Cohort profile: The North West Adelaide Health Study (NWAHS)

Cohort profile: The North West Adelaide Health Study (NWAHS) Janet F Grant 1, Anne W Taylor 1, Richard E Ruffin 2, David H Wilson 2, Patrick J Phillips 3, Robert JT Adams 2, Kay Price 4 and the North West Adelaide Health Study Team 5 1 Population Research and Outcome Studies, SA Health, 11 Hindmarsh Square (PO Box 287), Adelaide, South Australia 5000, Australia. 2 The Health Observatory, Department of Medicine, University of Adelaide, The Queen Elizabeth Hospital, Woodville Road, Woodville, South Australia 5011, Australia. 3 Endocrine and Diabetes Service, The Queen Elizabeth Hospital, Woodville Road, Woodville, South Australia 5011, Australia. 4 University of South Australia, Adelaide, South Australia 5000, Australia. 5 The North West Adelaide Health Study Team includes Eleonora Dal Grande, Catherine Chittleborough and Tiffany Gill, Alicia Montgomerie and Sandy Pickering. Correspondence to: Janet Grant Population Research and Outcome Studies Unit Department of Health Level 8, CitiCentre Building PO Box 287, Rundle Mall Adelaide, South Australia AUSTRALIA 5000 Ph: +61 8 8226 6054 Fax: +61 8 8226 6244 Email: Janet.Grant@health.sa.gov.au Word count: 2766 (excluding tables and references) 1

How did the study come about? In westernised countries, chronic diseases have overtaken infectious diseases in terms of prevalence, and now account for approximately 60% of global deaths and almost half of the global burden of disease 1. The four chronic conditions that comprise the majority of this burden of disease are cardiovascular disease, cancer, chronic lung disease and diabetes, and they share four key risk factors: use of tobacco and alcohol, lack of physical activity and an unhealthy diet 2. In Australia, much of the information about population health is provided through cross-sectional health surveys, and from medical and hospital data collections. The North West Adelaide Health (NWAH) Study was formulated to provide much needed longitudinal data on chronic conditions and health-related risk factors in South Australia. The study commenced in 1999, following funding from The University of Adelaide Faculty of Medicine Howard Florey Centenary Grant and Division of Health Sciences Special Medicine Research Initiative, which enabled the recruitment of approximately 2500 study participants for baseline examination primarily in 2000. In 2002 03, a further 1500 study participants were invited to join the cohort for a baseline examination, funded by the Human Services Research Initiatives Projects (HSRIP) of the South Australian Department of Human Services (now SA Health). The study achieved cohort status in May 2004 with the commencement of Stage 2 of the study when participants were invited to return for their first follow-up examination, and Stage 3 of the study (the second follow-up examination) recently started in June 2008. The NWAH Study is a collaboration between SA Health, The Queen Elizabeth Hospital, the Lyell McEwin Hospital, The University of Adelaide, the University of South Australia and the Institute of Medical & Veterinary Science. The research team represents a range of disciplines including academic and clinical medicine, public health, epidemiology, social science and nursing, using quantitative and qualitative methodologies. What does it cover? The NWAH Study is a representative longitudinal study of 4060 randomly selected adults aged 18 years and over at the time of recruitment from the north-west region of Adelaide, the capital of South Australia. The sample region represents approximately half of the metropolitan area (population of approximately 1.1 million) and one-third of the population in South Australia (population of approximately 1.5 million), which has the highest elderly population of all the Australian states and territories3. The aim of the study is to provide longitudinal self-reported and measured data to assist in maximising the effectiveness of strategies for the prevention, early detection, and management of chronic conditions. Its objective is to identify and describe specific population groups at risk of developing or with undiagnosed chronic conditions, together with health-related risk factors and socio-demographic factors along a chronic disease continuum (see Figure1). The study has also fostered a number of related sub-studies on areas such as undiagnosed asthma, aortic stenosis and bone density. The study has also formed the basis for the Nutrition, Obesity, Lifestyle & Environment (NOBLE) Study, which was awarded an Australian Research Council (ARC) linkage grant in 2004 to investigate the obesity epidemic in the South Australian population, using the disciplines of psychology, medicine, public health, geography, sociology and economics. The NWAH Study recently joined the South Australian Population Health Intergenerational Research (SAPHIRe) project, with another two existing South Australian cohort studies (the Australian Longitudinal Study of Ageing and the Florey Adelaide Male Ageing Study) and a new regional cohort currently being established (the Whyalla Intergenerational Study of Health), the latter two studies established using similar methodology to the NWAH Study. The SAPHIRe project aims to identify and 2

develop common data collection items among the four studies to provide a better representation and comparability across the cohorts of the health of South Australians regarding metabolic fitness (including obesity and cardiovascular disease), respiratory health, mental wellbeing, ageing and men s health issues. As part of this collaboration, the NWAH Study will expand to collect information during Stage 3 about each participant s household including inviting, where relevant, one child under the age of 18 years for a biomedical examination. How often have they been followed up? Major stages of the study (incorporating a telephone interview, self-completed questionnaire and biomedical examination at a clinic) have been held approximately every four years: Stage 1 in 2000 and 2002 03 and Stage 2 in 2004 06. Stage 3 commenced in June 2008 and is due for completion in May 2010 (see Figure 2 for timeline). In addition, exit studies for each of the major stages have been conducted with a sub-sample of the cohort for quality control. For the main stages of the study, participants are contacted in approximately the same order each time in an effort to maintain the four year follow-up time. Each of the major stages and telephone follow-ups allows for core data collection items to be tracked over time, whilst allowing for other researchers to collect information on related research topics in collaborative projects. Who is in the sample? Overall, 4060 males and females aged 18 years and over were recruited during Stage 1 of the study (see Table 1 for demographic characteristics) (Table 1 here). The sample was a randomly selected population from the northern and western suburbs of Adelaide. All households in the northern and western areas of Adelaide with a telephone connected and a telephone number listed in the Electronic White Pages (EWP) were eligible for selection in the study. Telephone numbers that belonged to businesses, institutions and residential care facilities were excluded from the sample. However people who had their own telephone number and who were living in individual units attached to a nursing home were eligible to participate. Within each household, the person who had their birthday last and was aged 18 years and over, was selected for interview and invited to attend the clinic for a biomedical examination. The study excluded those people from a non-english speaking background who could not communicate sufficiently well with the telephone interviewer and who could not answer questions at the initial recruitment stage, although every effort was made to encourage family members to assist in translating. Trained interviewers were responsible for determining if the selected respondent within an eligible household had sufficient intellectual ability to understand the implications and requirements of participating. Following data collection, to minimise potential bias due to differing probabilities of selection in the sample, Stage 1 data were weighted by region (western and northern health regions), age group, sex and probability of selection in the household to the Australian Bureau of Statistics 1999 Estimated Resident Population4 and the 2001 Census data5. Stage 2 data was reweighted using the 2004 Estimated Resident Population6, incorporating participation in the three components, whilst retaining the original weight in the calculation. In an examination of the cohort in comparison with the eligible population, it was found that there were no major differences in terms of current smoking status, body mass index, physical activity, overall health status and proportions with current high blood pressure and cholesterol readings. Of interest is that significantly more people who reported a medium to very high alcohol risk participated in the study. There were some demographic differences with study participants more likely to be in the middle level of household income and education level7. 3

Future research will include analysis of information from approximately 750 children. This group will comprise one randomly selected child aged up to 18 years of age, living in the household of each existing adult participant. What has been measured? The study s focus is chronic conditions (including diabetes, asthma, chronic obstructive pulmonary disease, arthritis, osteoporosis, kidney health, mental health and cardiovascular disease), and modifiable health-related risk factors (such as smoking, alcohol, overweight/obesity, family history of chronic conditions, cholesterol and blood pressure). These variables are examined in relation to the demographic characteristics of participants (such as income, education, work, occupation, country of birth and marital status). The study also collects information from participants about their health care service utilisation and medications, and links this information with data received from Medicare, the Australian national medical and pharmaceutical benefits agency. An overview of data collection items, including repeat measures, is presented in Table 2 (Table 2 here). A more detailed description of the cohort, including recruitment, have been previously published8. For children, self-reported (and where relevant, proxy) measures will include levels of physical activity, quality of life and social activities. The biomedical examination for children will include (depending on age) anthropometric measures (height, weight and waist), blood pressure, a lung function test and a fasting blood test to examine cholesterol and glucose levels. Standardised, validated methods for measurements are used wherever possible. Clinic visits are conducted in the morning to maximise the efficiency of fasting blood test results and for the comfort of the study participants. Participants are sent a letter detailing their results from the study with results that are outside of the normal range highlighted for their attention. With the consent of each participant, a copy of their results are also sent to their general practitioner for their information and possible follow-up. The interim telephone follow-up interviews help to maintain ongoing contact with the study participants and allow contact details to be updated. In addition to these follow-up interviews, questionnaires have been sent for additional data collection regarding particular research issues (including possible adverse events experienced, attitudes to fast food, characteristics of participants neighbourhoods in relation to outdoor physical activity and walkability, and the current and future circumstances of life for the baby boomer generation). What is the anticipated attrition? To date, 208 participants have died and 332 participants are being tracked following loss of contact. To assist in this, participants are routinely asked at the major biomedical stages for secondary contact details for a close family member or friend in case they cannot be contacted. An annual newsletter provides information about developments with the study and enables mutual communication between the study team and participants. Birthday cards are sent every year to provide an opportunity for people to update their whereabouts with the study team. To also assist with maintaining current contact information, a change-of-address slip is included in their information pack, together with a reply paid envelope. Tracking occurs through the use of Electronic White Pages, and the South Australian and national electoral rolls. Two databases of registered deaths are used to search for possible matches with the study cohort those registered in South Australia (through the Births, Deaths and Marriages Registration Office) and those registered interstate (through the National Death Index). Consideration is currently being given to ways to supplement the cohort to maintain its effectiveness, particularly in the younger age groups where people tend to be more transient. 4

What has it found? Key findings and publications Currently, 40 papers have been published or submitted, whilst another 18 papers are being prepared. Papers are being compiled that will provide valuable incidence data on such chronic conditions as diabetes and asthma, as well as examining musculoskeletal conditions such as osteoporosis, and arthritis-related shoulder, knee and foot pain. Segmenting the cohort participants along the chronic disease continuum has allowed the characteristics of those with previously undiagnosed with asthma and diabetes to be described9,10,11. The study design has also allowed for an examination to be undertaken of self-reported versus measured data, with relation to height and weight12, and a forthcoming paper on blood pressure. A number of papers have used social epidemiology lens to examine the impact of gender and sociodemographic/socioeconomic factors on participants health and wellbeing. Reports have been published on both stages of the study, including an extensive series of 28 summary reports which compare Stage 1 to Stage 2, as well as providing associated information on demographic and quality of life in relation to a range of chronic conditions and health-related risk factors. A summary of results regarding the prevalence (and incidence where available) of a range of chronic conditions and health-related risk factors is presented in Table 3 (Table 3 here). The definitions for determining these conditions and risk factors and the cut-off scores can be found in the North West Adelaide Health Study - Stage 2 Key findings report13. [http://www.health.sa.gov.au/pros/portals/0/stage%202%20report%20for%20release.pdf]. In addition, in Stage 1, 94.0% of participants reported using a health service at least once in the last 12 months and this proportion had not significantly changed by Stage 2 (94.7%). Regarding the use of medications, one in 3 (31.5%) participants at Stage 2 reported that they were not taking any medications, whilst one in 5 (19.0%) were taking one medication, one in 7 (14.6%) were taking two medications, and one in 3 (34.8%) were taking three or more medications. Using the Short Form 36 (SF-36), the study found that one in six adults (18.0%) reported experiencing fair or poor overall health, while 82.0% reported experiencing good, very good, or excellent overall health at Stage 1. The total proportion reporting fair or poor overall health decreased to 15.2% at Stage 2, although 7.0% of those reporting good to excellent health at Stage 1 were experiencing fair or poor health at Stage 25. Stage 3 of the study, currently in progress, has maintained much of its core data collection focus. Self-report information being sought has expanded to incorporate sleep habits, including symptoms of sleep apnoea, knowledge about cardiovascular disease and risk factors, nutrition (including household food habits) and the household environment, including information about family pets. The biomedical examination has been expanded to include health literacy and a wider range of blood and urine tests, including a sample of blood for future DNA research. What are the main strengths and weaknesses? The study s main strength comes from its wealth of measured and self-reported information on multiple chronic conditions which, together with the data collected on a wide range of risk factors and sociodemographic variables, provides a rich data source that can be analysed using many different lenses - including by condition, age, gender, and ethnicity. Further, the cohort study design allows for the characteristics of populations either at risk or currently undiagnosed with particular chronic conditions and/or risk factors to be described and targeted for health planning and promotion purposes. Additional strengths of the study include its ability to conduct repeat measures of core conditions, whilst incorporating cross-sectional research on various health-related subjects. As mentioned previously, the study is developing data linkage with lifecourse health-related datasets, including early 5

childhood and hospital admission data. From an methodological viewpoint, the study allows for issues to be examined such as refusal to participate and respondent bias. Its sound epidemiological base, large randomly selected population and good response rates (see Figure 3) allows for its generalisability: firstly for the local communities it represents, secondly for South Australians and thirdly for the wider Australian population, whilst providing useful research results for the international public health community. Collaborations between researchers in all three South Australian universities have been maintained, and new research projects are being developed (such as data linkage with other studies and neighbouring regions) as the need for evidence regarding various public health issues is identified. These researchers join the existing academic and clinical staff, and bring their expertise in a wide range of disciplines, including spatial information and health economics. Can I get access to the data? Where can I find out more? The data are stored and maintained electronically within the study s epidemiological and administrative centre in the Population Research & Outcome Studies (PROS) Unit at SA Health (South Australian Government Health Department). Requests for deidentified data or questions about the study can be directed either to the Chief Investigator (anne.taylor@health.sa.gov.au) or the Study Co-ordinator (janet.grant@health.sa.gov.au). Requests for sub-studies, collaborations or datasets are considered and approved where appropriate by the study s Management Committee. To assist with dissemination to study participants, and also the wider Australian community and health professionals worldwide, a dedicated website (http://www.nwadelaidehealthstudy.org) was developed, highlighting aspects of the study including the study team, results, and frequently asked questions. The website also provides links to all study reports, and conference presentations and posters, as well as an online enquiry form that generates an email to the study team, for questions or notification of change of contact details. Further information about the study, (including downloadable reports, conference presentations and journal articles) is available via the PROS Unit website (http://www.health.sa.gov.au/pros/). Acknowledgements The study team are most grateful for the generosity of the cohort participants in the giving of their time and effort to the study. The study team also is very appreciative of the work of the clinic, recruiting and research support staff for their substantial contribution to the success of the study. 6

Table 1 Profile of participants in the North West Adelaide Health Study Variable n % Sex Male 1988 49.0 Female 2072 51.0 Age group (years) 18 34 1411 34.8 35 54 1437 35.4 55 74 878 21.6 75 90 335 8.2 Area of residence Western suburbs 1853 45.6 Northern suburbs 2207 54.4 Highest education level obtained Secondary 1751 43.1 Trade/Apprenticeship/Certificate/Diploma 1641 40.4 Bachelor degree or higher 475 11.7 Not stated 193 4.8 Annual gross household income Up to $20,000 902 22.2 $20,001 40,000 1008 24.8 $40,001 60,000 899 22.2 More than $60,000 992 24.4 Not stated 258 6.4 Aboriginal or Torres Strait Islander origin Yes 20 0.5 No 3548 87.4 Not stated 492 12.1 Country of birth Australia 2865 70.6 UK or Ireland 645 15.9 Europe, Asia & other 524 12.9 Not stated 25 0.6 Marital status Married or living with partner 2525 62.2 Separated/Divorced 331 8.1 Widowed 232 5.7 Never married 940 23.1 Not stated 32 0.8 Work status Full time employed 1537 37.9 Part time/casual employed 728 17.9 Unemployed 173 4.3 Home duties/retired 1239 30.5 Student/Other 333 8.2 Not stated 49 1.2 Receive pension from Department of Social Security Yes 1286 31.7 No 2698 66.5 Don t know/not stated 75 1.8 Total 4060 100.0 7

Table 2 Summary of data collection items from the North West Adelaide Health Study CORE MEASURES (included in all 3 stages) REPEATED MEASURES (2 stages) Conditions: asthma, bronchitis, emphysema, diabetes, cardiovascular disease (heart attack, stroke, angina), mental health (anxiety, depression, stress-related, any other mental health conditions) Risk factors: smoking, alcohol, high cholesterol, high blood pressure, height, & weight (for body mass index), waist and hip circumference, quality of life (SF36), physical activity (National Health Survey & Active Australia), health care utilisation, family history (diabetes, heart disease, stroke), lung function, lipids (cholesterol, triglycerides, glucose, HbA1c) Demographics: education, household income, marital status, work status, pension benefit Conditions: cardiovascular disease (TIA/mini-stroke), osteoporosis, arthritis, musculo-skeletal (low back, hips, knees, feet, shoulders, hands), injury, mental health depression (CES-D), kidney health (urine albumin & creatinine) Risk factors: family history (osteoporosis) Demographics: occupation, family structure ADDITIONAL SINGLE MEASURES Stage 1: Telephone Follow Up 1: Stage 2: Telephone Follow Up 2: Risk factors: skin allergies, Demographics: age, date of birth, sex, number of people <18 and 18+ in household, country of birth, Aboriginal/Torres Strait Islander status Supplementary information including asthma and diabetes Conditions: mental health (GHQ12), arthritis (shoulder movements; hand photo & grip strength) Risk factors: sunlight, menopause Supplementary information including demographics (occupation, study and other life commitments), lifecourse information (parents country of birth, etc), neighbourhood migration, lifestyle, nutrition, psychological distress (K10) Stage 3: SUB-STUDIES Conditions: gout Risk factors/other: waist circumference, family history (high blood pressure, body type of biological parents, asthma), quality of life (AQOL), sleep and sleep apnoea, mastery and control, major health events, cardiovascular knowledge, household food habits and environment, other people in household, kindergarten attendance, carers role, nutrition (food frequency questionnaire), blood sample (DNA, c-reactive protein, complete blood exam & biochemistry), exhaled nitric oxide, exhaled carbon monoxide, health literacy Demographics: housing situation, money situation Adverse health events Osteoporosis (DEXA) of those 50+ years Neighbourhood characteristics Baby Boomers Plain text indicates self-reported measures; italicised text indicates both self-reported and biomedical measures; bold text indicates biomedical measures. 8

Table 3 Health Study Summary of results from Stage 1 and Stage 2 of the North West Adelaide Variable Stage 1 Prevalence (%) Stage 2 Prevalence (%) Annual incidence no. of people per 1000 of adult pop Chronic conditions Asthma 12.5 16.2 24.6 Chronic obstructive pulmonary disease 3.9 4.8 6.1 Cardiovascular disease 6.2 5.7 5.6 Diabetes 6.6 7.2 6.8 Mental health 13.6 16.1 22.9 Stage 2 only Kidney health - Chronic kidney disease - 11.5 - - Macro/microalbuminuria - 5.5 - Mental health - Depression - 12.4 - - Psychological wellbeing (mild/ - 11.1 moderate) - Psychological wellbeing (high/severe) - 13.5 Musculoskeletal - Arthritis - 21.4 - - Foot pain - 17.6 - - Hip pain - 9.2 - - Hip stiffness - 7.7 - - Knee pain - 16.0 - - Low back pain/aching - 30.3 - - Osteoporosis - 3.6 - - Osteopoenia - 15.0 - - Shoulder pain/stiffness - 22.3 - Modifiable risk factors Alcohol (intermediate to very high risk) 6.1 5.7 9.6 (High) Blood pressure 26.8 25.8 33.6 (High) Cholesterol 36.3 40.6 45.4 Obesity - Body mass index 27.0 29.3 18.6 - Waist circumference 58.1 63.9 30.8 - Waist hip ratio 16.4 23.3 34.2 Physical activity sedentary 28.1 28.9 41.5 Smoking 24.4 20.1 6.9 9

Figure 1 Chronic disease continuum Improved health status / Deteriorating health status Not at risk At risk Previously undiagnosed Diagnosed without comorbidity Diagnosed with comorbidity Death Prevention Delay/Early Detection Prevention/Delay/Early Detection/Care 10

Figure 2 Timeline of the North West Adelaide Health Study STAGE 1 Timeline Jan 2000 Feb to Nov 2000 March 2002 Sept 2002 to June 2003 Phases of the study Eligible random, representative Electronic White Pages (EWP) sample, north-west Adelaide Study recruitment of adults aged 18 years and over, using Computer Assisted Telephone Interview (CATI) system Attended clinic (Phase 1A n=2523) Telephone Follow Up 1 (n=2231) Additional attended clinic (Phase 1B n=1537) STAGE2 May 2004 to Feb 2006 Second major follow-up (n=3563) including clinic assessment of cohort (n=3206) July to Nov 2007 Telephone Follow Up 2 (n=3622) STAGE 3 June 2008 to May 2010 Third major follow-up including clinic assessment of cohort 11

Figure 3 Response rate for stages of the North West Adelaide Health Study Initial sample n=10,096 Eligible sample n=8213 Exclusions (% of sample) Ineligible sample n=1883 (18.7%) Non-contact n=215 (2.6%) Non-connected numbers Non-residential numbers Fax/modem connections STAGE 1 Interviewed n=5850 Did not do interview n=2148 (26.2%) Did not attend clinic n=1790 (30.6%) Attended clinic n=4060 Attended clinic/interviewed = 69.4% participation rate Attended clinic/eligible = 49.4% response rate Tel Follow-Up 1 n=3622 Participated/eligible sample = 91.7% response rate STAGE 2 n=4060 Ineligible (died) n=100 (2.5%) Eligible sample n=3957 Unable to contact n=233 (5.9%) No information n=160 (4.3%) Interviewed and/or completed ques n=3564 Information/eligible = 90.1% response rate Did not attend clinic n=854 (21.6%) Attended clinic Attended clinic/eligible 12

n=3206 = 81.0% response rate Tel Follow-Up 2 n=2996 Participated/eligible sample = 79.7% response rate 13

References 1 2 3 4 5 6 7 8 9 World Health Organization: World Health Report 2003: Shaping the future. Geneva: WHO, 2003. Yach D, Hawkes C, Gould CL, Hofman KJ: The global burden of chronic diseases: overcoming impediments to prevention and control. JAMA 2004; 291: 2616-2622. Australian Bureau of Statistics: Population by age and sex, Australian States and Territories. Canberra: ABS, 2006. Australian Bureau of Statistics. Population by age and sex, South Australia, 30 June 1999. Canberra: ABS, 2000. Australian Bureau of Statistics. Census of Population and Housing, Selected Social and Housing Characteristics for Statistical Local Areas, South Australia, 2001. Canberra: ABS, 2002. Australian Bureau of Statistics. Population by Age and Sex, South Australia, June 2004. Canberra: ABS, 2005. Taylor AW, Dal Grande E, Gill T, Chittleborough C, Wilson DH, Adams RJ, Grant JF, Phillips P, Ruffin RE & the North West Adelaide Health Study Team: Do people with risky behaviours participate in biomedical cohort studies? BMC Public Health 2006; 6:11. Available at http://www.biomedcentral.com/1471-2458/6/11. Grant JF, Chittleborough CR, Taylor AW, Dal Grande E, Wilson DH, Phillips PJ, Adams RJ, Cheek J, Price K, Gill T, Ruffin RE and the North West Adelaide Health Study Team. The North West Adelaide Health Study: methodology and baseline segmentation of a cohort along a chronic disease continuum. Epidemiol Perspect Innovat 2006; 3:4. Available at http://www.epi-perspectives.com/content/3/1/4. Adams R, Wilson D, Appleton S, Taylor A, Dal Grande E, Chittleborough C, Ruffin R. Underdiagnosed asthma in South Australia. Thorax 2003; 58(10): 846-50. 10 Wilson D, Appleton S, Adams R, Ruffin R. Undiagnosed asthma in older people: an underestimated problem. Med J Aust 2005; 183(1): S20-S22. 11 Chittleborough C, Baldock K, Taylor A, Phillips P. Health status assessed by the SF-36 along the diabetes continuum in an Australian population. Qual Life Res 2006; 15(4): 687-94. 12 Taylor AW, Dal Grande E, Gill TK, Chittleborough CR, Wilson DH, Adams RJ, Grant JF, Phillips PJ, Appleton S, Ruffin RE. How valid are self reported height and weight? A comparison between CATI self-report and clinic measurements using a large representative cohort study. Aust N Z J Public Health 2006; 30(3): 238-46. 13 Population Research & Outcomes Studies Unit: North West Adelaide Health Study: Stage 2 Key findings. Adelaide, SA Health, 2007. Available at http://www.health.sa.gov.au/pros/portals/0/stage%202%20report%20for%20release.pdf. 14