0743 Association of Circadian Timing with Incident Dementia: The Korean Genome and Epidemiology Study

Abstract Introduction Circadian rhythm disruption is common in neurodegenerative disorders such as dementia. Especially, preference for circadian timing (e.g., chronotype) mainly affects cognitive and memory function. Previous studies reported that individuals with earlier chronotype may be useful predictor of poor neurocognitive outcomes and accelerated brain aging, but there is still not adequate strong evidence regarding the relationship between chronotype and dementia. The aim of the present study is to examine the associations between different chronotype and incident dementia through middle-aged to older general population. Methods A total 9541 participants of the Korean Genome and Epidemiology Study – Ansan and Ansung (mean age, 52.2±8.9), who have been linked to the Health Insurance Review and Assessment Service national database to assess incident all-cause and sub-type of dementia were analyzed. The mid-point sleep (MST) was defined as the midpoint between bedtime and wake time and used to categorize the participants into three groups (earlier-, intermediate-, and later-type). In multivariate Cox regression analysis, we adjusted for age, sex, area, marital status, education level, body mass index, smoking and drinking status, regular exercise, hypertension, diabetes, depression, hyperlipidemia, heart, and cerebrovascular disease at baseline. Results During the mean follow-up of 17.7 years, dementia was diagnosed in 1236 participants (588 with Alzheimer's disease (AD)). Among total participants at baseline, 13.0% were 65-69 years of age and 52.9% were women. Compared to the intermediate-type (-1SD (1.3 h) ≤ MST ≤ +1SD (3.6 h)), adjusted hazard ratio (HR) of all-cause dementia were 1.19 (95% CI, 1.04-1.36) in the earlier-type (<-1SD). In addition, earlier-type was associated with greater risk of AD (HR = 1.22; 95% CI, 1.02-1.47). However, these associations were not shown in later chronotype (>+1SD). Conclusion Our findings suggest that early mid-point of sleep was prospectively associated with an increased risk of all-cause dementia and Alzheimer’s disease among middle-aged or older adults. Support (if any) This study was supported by the Korea Centers for Disease Control and Prevention (2001-347-6111-221, 2002-347-6111-221); Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2020R1I1A1A01071011 and NRF-2022R1I1A1A01065700); National Institutes of Health (NIH) (RF1NS120947); Health Insurance Review and Assessment Service research data (NHIS-2023-1-600).