Abstract
OBJECTIVE: Chronic bronchitis and emphysema (CBE) are two main types of chronic obstructive pulmonary disease (COPD). We aimed to investigate the relationship between dietary calcium intake and the risk of CBE. METHODS: Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 2007-2012. The ratio of forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) < 0.7 was used to define airflow obstruction. Multivariate logistic regression was performed to assess the effects of dietary calcium intake on CBE and airflow obstruction. Dietary calcium intake was divided into quartiles, with the lowest quartile set as the reference group. Linear regression models were applied to explore the association between dietary calcium intake and lung function. RESULTS: A total of 10,143 participants were enrolled in the study, including 594 CBE and 9549 non-CBE individuals. The average dietary calcium intake was 908.5 ± 636.1 mg/day in the CBE group and 951.9 ± 599.7 mg/day in the non-CBE group. When using the lowest quartile of dietary calcium intake as a reference, the second, third, and fourth quartiles reduced the risk of CBE by 0.803 [95% confidence interval (CI): 0.802-0.804; P < 0.001], 0.659 (95% CI: 0.659-0.660; P < 0.001) and 0.644 (95% CI: 0.643-0.644; P < 0.001) times, respectively. Increased dietary calcium intake was correlated with reduced risk of airflow obstruction. Dietary calcium intake positively predicts FEV1 (β = 0.225, P < 0.001) and FVC (β = 0.232, P < 0.001). CONCLUSION: Increased intake of dietary calcium may contribute to higher lung function, a lower risk of CBE and airflow obstruction. Since the cross-sectional design makes it difficult to determine a causal relationship, further research is needed to confirm these findings and explore the underlying mechanisms.