Objective To study the relationship between body mass index (BMI) and mortality among 75-year-olds with and without diabetes mellitus type 2 (DM) or impaired fasting glucose (IFG).
Design Prospective population-based cohort study with a 10-year follow-up.
Participants A random sample of 618 of the 1100 inhabitants born in 1922 and living in the city of Västerås in 1997 were invited to participate in a cardiovascular health survey; 70% of those invited agreed to participate (432 individuals: 210 men, 222 women).
Outcome measures All-cause and cardiovascular mortality.
Results 163 of 432 (38%) participants died during the 10-year follow-up period. The prevalence of DM or IFG was 41% (35% among survivors, 48% among non-survivors). The prevalence of obesity/overweight/normal weight/underweight according to WHO definitions was 12/45/42/1% (14/43/42/1% among survivors, 9/47/42/2% among non-survivors). The hazard rate for death decreased by 10% for every kg/m2 increase in BMI in individuals with DM/IFG (HR 0.91, 95% CI 0.86 to 0.97; p=0.003). After adjustment for sex, current smoking, diagnosed hypertension, diagnosed angina pectoris, previous myocardial infarction and previous stroke/transient ischaemic attack, the corresponding decrease in mortality was 9% (HR 0.92, 95% CI 0.86 to 0.99; p=0.017). These findings remained after exclusion of individuals with BMI<20 or those who died within 2-year follow-up. In individuals without DM/IFG, BMI had no effect on mortality (HR 1.01, 95% CI 0.95 to 1.07; p=0.811). The HR for BMI differed significantly between individuals with and without DM/IFG (p interaction=0.025). The increased all-cause mortality in individuals with DM/IFG in combination with lower BMI was driven by cardiovascular death.
Conclusion High all-cause and cardiovascular mortality was associated with lower BMI in 75-year-olds with DM/IFG but not in those without DM/IFG. Further studies on the combined effect of obesity/overweight and DM/IFG are needed in order to assess the appropriateness of current guideline recommendations for weight reduction in older people with DM/IFG.
- cardiovascular diseases
- fasting glucose
- obesity paradox
- BMJ open
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To cite: Nilsson G, Hedberg P, Öhrvik J. Survival of the fattest: unexpected findings about hyperglycaemia and obesity in a population based study of 75-year-olds. BMJ Open 2011;1:e000012. doi:10.1136/bmjopen-2010-000012
Funding The original cardiovascular health survey was supported by grants from SparbanksstiftelsenNya and Västmanland's Research Foundation Against Cardiovascular Diseases. The authors are independent from the funders of the original study.
Competing interests None.
Ethics approval The study was approved by the research ethics committee of Uppsala University, Sweden.
Contributors GN and JO conceived and designed the study, performed the data analyses and interpreted the results. GN wrote the first draft of the manuscript. PH contributed to the initial collection of the data and verified the medical diagnoses. All authors critically reviewed the manuscript for important intellectual content and approved the final version of the paper. JO acts as guarantor of the paper.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Statistical code and datasets are available from the corresponding author at .
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