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 suboptimal 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 (FEV1) and forced vital capacity were expressed as z-scores using race-neutral GLI-Global reference equations. Results The mean (95% CI) FEV1 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 years (35–59), 65% female) −0.67 (−0.72– −0.61). In adults, FEV1 was negatively associated with age (FEV1 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 Global Lung Function Initiative (GLI)-Global reference equations. In adults, a negative association between lung function and age was greater in urban, than in rural, settings. Further work is required to identify and mitigate relevant influences.