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 (FEV 1) and forced vital capacity 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 years (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 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.