Prevalence of sleep abnormalities and their association among hypothyroid patients in an Indian population

Abstract

To estimate the prevalence of sleep abnormalities and their association with hypothyroidism and metabolic risk factors in a relatively lean urban South Indian population. This population-based, cross-sectional study was carried out in the urban population of Chennai, one of the largest metropolitan cities of India. Phase 1 was conducted in the field and involved a door-to-door survey of 26,000 individuals. In phase 2, every tenth subject recruited in phase 1 (n=2600) was invited to our centre for detailed anthropometric and biochemical measurements. For the current study, a subset of 358 subjects with positive family history of hypothyroidism was randomly selected. A validated questionnaire assessing various sleep abnormalities (snoring, daytime sleepiness, lack of refreshing sleep and number of hours of sleep) was administered. Anthropometric and biochemical measurements were obtained to assess metabolic risk factors including thyroid status. Snorers were more often male, older, smokers and had higher BMI, neck circumference, blood pressures, and hypothyroidism. Out of 358 patients, 133 had impaired thyroid function (37.1%) and 64 patients had both snoring and impaired thyroid function (17.8%). Subjects with daytime sleepiness had higher BMI and neck obesity. The overall prevalence of snoring and daytime sleepiness was 52% and 64%, respectively. Both sleep measures were associated with hypothyroid status. Metabolic syndrome was significantly associated with snoring even after adjusting for age, sex, family history of hypothyroidism, physical activity, smoking and alcohol. The prevalence of snoring and daytime sleepiness is high among urban South Indians who are relatively lean. Both disorders are associated with hypothyroidism, although these associations were stronger in those with obesity. Based on our case prevalence and the other reports cited previously, we can reasonably conclude that thyroid screening of sleep clinic patients is essential.