The relationship between different diet quality indices and severity of airflow obstruction among COPD patients

Background: Chronic obstructive pulmonary disease (COPD) is a major public health problem worldwide. Smoking is the number one cause of COPD; however, genetic, environmental and dietary factors contribute to the etiology of this disease. In this study, we assessed the association between three diet quality indices -the Healthy Eating Index-2005 (HEI-2005), the Healthy Eating Index-2010 (HEI-2010), and Mediterranean Diet Score (MED)- and the severity of disease in COPD patients.   Methods: This cross-sectional study was performed at  Rasul-e-Akram Hospital in Tehran on 121 COPD patients with the mean age of (SD) of 66.1(10.9) years. A pulmonary specialist diagnosed all participants based on a spirometry test. They were categorized into four groups (1, 2, 3, 4 stages of disease). Three diet quality indices, spirometry test and determination of disease severity were performed for all the participants. ANCOVA and Kruskal-Wallis test were used to assess the relationship between dietary quality indices and severity of the disease. The relationship between HEI-2010, HEI-2005, MED score, their components and lung function was assessed using a multiple linear regression analysis. All analyses were done using SPSS 18.   Results: Reduction of the Healthy Eating Index-2010 and MED score were observed along with the increase in disease severity, but they were not significant. The relationship between the three diet quality indices and lung function showed a significant association between MED score and Forced expiratory volume in one second (FEV1), The Forced Vital Capacity (FVC) (β=2.9, 95% CI (1.1, 4.8), p=0.002), (β=2.8, 95% CI (0.9, 4.8), p=0.007), respectively.   Conclusion: Mediterranean dietary pattern and obtaining a better score on HEI-2010 diet were associated with a better lung function test.