Christopher Stevenson

The number of years lived with obesity and the risk of all-cause and cause-specific mortality

BACKGROUND The role of the duration of obesity as an independent risk factor for mortality has not been investigated. The aim of this study was to analyse the association between the duration of obesity and the risk of mortality. METHODS A total of 5036 participants (aged 28-62 years) of the Framingham Cohort Study were followed up every 2 years from 1948 for up to 48 years. The association between obesity duration and all-cause and cause-specific mortality was analysed using time-dependent Cox models adjusted for body mass index. The role of biological intermediates and chronic diseases was also explored. RESULTS The adjusted hazard ratio (HR) for mortality increased as the number of years lived with obesity increased. For those who were obese for 1-4.9, 5-14.9, 15-24.9 and ≥ 25 years of the study follow-up period, adjusted HRs for all-cause mortality were 1.51 [95% confidence interval (CI) 1.27-1.79], 1.94 (95% CI 1.71-2.20), 2.25 (95% CI 1.89-2.67) and 2.52 (95% CI 2.08-3.06), respectively, compared with those who were never obese. A dose-response relation between years of duration of obesity was also clear for all-cause, cardiovascular, cancer and other-cause mortality. For every additional 2 years of obesity, the HRs for all-cause, cardiovascular disease, cancer and other-cause mortality were 1.06 (95% CI 1.05-1.07), 1.07 (95% CI 1.05-1.08), 1.03 (95% CI 1.01-1.05) and 1.07 (95% CI 1.05-1.11), respectively. CONCLUSIONS The number of years lived with obesity is directly associated with the risk of mortality. This needs to be taken into account when estimating its burden on mortality.

Diabetes and risk of physical disability in adults: a systematic review and meta-analysis

BACKGROUND According to previous reports, the risk of disability as a result of diabetes varies from none to double. Disability is an important measure of health and an estimate of the risk of disability as a result of diabetes is crucial in view of the global diabetes epidemic. We did a systematic review and meta-analysis to estimate this risk. METHODS We searched Ovid, Medline, Embase, Cochrane Library, and Cumulative Index to Nursing and Allied Health Literature up to Aug 8, 2012. We included studies of adults that compared the risk of disability-as measured by activities of daily living (ADL), instrumental activities of daily living (IADL), or mobility-in people with and without any type of diabetes. We excluded studies of subpopulations with specific illnesses or of people in nursing homes. From the studies, we recorded population characteristics, how diabetes was diagnosed (by doctor or self-reported), domain and definition of disability, and risk estimates for disability. We calculated pooled estimates by disability type and type of risk estimate (odds ratio [OR] or risk ratio [RR]). RESULTS Our systematic review returned 3224 results, from which 26 studies were included in our meta-analyses. Diabetes increased the risk of mobility disability (15 studies; OR 1.71, 95% CI 1.53-1.91; RR 1.51, 95% CI 1.38-1.64), of IADL disability (ten studies; OR 1.65, 95% CI 1.55-1.74), and of ADL disability (16 studies; OR 1.82, 95% CI 1.63-2.04; RR 1.82, 95% CI 1.40-2.36). INTERPRETATION Diabetes is associated with a strong increase in the risk of physical disability. Efforts to promote healthy ageing should account for this risk through prevention and management of diabetes. FUNDING Monash University, Baker IDI Bright Sparks Foundation, Australian Postgraduate Award, VicHealth, National Health and Medical Research Council, Australian Research Council, Victorian Government.

The Duration of Obesity and the Risk of Type-2 Diabetes

OBJECTIVE The evidence for the association between obesity and the risk of type 2 diabetes has been derived mainly from the analysis of the degree of obesity. The role of the duration of obesity as an independent risk has not been fully explored. The objective of the present study was to investigate the association between the duration of obesity and the risk of type 2 diabetes. DESIGN Prospective cohort study. SETTING The Framingham Heart Study (FHS), follow-up from 1948 to 1998. SUBJECTS A total of 1256 FHS participants who were free from type 2 diabetes at baseline, but were obese on at least two consecutive of the studys twenty-four biennial examinations, were included. Type 2 diabetes status was collected throughout the 48 years of follow-up of the study. The relationship between duration of obesity and type 2 diabetes was analysed using time-dependent Cox models, adjusting for a number of covariates. RESULTS The unadjusted hazard ratio (HR) for the risk of type 2 diabetes for men was 1.13 (95 % CI 1.09, 1.17) and for women was 1.12 (95 % CI 1.08, 1.16) per additional 2-year increase in the duration of obesity. Adjustment for sociodemographic variables, family history of diabetes, health behaviour and physical activity made little difference to these HR. For women the evidence of a dose-response relationship was less clear than for men, particularly for women with an older age at obesity onset. CONCLUSIONS The duration of obesity is a relevant risk factor for type 2 diabetes, independent of the degree of BMI.

Projected Progression of the Prevalence of Obesity in Australia

Several country‐specific and global projections of the future obesity prevalence have been conducted. However, these projections are obtained by extrapolating past prevalence of obesity or distributions of body weight. More accurate would be to base estimates on the most recent measures of weight change. Using measures of overweight and obesity incidence from a national, longitudinal study, we estimated the future obesity prevalence in Australian adults. Participants were adults aged ≥25 years in 2000 participating in the Australian Diabetes, Obesity, and Lifestyle (AusDiab) study (baseline 2000, follow‐up 2005). In this population, approximately one‐fifth of those with normal weight or overweight progressed to a higher weight category within 5 years. Between 2000 and 2025, the adult prevalence of normal weight was estimated to decrease from 40.6 to 28.1% and the prevalence of obesity to increase from 20.5 to 33.9%. By the time, those people aged 25–29 in 2000 reach 60–64 years, 22.1% will be normal weight, and 42.4% will be obese. On average, normal‐weight females aged 25–29 years in 2000 will live another 56.2 years: 26.6 years with normal weight, 15.6 years with overweight, and 14.0 years with obesity. Normal‐weight males aged 25–29 years in 2000 will live another 51.5 years: 21.6 years with normal weight, 21.1 years with overweight, and 8.8 years with obesity. If the rates of weight gain observed in the first 5 years of this decade are maintained, our findings suggest that normal‐weight adults will constitute less than a third of the population by 2025, and the obesity prevalence will have increased by 65%.

Comparing trends in BMI and waist circumference

The nature of excess body weight may be changing over time to one of greater central adiposity. The aim of this study is to determine whether BMI and waist circumference (WC) are increasing proportionately among population subgroups and the range of bodyweight, and to examine the public health implications of the findings. Our data are from two cross‐sectional surveys (the US National Health and Nutrition Examination Studies (NHANES) in 1988–1994 (NHANES III) and 2005–2006), from which we have used samples of 15,349 and 4,176 participants aged ≥20 years. Between 1988–1994 and 2005–2006 BMI increased by an average of 1.8 kg/m2 and WC by 4.7 cm (adjusted for sex, age, race‐ethnicity, and education). The increase in WC was more than could be attributed simply to increases in BMI. This independent increase in WC (of on average, 0.9 cm) was consistent across the different BMI categories, sexes, education levels, and race‐ethnicity groups. It occurred in younger but not older age groups. Overall in each BMI category, the prevalence of low‐risk WC decreased and the prevalence of increased‐risk or substantially increased‐risk WC increased. These results suggest that the adverse health consequences associated with obesity may be increasingly underestimated by trends in BMI alone. Since WC is closely linked to adverse cardiovascular outcomes, it is important to know the prevailing trends in both of these parameters.

The decline in coronary heart disease mortality is slowing in young adults (Australia 1976–2006): A time trend analysis

BACKGROUND To examine whether the recent flattening of mortality rates for coronary heart disease (CHD) observed among young adults in the UK and the US is also occurring in the Australian population. METHODS Mortality data from 1976 to 2006 were used to calculate overall age-adjusted and age-specific mortality rates for Australian adults aged ≥ 25 years. Joinpoint regression was fitted to estimate the annual change and detect points in time where significant changes in the trends occur. RESULTS Between 1976 and 2006 age-adjusted CHD mortality rates declined by 73% in men and 70% in women. A steady decline continued in older groups. Beginning in 1991, a slowing of the fall in mortality rates was observed in younger men, and CHD mortality rates were essentially flat in men 25-34 years. Among men aged 35-44, a reduction of the decline in CHD mortality was observed from 1992, and likewise in men aged 45-54 years from 1994. Very similar patterns were observed in women with significant slowdowns starting in 1980, 1988 and 1991 for those aged 25-34 years, 35-44 years and 45-54 years respectively. CONCLUSIONS In Australian men and women aged 25-54 years, the CHD mortality decline has slowed since the early 1990s. The most likely explanations for reduction of the CHD mortality decline are attenuations or reversal of the earlier declines in major traditional risk factors (tobacco smoking, serum cholesterol, blood pressure) and diabetes mellitus.

Epidemiologic Merit of Obese-Years, the Combination of Degree and Duration of Obesity

This study aims to test the effect of combining the degree and the duration of obesity into a single variable-obese-years-and to examine whether obese-years is a better predictor of the risk of diabetes than simply body mass index (BMI) or duration of obesity. Of the original cohort of the Framingham Heart Study, 5,036 participants were followed up every 2 years for up to 48 years (from 1948). The variable, obese-years, was defined by multiplying for each participant the number of BMI units above 30 kg/m(2) by the number of years lived at that BMI. Associations with diabetes were analyzed by using time-dependent Cox proportional hazards regression models adjusted for potential confounders. The incidence of type-2 diabetes increased as the number of obese-years increased, with adjusted hazard ratios of 1.07 (95% confidence interval: 1.06, 1.09) per additional 10 obese-years. The dose-response relation between diabetes incidence and obese-years varied by sex and smoking status. The Akaike Information Criterion was lowest in the model containing obese-years compared with models containing either the degree or duration of obesity alone. A construct of obese-years is strongly associated with risk of diabetes and could be a better indicator of the health risks associated with increasing body weight than BMI or duration of obesity alone.

Projected socioeconomic disparities in the prevalence of obesity among Australian adults

Objective: To project prevalence of normal weight, overweight and obesity by educational attainment, assuming a continuation of the observed individual weight change in the 5‐year follow‐up of the national population survey, the Australian Diabetes, Obesity and Lifestyle study (AusDiab; 2000–2005).

Area-Level Socioeconomic Status and Incidence of Abnormal Glucose Metabolism The Australian Diabetes, Obesity and Lifestyle (AusDiab) study

OBJECTIVE To examine the role of area-level socioeconomic status (SES) on the development of abnormal glucose metabolism (AGM) using national, population-based data. RESEARCH DESIGN AND METHODS The Australian Diabetes, Obesity and Lifestyle (AusDiab) study is a national, population-based, longitudinal study of adults aged ≥25 years. A sample of 4,572 people provided complete baseline (1999 to 2000) and 5-year follow-up (2004 to 2005) data relevant for these analyses. Incident AGM was assessed using fasting plasma glucose and 2-h plasma glucose from oral glucose tolerance tests, and demographic, socioeconomic, and behavioral data were collected by interview and questionnaire. Area SES was defined using the Index of Relative Socioeconomic Disadvantage. Generalized linear mixed models were used to examine the relationship between area SES and incident AGM, with adjustment for covariates and correction for cluster design effects. RESULTS Area SES predicted the development of AGM, after adjustment for age, sex, and individual SES. People living in areas with the most disadvantage were significantly more likely to develop AGM, compared with those living in the least deprived areas (odds ratio 1.53; 95% CI 1.07–2.18). Health behaviors (in particular, physical activity) and central adiposity appeared to partially mediate this relationship. CONCLUSIONS Our findings suggest that characteristics of the physical, social, and economic aspects of local areas influence diabetes risk. Future research should focus on identifying the aspects of local environment that are associated with diabetes risk and how they might be modified.

Co-morbid cardiovascular disease and depression: sequence of disease onset is linked to mental but not physical self-rated health. Results from a cross-sectional, population-based study

PurposeSelf-rated health has been linked to important health and survival outcomes in individuals with co-morbid depression and cardiovascular disease (CVD). It is not clear how the timing of depression onset relative to CVD onset affects this relationship. We aimed to first identify the prevalence of major depressive disorder (MDD) preceding CVD and secondly determine whether sequence of disease onset is associated with mental and physical self-rated health.MethodsThis study utilised cross-sectional, population-based data from 224 respondents of the 2007 Australian National Survey of Mental Health and Wellbeing (NSMHWB). Participants were those diagnosed with MDD and reported ever having a heart/circulatory condition over their lifetime. Age of onset was reported for each condition. Logistic regression was used to explore differences in self-rated mental and physical health for those reporting pre-cardiac and post-cardiac depression.ResultsThe proportion of individuals in whom MDD preceded CVD was 80.36% (CI: 72.57–88.15). One-fifth (19.64%, CI: 11.85–27.42) reported MDD onset at the time of, or following, CVD. After controlling for covariates, the final model demonstrated that those reporting post-cardiac depression were significantly less likely to report poor self-rated mental health (OR:0.36, CI: 0.14–0.93) than those with pre-existing depression. No significant differences were found in self-rated physical health between groups (OR:0.90 CI: 0.38–2.14).ConclusionsMDD is most common prior to the onset of CVD. Further, there is an association between pre-morbid MDD and poorer self-rated mental health. To our knowledge, this is the first time this has been demonstrated in a national, population-based survey. As self-rated health has been shown to predict important outcomes such as survival, we recommend that those with MDD be identified as vulnerable to CVD onset and poorer health outcomes.