Abdominal adiposity and obstructive airway disease: testing insulin resistance and sleep disordered breathing mechanisms

Haren, Matthew T., Misan, Gary, Paterson, Tracey-Jayne, Ruffin, Richard E., Grant, Janet F., Buckley, Jonathan D., Howe, Peter R.C., Newbury, Jonathan, Taylor, Anne W., and McDermott, Robyn A. (2012) Abdominal adiposity and obstructive airway disease: testing insulin resistance and sleep disordered breathing mechanisms. BMC Pulmonary Medicine, 12. 31. pp. 1-11.

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Abstract

Background: This study examined associations of abdominal adiposity with lung function, asthma symptoms and current doctor-diagnosed asthma and mediation by insulin resistance (IR) and sleep disordered breathing (SDB).

Methods: A random sample of 2500 households was drawn from the community of Whyalla, South Australia (The Whyalla Intergenerational Study of Health, WISH February 2008 - July 2009). Seven-hundred twenty-two randomly selected adults (>= 18 years) completed clinical protocols (32.2% response rate). Lung function was measured by spirometry. Post-bronchodilator FEV1/FVC was used to measure airway obstruction and reversibility of FEV1 was calculated. Current asthma was defined by self-reported doctor-diagnosis and evidence of currently active asthma. Symptom scores for asthma (CASS) and SDB were calculated. Intra-abdominal fat (IAF) was estimated using dual-energy x-ray absorptiometry (DXA). IR was calculated from fasting glucose and insulin concentrations.

Results: The prevalence of current doctor-diagnosed asthma was 19.9% (95% CI 16.7 - 23.5%). The ratio of observed to expected cases given the age and sex distribution of the population was 2.4 (95% CI 2.1, 2.9). IAF was not associated with current doctor-diagnosed asthma, FEV1/FVC or FEV1 reversibility in men or women but was positively associated with CASS independent of IR and SDB in women. A 1% increase in IAF was associated with decreases of 12 mL and 20 mL in FEV1 and FVC respectively in men, and 4 mL and 7 mL respectively in women. SDB mediated 12% and 26% of these associations respectively in men but had minimal effects in women.

Conclusions: In this population with an excess of doctor-diagnosed asthma, IAF was not a major factor in airway obstruction or doctor-diagnosed asthma, although women with higher IAF perceived more severe asthma symptoms which did not correlate with lower FEV1. Higher IAF was significantly associated with lower FEV1 and FVC and in men SDB mechanisms may contribute up to one quarter of this association.

Item ID: 35784
Item Type: Article (Research - C1)
ISSN: 1471-2466
Keywords: airway obstruction, forced Expiratory Volume, Forced Vital Capacity, asthma, abdominal adiposity, sleep disordered breathing
Additional Information:

© 2012 Haren et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Funders: South Australian Premiers Science Research Fund (RAM), National Health and Medical Research Council of Australia (NHMRC)
Projects and Grants: NHMRC Training Fellowship #511345
Date Deposited: 15 Oct 2014 16:48
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111799 Public Health and Health Services not elsewhere classified @ 100%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920499 Public Health (excl. Specific Population Health) not elsewhere classified @ 100%
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