Obesity, waist size and prevalence of current asthma in the California Teachers Study cohort
- J Von Behren1,
- M Lipsett2,
- P L Horn-Ross1,3,
- R J Delfino4,
- F Gilliland5,
- R McConnell5,
- L Bernstein6,
- C A Clarke1,3,
- P Reynolds1,3
- 1Northern California Cancer Center, Berkeley and Fremont, California, USA
- 2Environmental Health Investigations Branch, California Department of Public Health, Richmond, California, USA
- 3Department of Health Research and Policy, Stanford University School of Medicine, Stanford, California, USA
- 4Department of Epidemiology, School of Medicine, University of California, Irvine, California, USA
- 5Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- 6Department of Cancer Etiology, City of Hope National Medical Center, Duarte, California, USA
- Correspondence to Ms J Von Behren, Northern California Cancer Center, 2001 Center Street, Suite 700, Berkeley, CA 94704, USA; jvonbehren{at}nccc.org
- Received 29 January 2009
- Accepted 6 July 2009
- Published Online First 25 August 2009
Abstract
Background: Obesity is a risk factor for asthma, particularly in women, but few cohort studies have evaluated abdominal obesity which reflects metabolic differences in visceral fat known to influence systemic inflammation. A study was undertaken to examine the relationship between the prevalence of asthma and measures of abdominal obesity and adult weight gain in addition to body mass index (BMI) in a large cohort of female teachers.
Methods: Prevalence odds ratios (ORs) for current asthma were calculated using multivariable linear modelling, adjusting for age, smoking and race/ethnicity.
Results: Of the 88 304 women in the analyses, 13% (n = 11 500) were obese (BMI ≥30 kg/m2) at baseline; 1334 were extremely obese (BMI ≥40 kg/m2). Compared with those of normal weight, the adjusted OR for adult-onset asthma increased from 1.40 (95% confidence interval (CI) 1.31 to 1.49) for overweight women to 3.30 (95% CI 2.85 to 3.82) for extremely obese women. Large waist circumference (>88 cm) was associated with increased asthma prevalence, even among women with a normal BMI (OR 1.37, 95% CI 1.18 to 1.59). Among obese women the OR for asthma was greater in those who were also abdominally obese than in women whose waist was ≤88 cm (2.36 vs 1.57). Obese and overweight women were at greater risk of severe asthma episodes, measured by urgent medical visits and hospital admissions.
Conclusions: This study confirms the association between excess weight and asthma severity and prevalence, and showed that a large waist was associated with increased asthma prevalence even among women considered to have normal body weight.
Footnotes
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Funding National Cancer Institute (R01 CA77398, R01 CA105224).
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Competing interests None.
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Provenance and Peer review Not commissioned; not externally peer reviewed.
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Ethics approval The use of human subject data was approved by the California Committee for the Protection of Human Subjects and the institutional review boards of the participating institutions.
