| Summary: | <p>Background: Understanding the relationship between body-mass index (BMI) and vascular disease at older age has become increasingly important in the many countries where both average age and BMI are rising.</p><p> Methods: In this prospective cohort study, 12 203 men aged ≥65 years were recruited in 1996-99 from the general population in Perth, Western Australia. BMI was calculated from height and weight measured at recruitment. To limit the effect of reverse causality, analyses were restricted to men without prior vascular disease and excluded the first four years of follow-up. During a mean follow-up of a further 8 (SD 3) years, there were 1136 first major vascular events. Cox regression models (adjusted for age, education and smoking) related BMI at recruitment to incidence of major vascular events (first-ever myocardial infarction, first-ever stroke or death from any vascular cause). </p><p> Results: The mean BMI at recruitment was 26.7 (SD 4) kg/m2. At ages 65-94 years (mean age at event 81 years), the lowest risk of major vascular events was at about BMI 22.5-25 kg/m2. In the higher BMI range (≥25 kg/m2), 5 kg/m2 higher BMI was associated with 33% higher risk of major vascular events (hazard ratio [HR] 1.33 [95% CI: 1.18-1.49]): 24% higher risk of ischaemic heart disease (1.24 [1.06-1.46]); 34% higher risk of stroke (1.34 [1.11-1.63]); and 78% higher risk of other vascular death (1.78 [1.32-2.41]). In the lower BMI range (<25 kg/m2), there was not strong evidence of an association with major vascular events overall (HR per 5 kg/m2 higher BMI 0.82 [95% CI 0.61-1.12]).</p><p> Conclusions: In this population of older men, risk of major vascular events was lowest at about BMI 22.5-25 kg/m2. Above this range, BMI was strongly related to incidence of major vascular events, with each 5 kg/m2 higher BMI associated with about 30% higher risk.</p>
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