Depression and sleep-related symptoms in an adult, indigenous, North American population.

STUDY OBJECTIVES: Symptoms related to sleep disorders are common and may have substantial adverse impacts on mental health. Indigenous North Americans (American Indian) are a medically vulnerable population with reduced access to healthcare services. The purposes of this study were to assess (1) the prevalence of sleep symptoms and (2) the relationships between symptoms and depression in this population.

METHODS: We performed a community-based, door-to-door, cross-sectional survey of 3 indigenous North American groups (Gitxsan, Nisga'a and Tsimshian) living in the northwestern part of British Columbia. Between May and September of 2006, subjects completed a comprehensive questionnaire that included questions about sleep habits, medical history, subjective sleepiness (Epworth Sleepiness Scale), and depression (Personal Health Questionnaire [PHQ-9]). Weights and heights were also measured.

RESULTS: Four hundred thirty adults participated in the study (response rate = 42%). Their mean age was 43.2 years. Three hundred ninety-three agreed to have heights and weights measured. Their mean body mass index (BMI) was 31.0 +/- 9.2 kg/m2; 45% of them (177/393) were obese (BMI > 30 kg/m2), and 11% (43/393) were morbidly obese (BMI > 40 kg/m2). The prevalence of sleep complaints was high; insomnia symptoms was reported by 17.2%, symptoms of restless legs syndrome (RLS) by 17.7%, and frequent witnessed apneas reported (i.e., being told they stopped breathing at least 3 nights per week) by 7.6%. Of the 76 patients who had RLS symptoms, only 3 (3.9%) reported having received a diagnosis of RLS from a physician. Thirty-three subjects reported having frequent witnessed apneas, but only 5 of them (15.1%) reported having received a diagnosis of OSA from a physician. The mean PHQ9 score was 4.86 +/- 5.13 (reported by 389 subjects). Twenty-eight subjects (7.20%) had moderate to severe depression, with a PHQ-9 score of 15 or greater. In multivariable linear regression analysis, insomnia symptoms, witnessed apneas, and RLS symptoms were independently associated with an increase in PHQ9 score; frequent witnessed apneas were associated with an increase in PHQ9 by 2.46 (95% confidence interval: 0.47-4.46), insomnia symptoms by 4.49 (95% confidence interval: 3.14-5.83), and RLS symptoms by 1.82, (95% confidence interval: 0.53-3.12).

CONCLUSIONS: Sleep symptoms and depression are common in the indigenous North American population of northern British Columbia. Sleep-related symptoms (insomnia symptoms, witnessed nocturnal apneas, and RLS symptoms) are independently associated with depression scores. Improving access to sleep-related diagnostic and therapeutic services may substantially improve mental health in this vulnerable patient population.