Lung function across the life course in Kenya: a series of cross-sectional surveys

Background The high prevalence of COPD in sub-Saharan Africa is poorly understood. In high income countries, COPD is the consequence of sub-optimal lung growth during childhood and/or accelerated lung function decline in adult life. We have conducted cross-sectional studies to measure the lung function of children and adults in Kenya and to identify associations with age. Methods We performed spirometry in three groups in Kenya: a random sample of schoolchildren in two districts of urban Nairobi and age/sex stratified representative community samples of adults in Nairobi and rural Machakos. Forced expiratory volume in 1 s (FEV 1 ) and forced vital capacity (FVC) were expressed as z-scores using race-neutral GLI-Global reference equations. Results The mean (95% CI) FEV 1 z-score in Nairobi schoolchildren [n=2373, median age 10 years (IQR 8,13) 52% girls] was −0.60 (−0.64, −0.55); in Nairobi adults [n=2936, median age 32 years (24,43), 62% female] −0.49 (−0.53, −0.45); and in Machakos adults [n=1607, median age 46 (35,59), 65% female] −0.67, (−0.72, −0.61). In adults, FEV 1 was negatively associated with age (FEV 1 z-score regression coefficient β −0.005/year (95% CI −0.009, −0.002) p=0.005, and there was a negative interaction between residence in Nairobi and age, β −0.006/year (95% CI −0.011, −0.001), p=0.020. Conclusion The lung function of children and adults in Kenya was lower than predicted by race-neutral GLI-Global reference equations and in adults, lung function was negatively associated with age with this negative association being greater in urban Nairobi than in rural Machakos. Further work is required to identify and mitigate relevant influences.