C-reactive protein, obesity, atopy and asthma symptoms in middle-aged British adults

¹ Division of Community Health Sciences, St George's, University of London, Cranmer Terrace, Tooting, London SW17 ORE, UK

^* To whom correspondence should be addressed. E-mail: d.strachan{at}sgul.ac.uk.

	Abstract

Recent research suggested an association between circulating C-reactive protein (CRP) and adult asthma, confined to those without evidence of allergic predisposition. We investigated the role of smoking and obesity as explanations for this relationship.

At age 44–45, members of the British 1958 birth cohort participated in a biomedical survey involving the measurement of CRP, specific IgE to grass, cat and dust mite, standing height and weight. Information on asthma and related symptoms was collected by computer aided interview at age 42. Complete data were available for 6490 subjects.

CRP levels were positively correlated with body mass index (BMI), higher among women than men and among heavy smokers (>=20 cigarettes·day^-1) than never smokers. Adjusted for sex and region, odds ratios comparing asthma prevalence in subjects above the fourth CRP quartile with subjects below the first were 1.85 (95% confidence interval 1.15 to 2.99) for non-atopics and 0.94 (0.62 to 1.41) for atopics changing to 1.36 (0.80 to 2.32) and 1.07 (0.67 to 1.69) respectively when additionally adjusted for smoking and BMI.

Any association between CRP and asthma prevalence confined to non-atopics may be due to confounding or may reflect a more general association of CRP with smoking-related obstructive airways disease.