Influence of self-reported socio-economic status on lung function of adult Nigerians.

Objectives: Low socio-economic status is known to be associated with reduced lung function in childhood and early adulthood, and an increased risk of cardiovascular disease in older adults. The lung function of people in developing nations is known to be lower than that of their counterparts in developed nations. This study assessed whether childhood socio-economic status is related to lung function in adults in Nigeria.

Design: Cross-sectional study.

Setting: Ife central local government, Ile-Ife, Nigeria.

Participants: One thousand nine hundred and thirty healthy adults aged 40 to 80 years took part in the study. Forced vital capacity (FVC) and forced expiratory volume in 1second (FEV(1)) were measured with a spirometer, and peak expiratory flow (PEF) was measured with a mechanical peak expiratory flow meter. The socio-economic status questionnaire gave equal importance to education, occupation and family income. Based on the score, the subjects were classified as lower, middle or higher status.

Main Outcome Measures: Spirometry, assessment of peak flow meter and questionnaire to assess socio-economic status.

Results: The results showed a difference between the group with the highest socio-economic status and the other two groups [mean (standard deviation) FVC: high 3.63l (0.33), middle 3.57l (0.41), low 3.38l (0.35)]. The mean difference between the high and middle socio-economic groups was 0.07l [95% confidence interval (CI) 0.02 to 0.11]. A similar difference existed for FEV(1): high 3.16l (0.28), middle 3.06l (0.31), low 2.94l (0.34). The mean difference between the high and middle socio-economic groups was 0.11l (95% CI 0.07 to 0.15). Values for PEF were: high 404.30l/second (35.98), medium 390.56l/second (41.53), low 376.03l/second (45.81). The mean difference between the high and medium socio-economic groups was 13.74l/second (95% CI 8.42 to 19.06). There was a weak but significant association between socio-economic status and FVC (r=0.28), FEV(1) (r=0.26) and PEF (r=0.25).

Conclusion: Self-reported low socio-economic status is associated with lower lung function among adult Nigerians. This may increase their risk for respiratory and cardiovascular disease.