A review of sleep-related indicators measured in large population-based cohort studies in Japan
Abstract
Background: How to measure sleep has been the primary focus of sleep epidemiological studies. To address the lack of systematic evaluation of sleep-related indicators, we reviewed large population-based cohort studies in Japan, focusing on whether sleep was measured subjectively or objectively.
Methods: PubMed, Ichushi-Web, and official cohort study websites were systematically searched from January 1, 2004, to March 31, 2025, to identify studies that measured sleep-related indicators as exposures or outcomes in 19 large population-based cohorts in Japan. Data on sleep measurement methods and main study results were extracted.
Results: Of 102 studies in 12 cohorts, 75 (74%) studies examined subjective sleep quantity or quality based on questionnaires, and 27 (26%) used objective measures of sleep. Among subjective measures, sleep duration was frequently self-reported (57 studies in 10 cohorts), while sleep quality was directly (e.g., "Do you think you get enough sleep?") or indirectly asked as part of sleep-related scores such as the Pittsburgh Sleep Quality Index (51 studies in 10 cohorts). Regarding objective measures, the Circulatory Risk in Communities Study cohort measured 3% oxygen desaturation index by pulse oximetry (9 studies) and respiratory disturbance index by airflow monitor (1 study), Japan Multi-Institutional Collaborative Cohort Study used actigraphy (1 study), Nagahama cohort used pulse oximetry (12 studies) and actigraphy (13 studies), and Tohoku Medical…
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