Obesity is one of most important risk factors for obstructive sleep apnea syndrome (OSA). In this studys, we examined the importance of a rapid and considerable increase in body weight in OSA using a weight changing index (WCI). We investigated 39 patients (35 males and 4 females) that were referred to our hospital complaining of snoring and sleeping disturbance, and we employed body mass index (BMI) to evaluate obesity. The BMI was estimated as body weight divided by height to the second power: BMI (kg/m2)=body weight/(height * height). WCI was estimated as the previous BMI around the time the patients noticed sleeping disturbance, minus the present BMI. We evaluated degrees of OSA using the apnea-hypopnea index (AHI) as measured by polysomnography. We found a significant correlation between AHI and BMI, confirming that obesity greatly influences OSA. In younger subjects, the correlation between OSA and increases in WCI was more prominent than that in older subjects, whereas the BMI values did not differ significantly with age. Since WCI appeared to reflect the accumulation of visceral fat, we suggest that visceral-fat obesity most strongly influences OSA. The increasing prevalence of obesity is likely to produce social problems associated with a higher incidence of OSA. It is therefore important to develop suitable methods for the detection and treatment of OSA.
