Objective: To investigate the relationship between mortality and BMI in older people, taking into account other established mortality risk factors.
Methods: A total of 3,646 French community dwellers aged 65 years and older from PAQUID cohort study were included. Cox proportional-hazards analysis was used to assess association between BMI and mortality.
Results: Death occurred in 54.1% of the cohort more than 13 years: 68.99% of the underweight (BMI <19), 52.13% of the obese (BMI >30), 51.66% of the overweight (BMI 25-30), and 51.79% of the reference participants (BMI 22-25) died.The relative risk of death as a function of BMI, adjusted for gender and age, formed a U-shaped pattern, with larger risks associated with lower BMI (<22.0) and for BMI of 25.0 to 30.0 and BMI >/=30. (BMI 22.0-24.9 was the reference.) After adjustment for demographic factors, smoking history, and comorbidity, increased mortality risk persisted in underweight older people, BMI <18.5 and BMI 18.5-22 (respectively, HR = 1.45, 95% CI 1.17-1.78; HR = 1.27, 95% CI 1.12-1.43) compared with reference. Overweight (BMI 25-29.9) and obesity (>/=30) were not associated with increased mortality compared with the reference category (respectively, HR = 0.98, 95% IC 0.88-1.10; HR = 1.06, 95% IC 0.89-1.27). Similar relationships persisted for disabled participant. For nondisabled participant disability did not alter the associations for BMI of 25.0 and higher but for BMI less than 22.0, the risks become insignificantly different from those for the reference group.
Discussion: BMI below 22 kg/ m(2) is a risk factor for 13-year mortality in older people, but our findings suggest that overweight and obesity may not be associated to mortality after adjustment for established mortality risk factors.