Accelerometer-based physical activity in daily life is not positively associated with better pulmonary function in adult smokers without airflow obstruction

Background: Epidemiological studies suggest that an appropriate level of physical activity in daily life (PADL) may reduce the rate of decline in pulmonary function regardless of smoking. However, studies evaluating this relationship were based on physical activity questionnaires, which have limitations in accurately quantifying the amount and intensity of PADL. Accelerometer-based studies are scarce or nonexistent in adult smokers. We hypothesized that smokers with appropriate accelerometer-based PADL may present better pulmonary function regardless of their smoking history.

Purpose: The aim of this study was to evaluate the association between accelerometer-based PADL and pulmonary function in adult smokers without airflow obstruction.

Methods: Sixty-three adult smokers from the Epidemiological Study on Human Movement and Hypokinetic Diseases (EPIMOV Study) were enrolled (51 ± 10 yr). After obtaining clinical, demographic and anthropometric data, participants underwent spirometry with measures of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1) and FEV1/FVC ratio. Physical activities at home, at leisure, during transportation and at work were assessed using the international physical activity questionnaire (IPAQ). Physical activity in daily life was also measured by means of 7 days of monitoring using a triaxial accelerometer (Actigraph, GT3x+). Physical inactivity was defined as less than 150 min/wk of moderate to vigorous physical activity. The cardiovascular risk assessment was completed recording factors such as hypertension, diabetes, dyslipidemia, and obesity. The self-reported smoking load was quantified in pack-yr. We assessed bivariate associations between indices of pulmonary function and accelerometer-based PADL and multivariate regression models were developed using percentage of predicted values of FVC and FEV1 as the main outcomes. These models were adjusted for smoking load, PADL, and cardiovascular risk factors.

Results: The mean smoking load of the participants was 24 ± 22 pack-yr. We observed moderate but significant correlations between FVC and FEV1 and some indices of PADL, with a range r = 0.29 to r = 0.42. Interesting, we observed significant correlations between FVC and FEV1 and only the amount of vigorous PADL (r = 0.30). However, there were no significant differences between physically active and inactive participants regarding the pulmonary function indices. After multivariate regression analysis, only smoking load and hypertension were selected as significant predictors of VEF1 (R2 = 0.225) and smoking load and diabetes for FVC (R2 = 0.246). We observed no significant associations between pulmonary function and PADL or the amount of vigorous PADL after regression analysis.

Conclusions: We may conclude that an appropriate PADL, even considering the week hours spent in vigorous physical activity, was not associated with better pulmonary function in adult smokers without airflow obstruction. Our results suggest that pulmonary function is strongly associated to increased cardiovascular risk. Pulmonary monitoring could be useful to more accurately predict cardiovascular risk and appropriate levels of PADL seems to be insufficient to prevent smoking-related pulmonary function deterioration.

Implications: A physically active lifestyle may not be enough to reduce the deleterious effects of smoking on pulmonary function. Cardiovascular risk monitoring might be more important for preventing pulmonary function decline and this issue should be further assessed in cohort studies.