Dietary patterns and asthma incidence in adult population. Systematic review and meta-analysis

We conducted a systematic review and meta-analysis of published prospective cohort studies and randomized controlled trials (RCT) assessing the association between a healthy dietary pattern and adult-onset asthma following the PRISMA and MOOSE guidelines.

Inclusion criteria were RCT or cohort studies evaluating a dietary pattern and their association with asthma incidence in adults. We searched two databases, Medline (PubMed) and ISI Web of Science until November 2023. Two independent reviewers assessed the quality of the included studies. Risk of bias was assessed using the Newcastle-Ottawa Scale (NOS).

Ten cohort studies were included in the systematic review and seven of them were assessed in a quantitative random-effects meta-analysis. They included a total of 597,909 participants with 10,988 asthma events. Dietary patterns or indexes were most frequently measured with validated food frequency questionnaires. Follow-up ranged between 5 and 16 years. When we pooled all the included studies, no significant reduction in asthma risk was associated with higher adherence to a high-quality dietary pattern (relative risk [RR]: 0.91; 95 % confidence interval [CI]: 0.81 to 1.02). However, there was a substantial between-study heterogeneity (I² = 81.8 %, p < 0.001) and potential sources of heterogeneity were identified.

Differences between studies in measuring the incidence of asthma, as well as, in assessing dietary patterns are likely to be potential sources of heterogeneity. Nevertheless, with the currently available evidence a beneficial association between adherence to a healthy dietary pattern and lower risk of adult-onset asthma cannot be supported.