Lung function in older humans: the contribution of body composition, physical activity and smoking.

An allometric model was used to determine the important factors related to the decline in forced expiratory volume (FEV1.0) across ages 55-86 years in independently living men and women. Measurements were available from a randomized sample of 181 men and 203 women residing in London, Ontario, Canada. The effects of height, age, sex, adiposity, fat free mass (FFM), grip strength and physical activity (PA) on FEV1.0 were assessed using an allometric model to test the hypothesis that sex differences in lung function would be due in part to sex-related differences in the aforementioned variables and would therefore be eliminated by our analysis. The following model was linearized and parameters were identified using standard multiple regression: FEV1.0 = height(beta1) x FFM(beta2) x grip strength(beta3) x PA(beta4) x exp(beta0 + beta5age + beta6sex + beta7smoking + beta8%body fat) x epsilon. Results indicate that the amount of FFM and heavy intensity physical activity participated in by the elderly may be more important in influencing forced expiratory function than previously recognized. In addition, results from this study have confirmed the importance of age and height in the prediction of FEV1.0 and demonstrated a negative effect of smoking on lung function. Individuals with a greater FFM and physical activity level tended to be associated with an above average lung function performance. The cross-sectional rate of decline in FEV1.0 determined from our model was approximately 12% per decade.