Dietary patterns and asthma prevalence, incidence and control

BACKGROUND: The increased asthma prevalence in westernized societies has been suggested to be related to environment exposures and lifestyle changes, particularly diet. We aimed to explore the association between dietary patterns and asthma prevalence, incidence and control in a nationally representative population. METHODS: Data from 32,644 adults, 53% female, from the 4th Portuguese National Health Survey were analysed. Prevalence of asthma was 5.3%; 'current asthma', defined by asthma symptoms within previous year, 3.5%; 'current medicated asthma' defined by use of asthma medication within previous year, 3.0%; 'current severe asthma' defined by emergency visit because of asthma within previous year, 1.4%; and 'incident asthma', 0.2%. Dietary patterns (DP) were identified by latent trait models based on dietary intake. Unconditional logistic regression models were performed to analyse association between DP and asthma. Age, gender, education, family income, proxy reporting information, smoking, body mass index and physical activity level were analysed as confounders. RESULTS: Two of the five identified DP were associated with asthma: 'high fat, sugar and salt' DP (positively correlated with pastry, chocolate and sweet desserts, candies, salty snacks, chips, fruit juices, soft drinks and alcoholic beverages consumption at snacks) was associated with asthma prevalence (OR = 1.13, 95% CI = 1.03, 1.24) and current severe asthma (OR = 1.23, 95% CI = 1.03, 1.48), while 'fish, fruit and vegetables' DP (positively correlated with fish, vegetables and fruit intake at meals) was negatively associated with current (OR = 0.84, 95% CI = 0.73, 0.98), and current medicated asthma (OR = 0.84, 95% CI = 0.72, 0.98), after adjustment for confounders. CONCLUSION & CLINICAL RELEVANCE: Our results suggest a protective association between 'fish, vegetables and fruit' DP and current asthma and current medicated asthma, and a detrimental association between 'high fat, sugar and salt' DP and severe asthma prevalence, further supporting the rational for diet and lifestyle intervention studies in asthma based on whole dietary patterns and physical activity.