The relationship between fish intake and the prevalence of asthma: the Tokorozawa childhood asthma and pollinosis study

Objective: The Japanese have a higher intake of fish and a lower incidence of asthma than occupants of western countries. The present epidemiological study investigated the relationship between dietary fish intake and the prevalence of asthma among a childhood population.

Methods: Subjects represented all public elementary and junior high schools in Tokorozawa City in Japan (age range: 6-15 years old). The study population included 1,673 currently asthmatic students and 22,109 controls. Participants' parents completed the Japanese version of American Thoracic Society and Division of Lung Diseases, National Heart, Lung, and Blood Institute questionnaire for children, adopted by the Japan Environment Agency. We added supplementary questions (e.g., parental history of asthma and questions about frequency of foods eaten, including frequency of fish intake). Odds ratios for cases of current asthma according to frequency of fish intake were calculated, and a logistic regression analysis was used to adjust for possible confounding variables.

Results: After adjustments for age, gender, parental history of asthma, and vegetables and fruits intake, a significantly higher prevalence of asthma was noted among subjects who ate fish one to two times a week than among those who ate fish one to two times a month (adjusted odds ratio: 1.117; 95% confidence interval: 1.005-1.241; P = 0.041). The risk increased gradually with increasing frequency of fish intake, and the positive trend was statistically significant.

Conclusions: The results indicated that frequency of fish intake was positively related to the prevalence of asthma. This result might have important implications for health.