PURPOSE: Obesity is a rapidly growing epidemic worldwide. Increasingly, studies have suggested an association between obesity and insufficient sleep. Most studies, however, have involved non-obese populations without known sleep disorders. We hypothesized that in patients referred for polysomnography (PSG), we would find a relationship between body mass index (BMI) and sleep duration.
METHODS: A prospective study of adult patients undergoing PSG at an urban academic medical center during February and March of 2006 was performed. Sleep questionnaires, consisting of questions related to sleep duration and behaviors leading up to bedtime, were given to all patients. Self-reported sleep duration was categorically reported as < 4 hours, 4-6 hours, 6-8 hours, 8-10 hours, and > 10 hours. Demographic information was also obtained, including age, gender, race, and co-morbid conditions. Data were analyzed by multiple linear regression models generated in SPSS.
RESULTS: 251 patients were available for analysis. Demographics: age 49 +/− 13 years old, 65% female, 46% Caucasian, 42% African American, 10% Hispanic. The average BMI was 39.5 kg/m2 and 92% were diagnosed as having obstructive sleep apnea. BMI was not predictive of total sleep duration in unadjusted (p=0.16) and adjusted analyses (p=0.46). However, increasing age (p=0.04) and African American race (p<0.001) were predictive of decreased sleep duration after adjusting for gender, caffeine and alcohol use before bedtime, co-morbidities, and the presence or absence of and severity of sleep apnea. After adjusting further for age, African Americans reported an average total sleep time less than Caucasians (odds ratio = 0.32).
CONCLUSION: In our population of patients referred for PSG, we did not find a relationship between self-reported sleep duration and BMI, though the population was morbidly obese. However, African-Americans, regardless of their age, BMI, degree of caffeine or alcohol use and severity of sleep apnea, reported less average sleep duration compared to Caucasians.
CLINICAL IMPLICATIONS: Further work is needed to understand the effects this decreased sleep has on quality of life and to explore the reasons why this phenomena exists.
DISCLOSURE: Ranju Chandrashekariah, None.