ATS 2013, PHILADELPHIA ─ A new study from researchers in Japan indicates that obstructive sleep apnea (OSA) is independently associated with visceral (abdominal) fat accumulation only in men, perhaps explaining gender differences in the impact of OSA on cardiovascular disease and mortality.
"Visceral fat accumulation, which is a risk factor for cardiovascular disease, is also associated with OSA, and gender differences in mortality related to sleep apnea have been reported in some studies. Accordingly, we examined if the relationship between OSA and visceral fat accumulation differed by gender," said Drs. Yuka Harada, MD and Kazuo Chin MD.PhD, of the Kyoto University Graduate School of Medicine. "We found that visceral fat accumulation was associated with OSA in men, but not in women."
The study results will be presented at the ATS 2013 International Conference in Philadelphia.
The study enrolled 271 male and 100 female patients who were evaluated for OSA between October 2008 and December 2010.
Body mass index (BMI) and waist circumference were similar in men and women. Compared with women, men had greater visceral fat accumulation, more severe OSA, and more severe dyslipidemia.
Statistical analyses of the relationships between OSA and fat accumulation revealed that in men, age, BMI, and two indicators of OSA (minimum oxygen saturation during sleep and alveolar-arterial oxygen difference) were independently associated with visceral fat accumulation, while in women, only BMI was associated with visceral fat accumulation.
Measurements of subcutaneous fat were related to BMI in both men and women, but were not related to OSA parameters.
"The complex relationship between OSA and obesity is well documented," said Drs Harada and Chin. "If our findings that visceral fat accumulation is associated with OSA only in men are confirmed in further studies, it may help in the development of new prognostic tools and treatment approaches in this population."
* Please note that numbers in this release may differ slightly from those in the abstract. Many of these investigations are ongoing; the release represents the most up-to-date data available at press time.
Type: Scientific Abstract
Category: 16.04 - Sleep Disordered Breathing: Epidemiology, Genetics and Outcomes (SRN)
Authors: Y. Harada1, T. Oga1, Y. Chihara2, S. Hamada1, M. Azuma1, Y. Toyama1, K. Murase1, K. Tanizawa1, C. Yoshimura1, T. Hitomi1, T. Handa1, M. Mishima1, K. Chin1; 1Graduate School of Medicine, Kyoto University - Kyoto/JP, 2Otsu Red Cross Hospital - Otsu/JP
RATIONALE: Gender difference in mortality from obstructive sleep apnea (OSA) is an important issue. Visceral fat accumulation, a significant risk factor for cardiovascular disease (CVD), was reported to be closely related to OSA. Thus, we hypothesized that the association between OSA and visceral fat differed by gender, possibly affecting gender differences in OSA-related CVD and mortality. We examined by gender which factors were independently associated with visceral fat accumulation in OSA.
METHODS: Subjects were 271 males and 100 females consecutively hospitalized for examination of OSA from October 2008 to December 2010. In the first 308 subjects, relationships were analyzed between fat areas by computed tomography, comorbidity, polysomnographic data, arterial blood gas, pulmonary function and venous blood data. Multiple regression analyses were performed to identify those variables independently associated with visceral fat area (VFA) and subcutaneous fat area (SFA) for each gender. Additionally, we devised prediction formulas for VFA and SFA from our results and validated these formulas in the latter 63 subjects.
RESULTS: Despite similar body mass index (BMI) and waist circumference, men had larger VFA, more severe OSA and more severe dyslipidemia than women. Multiple regression analyses revealed that in men, not only age and BMI but also minimum oxygen saturation (contribution rate (R2) = 4.7%) during sleep, and alveolar-arterial oxygen difference (R2 = 6.3%) were independently associated with VFA. Conversely, VFA was only associated with BMI in women. In both genders, SFA were associated with BMI, not with OSA-related parameters (Figure 1) . Moreover, values of predicted VFA and SFA from multiple regression function were very close to actual measured values in the latter subjects (r = 0.6-0.9, p < 0.001).
CONCLUSIONS: Only in men was OSA independently associated with VFA. The lesser effect of OSA on visceral fat in women might account for lower impact of OSA on CVD or mortality in women.