Fruit and fish consumption: a possible explanation for population differences in COPD mortality (The Seven Countries Study).

Objective: To investigate whether average intake of antioxidants, fruits, vegetables and fish may help to explain international differences in chronic obstructive pulmonary disease (COPD) mortality.
Design: Ecological analysis using information on baseline diet and the 25-year COPD mortality rate in the 16 cohorts of the Seven Countries Study.
Setting: Population-based cohorts.
Subjects: Men aged 40-59 years at baseline.
Methods: Dietary information was collected at baseline in small random samples of each cohort. In 1987 the reported foods were bought locally and analysed chemically. After 25 years of follow-up the underlying cause of death of those who died was established centrally. COPD mortality rate ratios were calculated, for a change equivalent to 10% of the overall mean consumption of a dietary factor.
Results: We observed independent inverse associations between 25-year COPD mortality and baseline consumption of fruits (rate ratio 0.49; 95% confidence interval 0.36-0.67) and fish (rate ratio, 0.97; 95% confidence interval 0.93-1.00), after adjustment for potential confounders. COPD mortality showed no statistically significant association with intake of antioxidants or vegetables. Fruit and fish consumption together explained about 67% of the variance in the COPD mortality rates of the cohorts.
Conclusions: Fruit and fish consumption may partly explain population differences in COPD mortality. This is in accordance with suggestions for a relationship between fruit and fish consumption and COPD observed in studies in individuals.