Longitudinal study of the influence of obesity, C-reactive protein, and smoking on FEV1 decline in young adulthood.

Background: Chronic obstructive pulmonary disease (COPD) is a disease with a high socioeconomic burden for the global population. Identifying those individuals with a higher potential to develop the disease is essential for reducing its incidence.

Methods: This is an observational, longitudinal study that uses data from the 1978/1979 Ribeirão Preto City birth cohort (São Paulo State, Brazil). The study included 895 individuals who participated at the age of 23-25 and 37-38 years. Asthmatics were diagnosed by methacholine bronchial challenge test and were excluded from the analysis. A multiple linear regression was performed to evaluate the association of active smoking, passive smoking, body mass index (BMI), C-reactive protein (CRP) levels, and respiratory symptoms with FEV1 variation between ages.

Results: The analysis showed an association between BMI, CRP levels, and active smoking with FEV1 fall. Active smoking increased FEV1 decline by 1.95%. For each 1 kg/m² increase in BMI, there was a 0.28% loss in FEV1, while an increase in CRP level of 1 mg/dL was associated to a 0.76% additional FEV1 decline.

Conclusion: In addition to the well-known relationship between smoking and pulmonary function decline, there was also an association with BMI and CRP levels, suggesting the hypothesis that a metabolic process may contribute to the development of COPD.