Women Living Alone Have an Increased Risk to Develop Diabetes, Which Is Explained Mainly by Lifestyle Factors

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1 Metabolic Syndrome/Insulin Resistance Syndrome/Pre-Diabetes O R I G I N A L A R T I C L E Women Living Alone Have an Increased Risk to Develop Diabetes, Which Is Explained Mainly by Lifestyle Factors JONAS LIDFELDT, MD, PHD 1 CHRISTINA NERBRAND, MD, PHD 1 2 GÖRAN SAMSIOE, MD, PHD CARL-DAVID AGARDH, MD, PHD 2 OBJECTIVE The purpose of this study was to assess the role of household conditions for the progression to diabetes in women with impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS A total of 461 women, aged years, with IGT defined by an oral glucose tolerance test, had baseline advice on physical exercise, diet, smoking, and alcohol habits. Physical examination, blood tests, and questionnaires were completed at baseline and after 2.5 years. Household status was categorized into living alone or with a partner, other adults, or children. RESULTS Women living alone had a 2.68-fold increased risk (95% CI ) of developing diabetes after adjustments for biological risk factors. Further stepwise adjustments for education, occupation, subjective mental health, exercise, diet, and alcohol showed remaining significant odds ratios (ORs), decreasing from 3.26 ( ) to 3.03 ( ). However, when smoking status was added, the OR became nonsignificant, 2.07 ( ). More women who lived alone smoked and did not reduce their daily cigarette consumption compared with women in other household conditions. At follow-up, women living alone had reduced their alcohol consumption and were more often abstainers and fewer had healthy dietary habits or had improved their diet. Physical exercise did not differ among the groups. Separate analyses of any other household status did not show any excess risk for development of diabetes. CONCLUSIONS Women living alone had a higher risk to progress from IGT to diabetes, mostly explained by smoking, alcohol, and dietary habits. Household conditions should be accounted for when assessing future risk for diabetes. Diabetes Care 28: , 2005 Biological risk markers for type 2 diabetes, such as obesity and insulin resistance, are well known (1), and short-term results have described positive effects of changes in lifestyle in subjects with impaired glucose tolerance (IGT) (2,3). To fully understand the causes for the increase in IGT and diabetes (4), a broader perspective that considers social and psychological aspects is needed. Low education and social inequity have been associated with the metabolic syndrome (5,6). Depressive symptoms have been shown to be associated with increased diabetes incidence in women (7), and depression is more pronounced among women who are widows or divorced (8). The rate of divorces has increased during the last 100 years in the western world as well as in Sweden and has doubled the past decade among those 70 years (9). Individuals living alone after divorce or being widowed or who have never married have an increased mortality risk (9), only partly explained by higher rates of suicide (10). Living conditions according to household status may be a psychosocial stressor in daily life that could have an From the 1 Department of Clinical Sciences, Lund University, Malmö, Sweden; and the 2 Department of Clinical Sciences, Lund University, Lund, Sweden. Address correspondence and reprint requests to Jonas Lidfeldt, MD, PhD, Department of Clinical Sciences, Community Medicine, Malmö University Hospital, SE Malmö, Sweden. jonas.lidfeldt@ med.lu.se. Received for publication 16 April 2005 and accepted in revised form 23 June Abbreviations: HOMA-IR, homeostasis assessment model of insulin resistance; IGT, impaired glucose tolerance; NGT, normal glucose tolerance; OGTT, oral glucose tolerance test. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances by the American Diabetes Association. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. impact on health and outcome of diseases, such as diabetes. We have previously described a subgroup of welleducated single women with a more favorable lifestyle (11), whereas women living alone in general had impairments in healthiness and glucose metabolism (12). However, detailed analyses of the impact of household status and lifestyle conditions on the risk of diabetes have not previously been studied. The aim of this longitudinal study was to assess the role of household conditions for the development of type 2 diabetes in middle-aged and older women with IGT and to what extent differences in lifestyle may be explanatory factors. RESEARCH DESIGN AND METHODS Screening was performed in in 6,917 women aged years, living in a defined area of Southern Sweden, and identified through a population register comprising all 10,766 inhabitants. Informed consent was obtained, and the ethics committee at Malmö/Lund approved the study. The baseline physical examination included body weight, BMI, waist-to-hip ratio, and the average of two blood pressure recordings in the seated position after 15 min of rest. Blood glucose and serum levels of triglycerides and total cholesterol were measured in capillary whole blood (Cholestech LDX; Cholestech, Hayward, CA). Hormonal assays of serum fasting insulin and leptin were performed using an enzyme-linked immunosorbent assay (DRG, Marburg, Germany). Insulin resistance was expressed through the homeostasis assessment model of insulin resistance (HOMA-IR) (13). A questionnaire was used at baseline and at follow-up regarding medical history, perimenopausal status, pharmacological treatment, family history of diabetes, physical activity, dietary, alcohol and smoking habits, marital status, household, education, occupation, and mental health. At baseline, 3,593 subjects with one or more features of the metabolic syndrome were identified, and a 75-g oral glucose tolerance test (OGTT) was per- DIABETES CARE, VOLUME 28, NUMBER 10, OCTOBER

2 Risk for diabetes for women living alone Table 1 Household status in relation to OGTT at follow-up among 461 women with IGT at baseline formed in the fasted state. The positive cutoff values were BMI 30 kg/m 2, waistto-hip ratio 0.9, systolic blood pressure 160 and/or diastolic blood pressure 95 mmhg, capillary blood glucose level 8.0 mmol/l, or serum triglyceride level 2.3 mmol/l; family history of diabetes (parents/siblings) and treatment for hypertension or hyperlipidemia were also considered. A control group without positive screening was also examined with an OGTT. The procedure efficiently identified subjects with IGT or diabetes (14). In all, 626 women had IGT and received lifestyle advice regarding exercise, dietary, smoking, and alcohol habits individually for 1 h and after the examination were invited to a 2.5-year follow-up with a new OGTT and measurement of BMI, blood pressure, fasting insulin, and leptin. From the initial group, 461 returned for the follow-up examination (12). No in-between examinations were performed. Fasting insulin and leptin were randomly analyzed in 153 of the 461 women who had IGT and returned for the follow-up study. No differences in baseline biological data were seen among the 461 participating women and the nonparticipants or among the random group of women from whom hormones were analyzed and remaining women with IGT. All NGT I-IFG IGT Diabetes P (NGT vs. diabetes) n Household (%) Living alone */0.029 With a partner With children With a partner and children With other adults Data are from two-sided 2 tests. *Analysis among five stages of household status (4 df) and among women living alone and in a group including all other stages of household status (1 df). I-IFG, isolated impaired fasting glucose. Social and psychosocial conditions and lifestyle Household status included women living alone, with a partner, with children, with a partner and children, or with other adults. Marital status meant married, unmarried, divorced, or widowed. Education was categorized into comprehensive school (9 years), upper secondary school (12 years), or university degree. Occupational status referred to full-time or part-time occupation, being a housewife, retired, unemployed, long-term sick-listed, or having a disability pension. Subjective mental health was measured by the validated Gothenburg Quality of Life instrument (15), which refers to the World Health Organization definition of health. Mental well-being was assessed in seven steps with five questions on mood, energy, endurance, self-esteem, and sleep. The mean sum score of estimations from very bad (1) to excellent, could not be better (7) was calculated. Ten mental symptoms regarding restlessness, difficulty to relax, nervousness, impaired concentration, sleeping disturbance, irritability, exhaustion, general fatigue, crying easily, and depression were answered with yes or no depending on whether the woman had any of these symptoms during the last 3 months. The total number of yes answers was used in analyses. Self-reported dietary habits were based on four questions regarding fat, fibers, fruits/vegetables, and sweets/ carbohydrates, with three sublevels from unhealthy to healthy, and on a food questionnaire, which ensured that the basic questions discriminated between unhealthy and healthy diets. Women defined as having healthy dietary habits were those indicating a healthy pattern on at least three of four basic questions with no indications of an unhealthy pattern. The subjects summarized their leisure time exercise during the last year into hardly any activity, 30 min/week, min/week, min/week, and 120 min/week of jogging and equivalent activities. Weekly consumption of wine, beer, and spirits was converted into grams of alcohol and divided into no consumption, 83 g/week, and 84 g/week. Smoking was categorized by lifetime consumption of pack-years. One pack-year corresponded to 20 cigarettes/ day/year. Subjects were divided into never smokers ( 1 pack-year) and past and current smokers ( 1 pack-year). Statistics Calculations were performed using SPSS Values are given as means SD. The 2 test was used to analyze differences in proportions for categorical variables, and the independent-samples t test or paired-samples t test was used for continuous variables. Multiple logistic regression analyses were used to evaluate the influence of household status on the risk of developing diabetes and to reverting to normal glucose tolerance (NGT). Women living alone were compared with the remaining group of women with any other household condition. Multivariate adjustments in different blocks were entered stepwise. The fit of the models was analyzed by calculation of Hosmer- Lemeshow goodness-of-fit statistics, and statistics for the overall models was analyzed by using Cox and Snell R 2 and Nagelkerke R 2. P values 0.05 were considered statistically significant. RESULTS Household status Of 461 women with IGT at baseline, 175 (38%) had NGT at follow-up, 9 (2%) had impaired fasting glucose, 222 (48%) had IGT, and 55 (12%) progressed to diabetes. Sixty-six women (14.3%) lived alone, 327 (71.1%) lived with a partner without children, 13 (2.7%) lived with children only, 53 (11.5%) lived together with a partner and children, and 2 (0.4%) lived with other adults. There were no differences in household status between women who developed diabetes and those who changed to NGT when each household status was simultaneously analyzed. However, more women who lived alone progressed to diabetes compared with those with other household conditions combined (P 0.029) (Table 1). Corresponding analyses for each other household status, compared with those for the remaining women, showed no differences in progression to diabetes (P ). Among women living alone, 32 (48.5%) were divorced, 15 (22.7%) were unmarried, 12 (18.2%) were widowed, and 7 (10.6%) were married but not living with their husband. There was no difference in rates of women progressing to diabetes according to their marital status (P 0.59). At follow-up, 17 previously cohabiting women were living 2532 DIABETES CARE, VOLUME 28, NUMBER 10, OCTOBER 2005

3 Lidfeldt and Associates Table 2 Descriptive clinical variables according to baseline household status alone, whereas 6 had changed from living alone to living with a partner (n 5) or parent (n 1). Living alone Other household status* P value n Age (years) Baseline Follow-up Follow-up time (years) Serum fasting insulin (pmol/l) Baseline P value Follow-up HOMA-IR Baseline P value Follow-up Serum fasting leptin (ng/ml) Baseline P value Follow-up BMI (kg/m 2 ) Baseline P value Follow-up Data are means SD. *Living with a partner, children, or other adults. Independent-samples t test. Analyses of a random sample of every third subject ( women) who performed the test both at baseline and follow-up. Paired-samples t test. HOMA-IR fasting insulin fasting glucose/22.5. Baseline variables and changes at follow-up The 66 women living alone and the 395 remaining women did not differ in education (P 0.49), occupation (P 0.53), subjective mental well-being (P 0.56), or mental symptoms (P 0.39), and no differences were seen in age at baseline or follow-up or in follow-up time (Table 2). Fasting glucose did not differ at baseline (P 0.25) but was higher at follow-up in women living alone compared with the remaining women (P 0.023). No differences were seen at baseline or at follow-up in 2-h blood glucose level (P 0.99 and P 0.17) or in systolic (P 0.72 and 0.71) or diastolic blood pressure (P 0.90 and 0.34). Among women living alone, systolic (P 0.046) and diastolic (P 0.001) blood pressure had become lower at follow-up. In the remaining women, systolic (P 0.001) and diastolic (P 0.001) blood pressure, as well as fasting (P 0.017) and 2-h (P 0.001) blood glucose level, had decreased (data not shown). There were no differences in fasting insulin or leptin levels or in HOMA-IR at baseline or follow-up between the two groups (Table 2). However, leptin had increased at follow-up, both among women living alone (P 0.003) and among the other women (P 0.001). BMI was unchanged among women living alone, whereas it was lower at follow-up among the remaining women (P 0.046). No differences were seen in exercise at baseline, and nearly equivalent rates of women in both groups had changed their weekly exercise habits at follow-up (Table 3). At baseline, there was no difference in diet. At follow-up, fewer women living alone had a diet regarded as healthy (P 0.001), and only 1.5% had improved their dietary habits and 86.4% had an unchanged poor diet. Corresponding figures among the other women were 18.3 and 61.7% (P 0.001). More women living alone had high intake of saturated fat and carbohydrates (data not shown). Alcohol consumption did not differ at baseline, but more women who lived alone were abstainers at follow-up (P 0.045). The amount of weekly alcohol intake was lower at baseline (P 0.025) and follow-up (P 0.013) for women living alone, and they reduced their consumption (P 0.036), whereas habits remained unchanged among the other women. Fewer women living alone had never smoked and more were current smokers at baseline (P 0.002) and follow-up (0.006). Women living alone and who smoked consumed more cigarettes per day at baseline (P 0.039) and had not changed the daily amount at followup, in contrast to the reduction seen in cohabiting smoking women (P 0.030). Risk estimates Women living alone had a 2.47-fold increased risk of developing diabetes after adjustment for age (95% CI ) and a 2.68-fold increased risk ( ) after adjustments for age, follow-up time, BMI, 2-h blood glucose at baseline, serum triglyceride levels, total cholesterol level, blood pressure, family history of diabetes, and perimenopausal status (Table 4). The risk increased to 3.26 ( ) when education and occupation were added to the analysis. The risk increased if education and occupation were added simultaneously as well as separately. Further adjustments for subjective mental health, physical exercise, dietary habits, and alcohol consumption showed remaining significant odds ratios (ORs), decreasing from 3.18 ( ) to 3.03 ( ). When smoking status was added, the OR became nonsignificant (2.07 [ ]). Also, the risk was attenuated to null when smoking was included without adjustments for exercise, diet and alcohol (2.29 [ ]). P values for smoking were at nonsignificant levels in these models, both with (P 0.15) and without (P 0.13) simultaneous adjustments for the three other lifestyle variables. Smoking was not related to diabetes incidence (P 0.28) after adjustments for age and household only. The Hosmer-Lemeshow values ranged from to 0.848, the Cox and Snell R 2 ranged from to (data not shown), and the Nagelkerke R 2 ranged from to in models with P CONCLUSIONS This prospective study showed that household conditions influenced the transition from IGT to diabetes. Middle-aged and older women with IGT and living alone had a higher risk of developing diabetes. Negative health effects from living alone may potentially be mediated through social and mental conditions. There is a known socioeconomic gradient, often attributed to a low level of education, in health outcomes such as cardiovascular disease (16), although it has not been fully de- DIABETES CARE, VOLUME 28, NUMBER 10, OCTOBER

4 Risk for diabetes for women living alone Table 3 Lifestyle variables according to baseline household status Living alone Other household status* P value n Leisure time exercise (%) Baseline Hardly any activity min/week min/week min/week min/week Changes at follow-up Reduced Unchanged Increased Dietary habits (%) Healthy diet Baseline Follow-up Changes at follow-up Unchanged healthy Improved Deteriorated Unchanged poor Alcohol consumption (%) Baseline Abstainers g/week g/week Follow-up Abstainers g/week g/week Total sum (g/week) Baseline 43.2 (40.9) 59.9 (62.8) P value# Follow-up 33.0 (39.0) 61.1 (69.1) Smoking (%) Baseline Never Past Current Follow-up Never Past Current Number of cigarettes/day Baseline 14.7 (7.4) 9.9 (6.4) P value# Follow-up 11.8 (10.1) 7.6 (7.3) 0.15 *Living with a partner, children, or other adults. Independent-samples t test. Self-reported exercise/week, corresponding to jogging and equivalent activity. Subjects living alone increased their intake of fat above all and had unchanged high intake of carbohydrates compared with the other subjects. Among consumers. #Paired-samples t test. scribed in diabetes. Low-paid labor is more common among women (17), making women without a supporting partner especially susceptible for socioeconomic strain. Work stress and a low sense of coherence in middle-aged women have been associated with type 2 diabetes (18). In this study, adjustments for education and occupation did not eliminate the risk in women living alone but instead augmented the risk. This may be explained by that fact that a relatively high proportion of women living alone and who had a university degree and worked developed diabetes. A limitation was the rather finite definition of occupational status as being capable of working and having work outside home or not. Our findings showed that low subjective mental health explained some of the differences between women living alone and the other women. This finding is consistent with other reports showing that diabetes is associated with lower well-being (19) and that depression is more common in patients with type 2 diabetes (7). We did not separate replies to questions on depression in this analysis but have previously shown that poor self-rated health is associated with treatment for depression (20), indicating that the Gothenburg Quality of Life instrument (21) used in the Women s Health in the Lund Area study is reliable. We have also shown that women who lived alone had a higher risk for severe mental symptoms (21). The present data are in line with previous results showing that living alone was associated with neglect of self-care in insulin-dependent diabetes (22). The importance of different psychosocial conditions in women living alone seems to explain the increased risk of progression to diabetes only to some degree. Instead, this risk was mostly associated with smoking, dietary, and alcohol habits at baseline and modifications during the follow-up period. There were more current smokers among women living alone. Also, these women consumed more cigarettes, and the importance of smoking for the outcome of diabetes in women living alone was the most consistent finding of the lifestyle variables. Smoking has in other studies been linked to type 2 diabetes, probably due to increased insulin resistance (23). However, smoking in this study was not independently associated with diabetes and cannot be regarded as important as the status of living alone. Thus, living alone seems to be a better predictor of diabetes. A well-balanced diet and a decrease in body weight prevent progression to diabetes in patients with IGT (2,3). BMI did not differ at baseline or follow-up, but cohabiting women reduced their BMIs slightly during the follow-up period. No differences were seen in physical exercise at baseline, and both groups had altered their weekly exercise habits to the same degree at follow-up. Still, exercise seemed 2534 DIABETES CARE, VOLUME 28, NUMBER 10, OCTOBER 2005

5 Lidfeldt and Associates Table 4 Relative risks of type 2 diabetes at 2.5 years follow-up among women who had IGT at baseline and were living alone OR (95% CI) P value Hosmer- Lemeshow Nagelkerke R 2 Age adjusted 2.47 ( ) MV* 2.68 ( ) MV education and occupation 3.26 ( ) MV education and occupation mental health 3.18 ( ) MV education and occupation mental health exercise 3.11 ( ) MV education and occupation mental health diet 3.09 ( ) MV education and occupation mental health alcohol 3.13 ( ) MV education and occupation mental health smoking# 2.29 ( ) MV education and occupation mental health exercise and diet 3.01 ( ) MV education and occupation mental health exercise, diet, 3.03 ( ) and alcohol MV education and occupation mental health exercise, diet, alcohol, and smoking 2.07 ( ) The fit of the models was analyzed by Hosmer-Lemeshow and Nagelkerke R 2 statistics. *Multivariate analysis (MV) adjusted in logistic regression for age, follow-up time, BMI, 2-h blood glucose level at baseline, serum levels of triglycerides, total cholesterol, blood pressure, family history of diabetes, perimenopausal status (premenopausal, postmenopausal with hormone use, or postmenopausal without hormone use). Three categories of education ( 9 years, 12 years, or university degree) and two categories of work (full- or part-time work or not working). Scores on mental well-being and mental symptoms, see RESEARCH DESIGN AND METHODS for details. Five categories of physical weekly exercise (hardly any activity, 30 min, min, min, or 120 min of jogging or equivalent activity). Dietary habits categorized into having or not having a healthy diet as defined in RESEARCH DESIGN AND METHODS. Three categories of weekly alcohol consumption (0, 83, or 84 g). #Smoking was categorized as never smoked, past smoking, or current daily smoking. to have a slight impact on the risk estimates for the increased risk among women living alone. Weight reduction and regular physical activity improve glucose tolerance by increased insulin release and improved insulin sensitivity (24). However, we could not find any difference in insulin levels or insulin resistance, which might be explained by the small number of samples or short follow-up time. Serum leptin levels increased in all women, but without any differences between the two groups. The increase was somewhat bigger in women living alone, which could be a sign of augmented insulin resistance, despite unchanged insulin levels that usually correlate positively with leptin (25). Leptin has been shown to be positively associated with many metabolic variables and insulin resistance, but the levels have been similar in subjects with and without diabetes (26), which may support the results in the present study. Among women living alone, there were more alcohol abstainers and lower consumption among users, which seemed to have a negative impact on glucose tolerance. Moderate alcohol consumption has been shown to decrease the risk of diabetes (27), possibly related to long-term effects on glucose metabolism of liver transformations (28). The relatively small total numbers of subjects and large difference in sample size between the two studied groups implies low power to detect real differences. However, because this was an observational study, these were the subjects who were available to us. The analyses of goodness-of-fit and statistics for the overall models showed satisfactory fit of the presented models. In summary, middle-aged and older women with IGT and living alone had a higher risk of progression to diabetes, mostly due to their smoking, dietary, and alcohol habits. Leisure time exercise and other psychosocial conditions had less influence on the outcome. Acknowledgments This study was supported by Region Skane Sweden. References 1. 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