Abstract
BACKGROUND: The contribution of obesity to hypoxemia has not been reported in a community-based study. Our hypothesis was that increasing obesity would be independently associated with lower SpO2 in an ambulatory elderly population.
METHODS: The Cardiovascular Health Study ascertained resting SpO2 in 2,252 subjects over age 64. We used multiple linear regression to estimate the association of body mass index (BMI) with SpO2 and to adjust for potentially confounding factors. Covariates including age, sex, race, smoking, airway obstruction (based on spirometry), self reported diagnosis of emphysema, asthma, heart failure, and left ventricular function (by echocardiography) were evaluated.
RESULTS: Among 2,252 subjects the mean and median SpO2 were 97.6% and 98.0% respectively; 5% of subjects had SpO2 values below 95%. BMI was negatively correlated with SpO2 (Spearman R = −0.27, P < .001). The mean difference in SpO2 between the lowest and highest BMI categories (< 25 kg/m2 and ≥ 35 kg/m2) was 1.33% (95% CI 0.89–1.78%). In multivariable linear regression analysis, SpO2 was significantly inversely associated with BMI (1.4% per 10 units of BMI, 95% CI 1.2–1.6, for whites/others, and 0.87% per 10 units of BMI, 95% CI 0.47–1.27, for African Americans).
CONCLUSIONS: We found a narrow distribution of SpO2 values in a community-based sample of ambulatory elderly. Obesity was a strong independent contributor to a low SpO2, with effects comparable to or greater than other factors clinically associated with lower SpO2.
Footnotes
- Correspondence: Vishesh K Kapur MD MPH, Division of Pulmonary and Critical Care Medicine, University of Washington, Box 359803, 325 Ninth Avenue, Seattle WA 98104.
This research was partly supported by National Institutes of Health grants N01-HC-85239, N01-HC-85079 through N01-HC-85086, N01-HC-35129, N01 HC-15103, N01-HC-55222, N01-HC-75150, N01-HC-45133, National Heart, Lung, and Blood Institute grant HL080295, the National Institute of Neurological Disorders and Stroke, and National Institute on Aging grants AG-023629, AG-15928, AG-20098, and AG-027058. The Cardiovascular Health Study principal investigators and institutions are listed at http://www.chs-nhlbi.org/pi.htm.
Dr Fan has disclosed a relationship with Uptake Medical. Dr Au has disclosed a relationship with Gilead Sciences. The other authors have disclosed no conflicts of interest. The views herein are those of the authors and do not represent the Department of Veterans Affairs.
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