient sleep could be a significant factor for poor physical and psychological health (Qiu et al., 2011). The study of Morgan et al. in 1988 indicated that the interviewers who have been classified as having sleeping problems were more likely to have higher anxiety index and to rate their health below the average standard (Morgan et. al, 1988). In previous study about analysing the data of Nottingham Longitudinal Study of Activity and 18

20 Ageing, the quality of sleep was considered to be a significant index for physical and psychological health. The respondents who considered they had sleep disorder sometimes were more likely to visit their doctors in the month before the interviews and to admit that they have symptoms of anxiety or depression (Morgan et. al, 1988). However, the causality of relationship between sleep problems and health is still not clear (Qiu et al., 2011). On one hand, poor health could cause poor sleep quality and sleep disorder (Qiu et al., 2011). According to the study of Reid et al in 2006, the complaints of sleeping problems were associated with mental and physical health conditions among the older people. The older individuals who have chronic disease, poor self-rated health and mental disease tend to report more about sleeping problems (Bazargan, 1997; Chiu, 1999). Previous studies indicate that sleep disorder among the older peopel is associated with a higher incidence of poor health status and all-cause mortality (Paudel et al., 2008). There are studies suggested an association between sleep disorder and the incidence of comorbid conditions, like diabetes, hypertension, stroke, heart disease and cancer (Hayashino et al., 2010). According to the results, sleep disorder increased linearly with the number of comorbid conditions increased and this suggested that the incidence of comorbid conditions could worsen sleep disorder (Hayashino et al., 2010). On the other hand, sleeping problems may contribute to poor health (Qiu et al., 2011). It has been found that better sleep quality could help the older people improve their health (Tanaka & Shirakawa, 2004). In the research of Qiu et al, they examined the relationship between self-reported sleep quality and the health outcomes among the older people in China. Their results of Logistic regressions indicated that poor sleep was associated with worse health condition three years later (Qiu et al, 2011). Some researches have investigated if sleeping problems are associated with depression. Though there were many studies which have suggested a relationship between depression and sleep disorder, they have been limited by small sample sizes and 19

21 sampling methods (Paudel et al., 2008). In the study of Cho et al. in 2008, 351 elder people participated in the 2-year follow up study and 145 were patients of depression. Sleep disorder at the baseline has an association with greater hazard of depression in the following year (Cho et al., 2008). Sleeping problems could increase the occurrence of depression over time (Almeida et al., 2011; Kim et al., 2009). There is one longitudinal study which was with an average follow-up period of 6 years (Almeida et al, 2011). In this study, there was 5127 community-dwelling Western Australian older men took part in. The study found that 60% of the respondents claimed that they have at least one sleep problem. The men reported at least one sleep problem and that the unadjusted hazard ratio of depression was higher among the respondents who reported difficulties to fall asleep (HR=2.19, 95% confidence interval 95% CI= ) or to stay asleep (HR=1.94, 95% CI= ) (Almeida et al, 2011). It seems that there was no relationship between early morning awakening and incident depression. After the analyses were adjusted for other measured factors, the relationship between trouble of falling asleep and incident depression remained (HR=1.94, 95% CI= ). However, the relationship between difficult of staying asleep and incident depression was not significant any more (HR=1.43, 95% CI= ) (Almeida et al, 2011). The results of Almeida et al suggested that the relationship between sleeping problems and depression cannot be explained properly as reverse causality (Almeida et al, 2011). Sleep disorder could also affect people s well-being relating to anxiety which is suggested by the association between sleep disorder and health status among the elder adults (Morgan et al., 1989). 2.6 Overview of the association between sleep disorder and mortality among the elder people Many previous researches have been conducted to investigate if sleep disorder affect the mortality of patients. For example, Kripke et al did their study in 2002 about the association between mortality and insomnia. There were 1.1 million respondents but not 20

22 only the older people. They found that the respondents who slept 7 hours per night were the best survival. Respondents who sleep less or more tend to have a higher hazard of mortality. However, the results showed that there were not any association of insomnia and excess mortality. (Kripke et al, 2002). Men who reported the complaints of sleep disorder had higher mortality hazard than others, even though such association was not significant after other factors like demographic and prevalent disease taken into consideration (Almeida et al., 2011). It is agreed that sleep disorder is associated with shorter survival. The all cause mortality among the elder people who have sleeping problems is up to two times higher than others without the problem (Ancoli-Israel & Cooke, 2005). The study of Qiu et. al in 2011 found that participants who admitted sleeping problems and participant who have fair sleep quality had a 26% (HR = 1.26, 95% CI: ) and 10% (HR = 1.10, 95% CI: ) higher mortality risk than respondents who admitted good sleep respectively after the age, ethnicity, location been controlled (Qiu et.al, 2011). Among the oldest-old group of the study, the association between sleeping problems and mortality was the strongest (Qiu et.al, 2011). Besides, the baseline health is very significant because it affects the association between sleep and mortality in short term and the baseline health status could be one important predictor of mortality and subsequent health status (Qiu et.al, 2011). On the other hand, some research found that insomnia and mortality was not significantly associated. According to the research conducted by Mallon et al in 2000, the results were sleeping problems in women can predict subsequent depression but there was no association between sleep disorder and mortality. Among the older men, sleeping problems predicted mortality (OR = 1.7; 95% CI ) but after adjustment for an array of possible risk factors, the relationship is not significant any more (Mallon et al., 2000). 21

23 2.7 Overview of the Nottingham Longitudinal Study of Activity and Ageing The Nottingham Longitudinal Study of Activity and Ageing is a longitudinal survey initiated in May 1985 which contains information of many aspects of people aged 65 and over (Bath and Morgan, 1998). The NLSAA study design has been considered to be both powerful and productive (Morgan, 1998). The study contains 17 catalogues exclude introduction and appendices, many aspects of physical activity and health conditions of the older people are included (Bath and Morgan, 1998). Such as, catalogue of chest pains and dyspnoea, and catalogue of sleep, sleeping problems, use of hypnotics and other medication etc. The study covered three different areas in Nottingham which were Meadows, Beeston and Clifton. In 1985, the baseline survey was carried out and there were 1042 people had been interviewed. Those individuals are sampled randomly of which the response rate was 80%. There were interviews during May and September 1985 by trained people. Subjective sleep problems, psychological health status which was evaluated using the Symptoms of Anxiety and Depression (SAD) scale were all included in the data. Two follow-up surveys had been conducted in 1989 and 1993 respectively. All interviewers who were interviewed originally and still in Nottingham were all received invitation to participate in the follow-up study. The follow-up response rate was 88% in 1989 and 78% in 1993 (Morgan and Bath, 1998). In NLSAA, the information about sleeping habits, subjective sleep status and physical and psychological health were received from the 1023 participants who were all randomly chosen (Morgan, 1998). According to the study of Morgan in 1988, sleep quality is one significant index of psychological and physical health status. According to the data, the subjective insomnia was reported by 37.9% of the participants (Morgan, 1998). In the study of Morgan in 1998, the results indicates that symptoms of anxiety, gender and self-rating health were the important factors which are predictors of sleeping problems (Morgan, 1998). Therefore, the participants who reported sleeping problems were more likely to be women, had high anxiety scores and rated the health as poor. The 22

24 results suggested that insomnia in later life could be affected by psychological problems and physical health problems (Morgan, 1998). 2.8 Conclusion In this chapter, the definition of sleeping problems and previous literature research about the prevalence of sleeping problems, sleeping problems among the elder individuals, sleeping problems and the health outcomes and the association between sleep disorder and mortality have all been carried out. In the next chapter, the methodology utilised in this study to analyse the data of NLSAA will be discussed and the steps about analysing the data will also be given. 3 Methodology 3.1 Introduction The previous chapter reviews the studies and researches about sleeping problems and the relationship between sleeping problems and health outcomes which have been done by others. This chapter introduces the methodologies and methods used in this study. The methodology of the Nottingham Longitudinal Study of Activity and Ageing (NLSAA) is also been presented. 3.2 Research methods The research method utilised in this study is survey research. Survey research usually needs to collect and analyse information by questioning particular individuals who are the entire research population or a sample which could represent the population (Pickard, 2007). Survey research could be used to investigate the relationship between particular variables which is appropriate for this study (Pickard, 2007). 23

25 In terms of data collection, the data needed in this study is data of the Nottingham Longitudinal Study of Activity and Ageing (NLSAA). The Nottingham Longitudinal Study of Activity and Ageing (NLSAA) is a questionnaire based study. Survey information is commonly collected by a questionnaire which includes pre-determined structured questions and those questions could be answered by mail or asked by interviewers (Burns, 2000). Questionnaires are the most popular data collection techniques in researches referring to human subjects (Pickard, 2007). 3.3 The methodology of the Nottingham Longitudinal Study of Activity and Ageing (NLSAA) The Nottingham Longitudinal Study of Activity and Ageing (NLSAA) aims to study the cross-sectional and longitudinal associations between levels of customary physical activity in terms of physiological aspects and functional ability, physical health and mental health status of the older people (Morgan, 1998) Sample The data were obtained in three waves: baseline in 1985, a first follow-up in 1989 and a second follow-up in 1993 in a panel study structure (Morgan, 1998). The sample included individuals who lived in three areas of Nottingham to ensure the demographic composition of the sample represented the national pattern of England and Wales (Morgan and Clarke, 1997). Among all the eligible people who aged over 65, 1299 were randomly selected for interview and 1042 agreed to be interviewed giving a response rate of 80% (Morgan, 1998). The follow-up surveys were conducted in 1989 and 1993 and all the participants who were surviving and still living locally were invited to participate in follow-up interviews (Morgan and Clarke, 1997). In 1989, 690 respondents participated in the interview again and the re-interview rate was 88%. For the second follow-up, there were 410 individuals among the survivors agreed to be re-interviewed with the rate of 73% (Morgan, 1998). 24

26 3.3.2 Survey assessment Many aspects of health status, lifestyle and wellbeing among the elder people have been covered in the structured questionnaire which contained 318 items (Morgan, 1998). The items which analysed in this study or related to the subject are discussed below Sleeping problems In NLSAA, many aspects related to sleeping problems have been investigated like sleep onset latency, subjective insomnia and usage of hypnotics. For data related to sleeping problems, the first section is mainly about the time respondents spent in bed, the time they spent asleep and the time respondents taken to fall asleep. The data in the first section is the objective aspects of sleeping problems. Second section is the self-reported sleeping problems. Respondents first talked about their general feelings about whether they have sleeping problems and how did they rate the severity of the sleeping problems. Three types of sleep disorder have been considered to be symptoms of sleeping problems including difficulty of falling asleep, trouble of staying asleep and waking up too early in the morning. In this study, respondents who had two or three symptoms of sleeping problems have been considered to have severe sleeping problems. On the other hand, respondents only have one sleep disorder or never have sleep disorder have been considered to have no serious sleeping problems. This is because if someone had trouble falling asleep but then slept through the night, they would not be sleep deprived, whereas if someone had trouble falling asleep and then woke up early, then they would have lost considerable amounts of sleep. What is more, the frequency of sleep disorder has also been involved in the interview by asking respondents if they had sleeping problems during the interview week. The next section of questions about sleeping problems are mainly related to the usage of hypnotics like the name of the drug, the time to take it, how often did the respondents take it and how long they have taken the hypnotics etc Social engagement Social engagement acts as an index of wellbeing and a control variable for the social aspects for a few physical activities (Morgan, 1998). For social engagement, there are 20 25

27 related questions and if the answer was yes then one score would be added. Therefore the index ranges from 0 to 20. In this study, the distribution of social engagement has been divided into three groups including low, medium and high which is grouped by tertiles Psychological health In NLSAA, 14-item Symptoms of Anxiety and Depression (SAD) and 13-item Life Satisfaction Index were utilised to assess the psychological health mainly referring to depression and morale (Morgan, 1998). In this study, SAD was analysed to investigate the relationship between sleeping problems and psychological health. SAD focuses exclusively on recent symptoms and covers two parts each including seven items which are about anxiety and depression respectively (Morgan, 1988). In terms of the specific analysis in this study, individuals who had SAD scores over 6 and subscale of depression scores over 4 had been considered to be depressed, in accordance with clinical guidelines Physical health There is a 14-item health index which is an index of general physical health status and the index scored from 0 to 14 (Morgan, 1998). If the respondents have higher scores, the respondents would have more physical health problems. This health index covers many aspects of physical health including the presence or absence of eyesight, sleep, heart, stomach or foot problems; headaches, arthritis, giddiness and falls; long-term disabilities and drug and walking aid usage, contact with medical services (Morgan, 1998). In terms of this study, a modified physical health index including only 13-item health index exclude the sleep component of health has been used to investigate the association between physical health and sleeping problems. What is more, another method of assessing physical health has also been used which is the self-rated health. The results of subjective health among the respondents had also 26

28 been obtained and the physical health status had been rated as poor, fair, average, good and excellent (Morgan, 1998) Customary physical activity The customary physical activities defined in NLSAA are activities with a proximate minimum energy cost of 2 kcal/min, performed continuously for a minimum of 3 minutes and at least once a week for previous 6 weeks (Morgan, 1998). The activities have been divided into five functional categories: work-related activities, walking, outdoor activities, indoor activities and leisure activities (Morgan, 1998). The reported activities were scored as minutes per week respectively and no participation was recorded as zero (Morgan, 1998). In this study, outdoor activities like gardening, car and house maintenance, indoor activities including household activities and leisure activities like fishing are involved in analyses. The time each respondent spent in outdoor activities, indoor activities and leisure activities per week have been recorded and the distributions of these frequencies have been used to investigate the association between physical activities and sleeping problems. What is more, there are two specific scales measure the strength and joint flexibility of respondents to assess the respondents functional capabilities (Morgan, 1998). These two scales have been used to analyse the relationship between sleeping problems and physical activity as well. When analysing the data, the distribution of these two scales have divided into three groups low, medium and high respectively. 3.4 Statistical analysis The data analysis conducted in this study was bone by using Statistical Package for the Social Sciences (SPSS) version Descriptive Statistics Many tables and charts about frequency distribution are presented as a summary of the sample like age distribution, gender, social class and sleeping problems etc. Frequency 27

29 analysis of sleeping problems and other aspects related to the sleeping status among the elder people were conducted Bivariate analysis Chi-squared test Frequency table could be used to summarise categorical data which showing the proportion and number of individuals within the categories (Altman, 1991). To compare two or more proportions between two variables, many ways could be used to do this. Different ways could be utilised according to the number of categories and whether the variables are ordinal or nominal etc (Altman, 1991). Chi-squared test which uses the cross-tabulation tables could be utilised to investigate if there is a relationship between two categorical variables (Pallant, 2007). In this study, chi-squared test has been used to investigate if there are any association between demographic variables and sleeping problems variables, between different symptoms of sleeping problems and between health status variables and sleeping problems variables. A new variable has been conducted to do the analysis. All the respondents who have one or zero sleeping problem are grouped into the first group and the respondents who reported they had two or three sleeping problems which could be rather serious are grouped into the second group. This new variable could represent the status of sleeping problems among the elder people. The relationships between this new variable and other demographic variables, other variables related to physical activity and physical and psychological health variables respectively are analysed by using chi-squared test Mann-Whitney Test Mann-Whitney test is a non-parametric alternative for t test to compare data from two independent groups (Altman, 1991). Mann-Whitney test could be used for testing if there is any association between a continuous variable and a variable with two groups. Mann-Whitney test has been utilised to investigate if there is a relationship between the 28

30 13-item physical health index which exclude the sleep component and the new sleeping problems variable which divide the respondents into two groups Logistic regression models For logistic regression, a single dependent variable which is binary and the independent variables can be two or more categorical or continuous variables (Altman, 1991). After using chi-squared test, the relationship between variables related to sleeping problems and variables about health status and physical activity have been analysed primarily. For measuring the degree of relationships between the variable related to sleeping problems and other variables, logistic regression analysis has be used since this method could be utilised to measure the degree of association between a binary dependent variable and the two or more independent variables which could be categorical or continuous. According to the results of chi-squared test, several demographic, physical health, psychological health and physical activity variables were selected since those variables were found to be statistically related to sleeping problems. Those variables include age, gender, self-rated health, 13-item health index which exclude the sleep component, depression, outdoor activity, leisure activity, total effort score and total bend score. Logistic regression was conducted to investigate if any variables were independently and statistically associated with sleeping problems. The new binary variable related to sleeping problems was taken as dependent variable. The odds ratio has been calculated for each independent variable respectively which has included in the analysis. There are six models of logistic regression have been analysed in this study. Since gender is associated with sleeping problems significantly, there are logistic regression analyses among females and males separately. The respondents were divided into men and women then new models conducted to investigate the relationship between sleeping problems and other variables Survival analysis Cox regression is used widely to compare the effects of several variables on survival 29

31 (Altman, 1991). Cox regression models were conducted and utilised to investigate the relationships between sleeping problems and 21-year all cause mortality. To investigate 21 years mortality the independent variables including sleeping problems, demographic and variables about health were all taken at baseline and used a forced-entry method of selection to analyse. The dependent variable is whether the respondents were dead or alive at 31st May There are 4 models conducted for the analyses including sleeping problems (Model 1), sleeping problems and demographic variables (Model 2), variables about physical health have been added (Model 3), variables about psychological health have been added (Model 4). These four models analysed the overall data and other models analysed the data which separate men and women were also conducted and analysed. The hazard ratio of each model was calculated. 3.5 Conclusion To investigate the prevalence of sleeping problems, the analyses of frequency distribution has been done. Chi-squared test, Mann-Whitney test and logistic regression have been used to identify if there are any statistically significant relationships between sleeping problems and demographic factors, physical health and psychological health. Cox regression models have also been conducted and used to analyse if sleeping problems are associated with 21 years all-cause mortality. In this chapter, the various methods and methodologies utilised in this study have been introduced. The results of those analyses are presented and discussed in the chapter 4 and chapter 5. 4 Initial results 4.1 Introduction The discussion about the methodology utilised in this study has been done in previous chapter including the methodological overview of the Nottingham Longitudinal Study of 30