Prevalence and risk factors for insomnia among Portuguese adolescents

Epidemiologic studies have shown that insomnia is the most prevalent sleep disorder at all ages, associated with sociodemographic and environmental factors and lifestyle. The aim of this study was to quantify the prevalence of insomnia and analyze its determinants among Portuguese adolescents. In a cross-sectional study, we evaluated 6,919 students from the 7th to the 12th grade from 26 secondary schools, during 2012. Data were collected using a self-administered questionnaire. Insomnia was defined based on the Diagnostic and Statistical Manual of Mental Disorders IV criteria. Prevalences were expressed in proportions with 95 % confidence intervals (CI), and the magnitude of association between variables was detailed using odds ratio (OR). The prevalence of symptoms of insomnia was 21.4 %, and the prevalence of insomnia was 8.3 %. After adjustment for gender and age, insomnia was associated with female gender (adjusted OR = 1.82; CI 95 %: 1.56-2.13), age ≥ 16 years (adjusted OR = 1.17; CI 95 %: 1.01-1.35), coffee and alcohol consumption (adjusted OR = 1.40; CI 95 %: 1.20-1.63 and adjusted OR = 1.21; CI 95 %: 1.03-1.41, respectively), and depressive symptoms (adjusted OR = 3.59; CI 95 %: 3.04-4.24).

The high prevalence of insomnia in our sample of Portuguese adolescents confirms findings from epidemiologic studies that have shown insomnia to affect from 4.4 to 13.4 % of adolescents. The main risk factors for insomnia among these adolescents are gender (female), age (≥ 16 years), depression, and coffee and alcohol consumption, which is also in concordance with those in the literature.