The relationship between body composition, physical activity and dynamic lung volume variables in a rural and an urban South African community: the PURE study
The high prevalence of respiratory diseases among South Africans poses a significant challenge to the human and medical resources, as well as the economic sector due to related morbidity and mortality. Poor pulmonary function (PF) is associated with higher respiratory disease prevalence and poor prognosis. Body composition and physical activity (PA) have mechanical and inflammatory effects influencing respiration. Poor body composition, defined by excessive fat mass (FM) and low lean body mass (LBM), can limit chest expansion. Physical inactivity promotes pro-inflammatory conditions and thus airway narrowing. Both poor body composition and physical inactivity adversely affects dynamic lung volume variables such as forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁). This study investigated the relationship between body composition, PA and dynamic lung volume variables in a rural and an urban South African community. A cross-sectional study design was followed among 476 participants from the South African subset of the Population Rural Urban Epidemiology (PURE) study. Body composition was determined by anthropometric measurements (body mass, height, waist, and hip circumference and triceps and subscapular skinfolds). Subsequently body mass index (BMI), Waist-to-Hip Ratio (WHR) and Waist-to-Height Ratio (WHtR) were calculated. Physical activity data were obtained subjectively by means of the International Physical Activity Questionnaire (IPAQ) short version. Pulmonary function was measured objectively by means of spirometry providing dynamic lung volume variables, FVC, FEV₁, FVC/FEV₁ and Peak Expiratory Flow (PEF). Results indicated a tendency of participants to be overweight (mean BMI = 26.83kg/m²) despite exceeding the American College of Sports Medicine’s PA recommendations for healthy persons by spending an average of 277 minutes/week in moderate intensity PA. Following spirometry 85.9% of participants demonstrated with normal, 7.4% with obstructive and 6.7% with restrictive patterns as defined by the Global initiative for chronic Obstructive Lung Disease (GOLD). The rural and urban community differed significantly with regards to age (t = 2.695, p = 0.007), smoking status (t = -2.955; p = 0.003), triceps skinfold (t = -5.671; p < 0.001), moderate intensity physical activity minutes/week (t = 2.941; p = 0.003), sitting time (t = 3.838; p < 0.001), prevalence of obstructive spirometry ( t = -1.349; p = 0.007), absolute FVC (t = -2.372; p = 0.018), absolute FEV₁ (t = -2.781; p = 0.006), forced expiratory time (t = - 4.616; p < 0.001) and quality of spirometry testing (t = 2.174; p = 0.030). During partial correlation, height demonstrated statistically significant associations with FVC (r = 0.307; p < 0.001), FEV₁ (r = 0.240; p < 0.001) and PEF (r = 0.154; p = 0.001). Adiposity was negatively associated with dynamic lung volume variables reaching statistical significance between FVC/FEV₁ and triceps skinfold (r = -0.134; p = 0.046) in the rural community. Consequently, body composition variables significantly predicted the change in FVC (R² = 0.418; p < 0.001), FEV₁ (R² = 0.325; p < 0.001) and PEF (R² = 0.159; p = 0.002). The association between most PA parameters and PF did not reach statistical significance. Walking, however, had a beneficial effect on PF with positive associations for FVC (r = 0.094; p = 0.049) and FEV₁ (r = 0.149; p = 0.034) in the study population. It can be concluded that both body composition and PA has an influence on PF in a rural and an urban South African sample. While body composition showed statistically significant associations with dynamic lung volume variables, more research is required with regards to PA as walking was the only PA variable reaching statistical significance with FVC and FEV₁. Primary and secondary prevention and treatment programs should, therefore, emphasise a healthy body composition and explore the utilization of PA.
- Health Sciences