Association between indoor noise level at night and objective/subjective sleep quality in the older population: a cross-sectional study of the HEIJO-KYO cohort

STUDY OBJECTIVES: Noise exposure could be an important risk factor for low sleep quality; however, evidence on indoor noise in large-scale populations is limited. We evaluate the association between indoor noise at night and objective and subjective sleep quality in the older population. METHODS: In this cross-sectional study of 1076 participants (≥60 years), we measured indoor noise at night (A-weighted equivalent noise from bedtime to rising time [L(Aeq)]) using a portable noise level meter set in bedrooms and sleep quality using actigraphy and a questionnaire for 2 nights. Using multivariable linear regression models, we examined the associations between indoor noise at night and objective and subjective sleep parameters independent of potential confounders such as age, body mass index, and sleep medication. RESULTS: Increased indoor noise at night by 1 dB of L(Aeq) was significantly associated with lower objective sleep quality, such as lower sleep efficiency (regression coefficient [β], −0.19%; 95% confidence interval [95% CI], −0.26 to −0.12; p < 0.001), longer log-transformed sleep onset latency (β, 0.02 log min; 95% CI 0.01 to 0.03; p< 0.001) and wake after sleep onset (β, 0.66 min; 95% CI 0.40 to 0.92; p < 0.001), and higher log-transformed fragmentation index (β, 0.01; 95% CI 0.008 to 0.017; p < 0.001). These results remained consistent in the analysis using noise-event rate (≥45 dB) as an independent variable. CONCLUSION: This study revealed the quantitative association between indoor noise at night and objective and subjective sleep quality in the older population. Reducing noise and improving sleep quality may prevent fatal diseases.