The Association between Body Mass Index and Mortality among the Oldest Old in China

The study is to examine the association between BMI and all-cause mortality in the oldest old (≥80 years). The study used a large sample sized prospective cohort study design. Chinese Longitudinal Healthy Longevity Survey (CLHLS) is a dataset between 2008 and 2014. Population: 8026 participants aged 80 years and older were followed every two to three years. Body weight and height were measured. BMI was calculated based on weight, height using a validated equation. Deaths were ascertained from family members during follow-up. Compared with lower weight, higher BMI was associated with a lower mortality risk (HRs: 1.20 (95%CI 1.13-1.27) but overweight (HR 0.89 (95%CI 0.81-0.99)) were associated with a lower risk. Obesity had a HR 0.91 (95%CI 0.78-1.05) for mortality. Among oldest old Chinese, higher BMI is associated with an increased risk of all-cause mortality but further study of the association is still needed.