Effects of replacing sitting time with physical activity on lung function: An analysis of the Canadian Longitudinal Study on Aging

Background: Sitting time and physical activity may be modifiable determinants of lung function. The purpose of this study was to assess the effect that replacing various movement behaviours has on lung function among individuals with and without obstructive lung disease. Data and methods: For analysis, data were used from participants of the Canadian Longitudinal Study on Aging, recruited between 2012 and 2015. Lung function was assessed using spirometry. A modified version of the Physical Activity Scale for the Elderly was used to assess sitting time and physical activity levels. Isotemporal substitution analysis was performed to analyze the effects of replacing 30 minutes per day of one movement behaviour with another, keeping the total time constant. Analyses were run separately for individuals with an obstructive lung disease (asthma, chronic obstructive pulmonary disease, or forced expiratory volume in 1 second [FEV ₁ ] < 5th percentile lower limit of normal; n=3,398), and healthy adults (n=14,707). Results: When sitting time was replaced with 30 minutes per day of any type of physical activity or sleep, an increase in percent (%) of predicted FEV ₁ (i.e., β=0.65, confidence interval [CI]: 0.43, 0.88 for replacing sitting time with strenuous or strengthening activity) was observed among healthy adults. Among adults with obstructive lung disease, replacing 30 minutes per day of sitting time or sleep duration with strenuous or strengthening activity was associated with an improvement in the percent of predicted FEV ₁ (i.e., β=0.98, CI: 0.13, 1.82 for replacing sleep duration with strenuous or strengthening activity). Interpretation: Replacing sitting time with physical activity leads to significant improvements in lung function among adults with an obstructive lung disease, as well as among adults without a respiratory disease.