The bidirectional association between insomnia and gastroesophageal reflux symptoms, the HUNT study, Norway

INTRODUCTION: Gastroesophageal reflux symptoms (GERS) and insomnia are associated, but although a bidirectional association has been suggested, no studies have addressed this issue. Our aim was to investigate this potential bidirectional association in a large population-based cohort study. 

METHODS: The study is based on a longitudinal cohort study (HUNT) conducted in the county of Nord-Trøndelag, Norway, including HUNT2 (1995-1997) and HUNT3 (2006-2008). All adult county residents were invited to answer questionnaires about their health and diseases, including insomnia and GERS. First, we studied incidence of GERS in HUNT3 among participants without GERS in HUNT2 but exposed to insomnia (N=15,310). Second, we investigated the incidence of insomnia in HUNT3 among participants without insomnia in HUNT2 but with GERS (N=18,520). Logistic regression was used to estimate odds ratios (ORs) with 95% confidence intervals (CIs) adjusted for age, sex, tobacco smoking, education and body mass index (BMI).   

RESULTS: During a mean of 11 years study period 4,566 (30%) participants reported GERS and 501 (3%) insomnia. The adjusted OR of incident GERS was 2.14 (95% CI 1.46-3.14) among participants with persistent insomnia (i.e. in both HUNT2 and HUNT3), 1.56 (95% CI 1.27- 1.91) among participants with insomnia in HUNT2 only, and 1.70 (95% CI 1.39-2.07) among those with insomnia in HUNT3 only, compared to those without insomnia. The adjusted OR of insomnia was 2.14 (95% CI 1.70-2. 70) among participants with persistent GERS, 1.53 (95% CI 1.07-2.19) among those with GERS in HUNT2 only, and 1.63 (95% CI 1.31-2.12) among those with GERS in HUNT3 only, compared with those without GERS.   

CONCLUSIONS: There seems to be bidirectional associations of similar strengths between insomnia symptoms and GERS and GERS and insomnia. Persistent presence of the other disorder increases the risk about 2-fold.