Longitudinal Association Between Diet Quality and Asthma Symptoms in Early Adult Life in a Brazilian Birth Cohort

BACKGROUND: The role of diet in the etiology of asthma is still inconclusive. This paper evaluated the longitudinal association between diet quality and chest wheezing in young adults. METHODS: This is a longitudinal study with follow-up information from 18- and 22-year-olds (18y and 22y) of the 1993 Pelotas (Brazil) Birth Cohort. Chest wheezing occurrence and number of events in the last year were reported at 22y. Diet quality was measured with a revised version of the Healthy Eating Index (IQD-R) for the Brazilian population at 18y and 22y by food frequency questionnaire referring to the last 12 months. The diet quality continuity was classified as good (always 1st IQD-R tertile), intermediate (always 2nd tertile/change tertile) and poor (always 3rd tertile). RESULTS: A total of 2986 young individuals were evaluated; 51.4% were female. Prevalence of wheezing at 22y was 10.1% (95% CI: 9.1–11.2), and of these patients, 10% reported at least one event in the past year. Better IQD-R score, both at 18y and at 22y, the lower the odds of wheezing in the past year. Regarding the diet quality continuity from 18y to 22y, staying on a poor diet increased by more than three-fold the odds of chest wheezing (OR=3.28; 95% CI: 1.84–5.84) and of wheezing events (OR=3.32; 95% CI: 1.89–5.85) compared to staying on a good diet, after adjustment for confounding variables. CONCLUSION: The overall quality of the diet seems to be more important than the individual components in the effect on asthma symptoms. Low-quality diet persistence increased the odds of chest wheezing and the number of events.