Novel Predictors of Age-Related Changes in Lung Function

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Smoking and air pollution exposure are modifiable predictors of age-related declines in lung function. There is some evidence to suggest that physical inactivity may be a predictor of age-related changes in lung function; however, the independent contribution of sitting time, physical activity, and cardiorespiratory fitness have not been investigated to date.

PURPOSE: To determine the association between age-related declines in lung function with sitting time, physical activity and cardiorespiratory fitness in a population of healthy adults.

METHODS: Data from the Fels Longitudinal Study (1999-2015) were used for analysis (n=996), with serial data available for up to five study visits. Forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were measured using a metabolic cart (SensorMedics VMax). Physical activity was measured using the Baecke questionnaire and TV time was self-reported as either never, seldom, sometimes, often, and very often. Cardiorespiratory fitness was determined by calculating VO2max from a submaximal treadmill test. Data were analyzed using repeated measures hierarchical linear models in SAS.

RESULTS: The sample was middle-aged (45.0 ±17 years), overweight (BMI: 27.1 ± 5.6 kg/m2), and their VO2max was 36.6±9.8 ml/kg/min. Approximately 53% of the sample reported watching TV often and only 3% of the sample reported engaging in regular physical activity often. In models adjusted for age, BMI, physical functioning and smoking status, there was a significant TV time x sex interaction (p<0.0001) when modeling FEV1, such that higher TV time in females was associated with worse FEV1 compared to males. A physical activity x sex interaction (p<0.0001) was also observed in adjusted models of FEV1. When TV time, physical activity and cardiorespiratory fitness were included in the same model, only the association between cardiorespiratory fitness and FEV1 remained significant (p<0.001).

CONCLUSION: Cardiorespiratory fitness is a predictor of age-related changes in lung function. Among deconditioned adults, particularly in females, reducing sedentary time and increasing physical activity may lead to an increase in cardiorespiratory fitness and thus may attenuate the age-related decline in lung function.