Flavonoid intakes inversely associate with chronic obstructive pulmonary disease in smokers

INTRODUCTION: Higher flavonoid intakes are beneficially associated with pulmonary function parameters, however, their association with chronic obstructive pulmonary disease (COPD) is unknown. This study aimed to examine associations between intakes of 1) total flavonoids, 2) flavonoid subclasses, and 3) major flavonoid compounds and incident COPD in participants from the Danish Diet, Cancer, and Health study.

METHODS: This prospective cohort included 55,413 males and females without COPD, aged 50-65 years at recruitment. Habitual flavonoid intakes at baseline were estimated from a food frequency questionnaire using Phenol-Explorer. Danish nationwide registers were used to identify incident cases of COPD. Associations were modelled using restricted cubic splines within Cox proportional hazards models.

RESULTS: During 23 years follow-up, 5557 participants were diagnosed with COPD. Of these, 4013 were current-, 1062 were former-, and 482 were never-smokers. After multivariable adjustments, participants with the highest, compared to the lowest, total flavonoid intakes had a 20% lower risk of COPD [Quintile 5 versus Quintile 1 HR (95% CI): 0.80 (0.74, 0.87)]; a 6-22% lower risk was observed for each flavonoid subclass. The inverse association between total flavonoid intake and COPD was present in both males and females but was only present in current [HR: 0.77 (0.70, 0.84)] and former [HR: 0.82 (0.69, 0.97)], but not never, smokers. Furthermore, higher flavonoid intakes appeared to lessen, but not negate, the higher risk of COPD associated with smoking intensity.

CONCLUSION: Dietary flavonoids may be important for partially mitigating the risk of smoking-related COPD. However, smoking cessation should remain highest priority.