Sleep Apnea in Look AHEAD (Action for Health in Diabetes)

The duration of the study is 5 years; participants will be enrolled in the study for a total of 2 years. Recruitment will be based on the protocol set forth in the larger Look AHEAD trial that will occur in 8 treatment waves, spaced approximately 4 months apart. Each of these waves at the Penn site will include 40 people, making the potential subject pool approximately 320 persons.

Participants at the Penn site will be approximately 44 men and women, between 45 and 75 years of age, with a body mass index (BMI) > 25 kg/m2. All subjects will be obese type 2 diabetics who have been randomly assigned to the Lifestyle Intervention Group or the Diabetes Education and Support Group in the Look AHEAD Study. Therefore, the inclusion and exclusion criteria are determined by the parent study. Patients who are currently being treated for OSA (e.g., continuous positive airway pressure) or who have had surgical treatment for OSA will be excluded. Patients who have been previously diagnosed with OSA but are not being treated will be included. These 44 individuals represent a subset of the approximately 320 persons who will be treated at the University of Pennsylvania site.

As part of the baseline visit (before randomization) for the Look AHEAD study, Look AHEAD participants will be asked to sign a consent form for screening. Consenting participants will complete the Multivariate Apnea Prediction Form. The MAP includes weight, height, age and 3 questions about sleep-related symptoms. After the prescreen consent has been completed, the Research Coordinator will invite the participant to complete the consent form for this study. Interested subjects will be scheduled to meet with this study's Research Coordinator during the subject's next scheduled Look AHEAD visit. Participants wishing to enroll will undergo the baseline assessments and be scheduled for their baseline sleep study. Subjects will be paid $50 for this sleep assessment. After completion of the baseline sleep study, the results will be analyzed. Thirty subjects with a baseline RDI > 15 and 28 subjects with an RDI between 5 and 15 (5 < RDI < 15) will continue in the study, undergoing the same assessments at years 1 and 2.

Obstructive sleep apnea (OSA) is a syndrome characterized by frequent cessations of airflow during sleep (despite continued respiratory effort) that are caused by the closure of the pharyngeal airway. The most frequently used metric to describe OSA is the respiratory disturbance index (RDI) (sometimes referred to as the apnea-hypopnea index or AHI). RDI is defined as the average number of apnea/hypopnea events per hour of sleep. The medical consequences of OSA include an increased risk of hypertension, stroke, myocardial infarction, and premature mortality. The behavioral and psychosocial consequences of OSA include excessive daytime sleepiness, depression, sexual dysfunction, and a 3-7 fold increase in the risk of motor vehicle accidents. Among 30 to 60 year olds, 9% of women and 24% of men in the general population have an RDI > 5. The serious consequences and high prevalence of OSA clearly constitute a major public health problem.

OSA is strongly related to obesity, an important public health problem in its own right. In a series of 1000 OSA patients, two thirds had body weights > 30% above recommended. Several studies have identified body mass index (BMI) as the strongest predictor of RDI. Data from the Wisconsin Sleep Cohort Study revealed that a one standard deviation increase in BMI was associated with a four-fold increase in the risk of having an RDI > 5. Among obese patients seeking weight loss treatment, nearly 40% exhibited evidence of SDB, and 10% required treatment for OSA. The link between obesity and SDB is further supported by data showing that weight loss significantly improves SDB in obese patients with OSA. Perhaps the most compelling data about the effects of weight change on SDB, particularly weight gain, come from a very recent study of the Wisconsin Sleep Cohort that examined changes in weight and SDB over 4 years in a community sample of 690. On average, the sample experienced a 3 kg weight gain and 1.4/hr increase in RDI. Across the entire sample, on average, a 1% change in body weight was associated with a 3% change in RDI. Participants who reduced body weight by 10% experienced a 26% reduction in RDI, while those who increased body weight by 10% experienced a 32% increase in RDI. A 10% weight gain was associated with a 6-fold increase in the risk of developing a RDI > 15. These descriptive, longitudinal data are suggestive of the benefits of weight loss on SDB, but several factors limit conclusions about the effects of weight loss on obese OSA patients. First, the initial mean RDI was 4.1, so very few subjects (n = 46) had moderate or severe OSA (RDI > 15). Further, only a small number of subjects (n = 61) lost > 5% of initial body weight. Finally, similar to the broader literature on the effects of weight loss, this study is limited by the lack of a no-weight loss control group and the inability to distinguish intentional from non-intentional weight loss.