Obesity Is Associated With a Lower Resting Oxygen Saturation in the Ambulatory Elderly: Results From the Cardiovascular Health Study

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 S_pO2 in an ambulatory elderly population.

METHODS:

The Cardiovascular Health Study ascertained resting S_pO2 in 2,252 subjects over age 64. We used multiple linear regression to estimate the association of body mass index (BMI) with S_pO2 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 S_pO2 were 97.6% and 98.0% respectively; 5% of subjects had S_pO2 values below 95%. BMI was negatively correlated with S_pO2 (Spearman R = −0.27, P < .001). The mean difference in S_pO2 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, S_pO2 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 S_pO2 values in a community-based sample of ambulatory elderly. Obesity was a strong independent contributor to a low S_pO2 , with effects comparable to or greater than other factors clinically associated with lower S_pO2 .