Longitudinal study of diet quality and change in asthma symptoms in adults, according to smoking status

Abstract

It has been hypothesised that increased asthma prevalence in westernised countries is associated with changes in lifestyle factors, including a poorer diet. However, little is known regarding the association between diet quality and asthma. In the diet-asthma association, the role of BMI as a potential mediator needs clarification; moreover, potential effect modification by non-diet sources of oxidants, such as smoking, merits investigation. We investigated the association between diet quality and change in asthma symptoms, as well as assessed effect modification by smoking, while accounting for BMI as a potential mediator. Using data from the French prospective Epidemiological study on the Genetics and Environment of Asthma study, we assessed diet quality using the Alternate Healthy Eating Index 2010 (AHEI-2010) at baseline and change in asthma symptoms (stable (reference), worsening, improved; mean follow-up time: 7 years). Mediation analysis was used to disentangle total and direct effects and the indirect effect mediated by BMI. The analyses included 969 adults (mean age 43 years; 49 % men; 42 % ever asthma). We observed a significant interaction between smoking and AHEI-2010 on change in asthma symptoms (P for interaction=0·04). Among never smokers (n 499), we observed a positive total effect (multivariable OR 1·39; 95 % CI 1·07, 1·80) and a positive direct effect (OR 1·41; 95 % CI 1·09, 1·80) of the AHEI-2010 (per ten-point increment) on improved symptoms. No indirect effect mediated through BMI was observed (OR 0·99; 95 % CI 0·91, 1·07). Among former and current smokers, all effects were statistically non-significant. Better diet quality was associated with improved asthma symptoms over time in never smokers, independently of BMI.

Lifestyle interventions in prevention and comprehensive management of COPD

“…High consumption of fruits and vegetables is associated with reduced COPD incidence in both current and ex-smokers, but not in never-smokers [70]. Better diet quality is associated with improved asthma symptoms over time in never-smokers, independent of BMI [71]. Current evidence suggests a positive impact of agriculture-based food security programmes on dietary indicators in low and lower-middle income countries [72].…”

Associations between dietary scores with asthma symptoms and asthma control in adults

“…Diet scores based on existing nutritional knowledge have thus been proposed to assess overall diet quality, providing a quantitative measure taking into account synergic effects among nutrient and food intakes [3]. Up to now, very few epidemiological studies have been conducted on the association between overall dietary scores and asthma phenotypes in adults [7][8][9][10][11][12] and, taken together, the level of evidence is still poor. Discrepant findings are probably due to the complexity of assessment of both outcomes and exposures and, consequently, of their associations.…”

“…Regarding outcomes, only two studies investigated the role of overall diet quality as a primary prevention for asthma; however, they used different asthma definitions and reported discrepant findings [9,12]. The asthma symptom score, which is recommended for the study of risk factors in asthma [13,14], is particularly relevant in epidemiological studies investigating the diet-asthma association, as it can be used in participants both with and without asthma allowing integration of different asthma phenotypes and different levels of asthma prevention.…”

“…As a basis for secondary prevention studies, better understanding of the reasons why asthma is getting worse in a substantial proportion of patients would be very informative. According to the latest Global Initiative for Asthma (GINA) report, a healthy diet high in fruits and vegetables is encouraged for people with asthma due to its general health benefits [15]; however, up to now, very few studies have been conducted in adults regarding the role of diet quality in asthma control and they reported discrepant results [7,8,11,12].…”

“…International diet scores have been developed, including the Alternate Healthy Eating Index 2010 (AHEI-2010) and the literature-based adherence score to Mediterranean Diet (MEDI-LITE) [16]. The AHEI-2010, a measure of diet quality, has been widely used and is consistently associated with a lower risk of mortality and major chronic diseases, including chronic obstructive pulmonary disease (COPD) and asthma [9,12,17,18]. The MEDI-LITE has recently been proposed as a valid ambulatory instrument to assess adherence to the Mediterranean diet, which has been associated with better health [19].…”