Body Mass Index (BMI), BMI change and mortality in community-dwelling seniors without dementia

Abstract

Recently Canada adopted the World Health Organization's (WHO)Weight Classification system for Body Mass Index (BMI). To date, there has been minimal investigation on the predictive ability of BMI on mortality in seniors. This study investigates the predictive ability of the BMI categories identified in this Weight Classification System and change in BMI on mortality in Canadian seniors.

Methods: Canadian Study of Health and Aging (CSHA) participants who completed clinical examination (including body weight measurements) in 1991 (CSHA1) and 1996 (CSHA2) were included (n = 539). BMI change (CSHA1 to CSHA2) was categorized as no change/mild increase (0 to < 2.0 units), mild decrease (-0.1 to < -2.0 units), or significant increase/decrease (> or = +/-2.0 units). The outcome was subsequent 5-year-mortality, i.e. death between CSHA2 and CSHA3 (2001). Logistic regression controlled for age, gender, education level, marital status, smoking and cognitive status.

Results: BMI at CSHA1 was not a significant predictor of all-cause mortality between CSHA2 and CSHA3. A significant decrease in BMI regardless of BMI category predicted death (OR 2.10 95% CI 1.17, 3.80). Other factors predictive of death were age and cognitive impairment without dementia.

Conclusion: A static measure of BMI is a less useful measure of mortality risk than weight change in older adults. Weight change, especially weight loss resulting in a BMI change of at least 2.0 units, is predictive of mortality and should be considered a warning sign.