Dietary patterns and adult asthma: population-based case-control study.
BACKGROUND
Epidemiological studies of diet and asthma have focused on relations with intakes of individual nutrients and foods and evidence has been conflicting. Few studies have examined associations with dietary patterns.


METHODS
We carried out a population-based case-control study of asthma in adults aged between 16 and 50 in South London, UK. Information about usual diet was obtained by food frequency questionnaire and we used principal components analysis to define five dietary patterns in controls. We used logistic and linear regression, controlling for confounders, to relate these patterns to asthma, asthma severity, rhinitis and chronic bronchitis in 599 cases and 854 controls.


RESULTS
Overall, there was weak evidence that a 'vegetarian' dietary pattern was positively associated with asthma [adjusted odds ratio comparing top vs bottom quintile of pattern score 1.43 (95% CI: 0.93-2.20), P trend 0.075], and a 'traditional' pattern (meat and vegetables) was negatively associated [OR 0.68 (0.45-1.03), P trend 0.071]. These associations were stronger amongst nonsupplement users (P trend 0.030 and 0.001, respectively), and the association with the 'vegetarian' pattern was stronger amongst whites (P trend 0.008). No associations were observed with asthma severity. A 'prudent' dietary pattern (wholemeal bread, fish and vegetables) was positively associated with chronic bronchitis [OR 2.61 (1.13-6.05), P trend 0.025], especially amongst nonsupplement users (P trend 0.002).


CONCLUSIONS
Overall there were no clear relations between dietary patterns and adult asthma; associations in nonsupplement users and whites require confirmation. The finding for chronic bronchitis was unexpected and also requires replication.
National Heart and Lung Institute, Imperial College London, UK.
I
I
Bakolis
R
R
Hooper
R L
RL
Thompson
S O
SO
Shaheen
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology*; D029481:Bronchitis, Chronic / Q000453:epidemiology / Q000209:etiology; D016022:Case-Control Studies; D004032:Diet / Q000009:adverse effects*; D019587:Dietary Supplements / Q000009:adverse effects; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D025341:Principal Component Analysis; D011795:Surveys and Questionnaires; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult