The synergy of low lung function and low body mass index predicting all-cause mortality among older Japanese-American men.

Objective: To assess the joint characteristics of low standardized weight and compromised pulmonary function in predicting all-cause mortality.
Design: A population-based, prospective cohort study.
Setting: Oahu Island, Hawaii.
Participants: Surviving Japanese-American men of the Honolulu Heart Program cohort, 71 to 93 years of age (N = 3059).
Measurements: Body mass index (BMI-weight in kilograms/square of height in meters) and 1-second forced expiratory volume (FEV1) as a percentage of age- and height-predicted FEV1 from the 1991 to 1993 examination of the cohort. Mortality data derived from the ongoing tracking of deaths of the cohort. Relations of selected risk factors among joint levels of BMI (< or = 21, > 21 to < 25, > or = 25 kg/m2) and percent predicted FEV1 (< or = 70%, > 70%) were determined. The impact of these covariates on relations between joint BMI/percent predicted FEV1 levels and subsequent all-cause mortality was assessed.
Results: The highest age-adjusted mortality rate (91.9 deaths per 1000 person-years) was noted among men characterized by the joint conditions of percent predicted FEV1 < or = 70% and BMI < or = 21 kg/m2. This rate was 4.0 times the mortality rate of a "healthy" reference group characterized by percent predicted FEV1 > 70% and 21 < BMI < 25 kg/m2. This rate ratio is attenuated to 3.2 upon statistical control for measures of current and past smoking behavior. Among the three strata of BMI, statistical interaction is reflected in a heterogeneity of mortality rate differences (49.7, 21.8, -9.6 deaths/person-year, respectively) and rate ratios (2.18, 1.98, .66, respectively) comparing men with percent predicted FEV1 < or = 70% to > 70%.
Conclusion: Joint loss of pulmonary function and relative weight is predictive of subsequent all-cause mortality in excess of additive or multiplicative effects of each condition separately. Smoking behavior may contribute to this observation.