Keun Hye Jeon, MD¹; Kyungdo Han, PhD²; Su-Min Jeong, MD^3,4,5; Junhee Park, MD⁶; Jung Eun Yoo, MD, PhD⁷; Juhwan Yoo, MS⁸; Jinkook Lee, MD^9,10; SangYun Kim, MD¹¹; Dong Wook Shin, MD, DrPH, MBA^6,12

¹Department of Family Medicine, Cha Gumi Medical Center, Cha University, Gumi, Republic of Korea
²Department of Statistics and Actuarial Science, Soongsil University, Seoul, Republic of Korea
³Department of Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea
⁴Department of Family Medicine, Seoul National University Health Service Center, Seoul, Republic of Korea
⁵Department of Family Medicine, Seoul National University Hospital, Seoul, Republic of Korea
⁶Department of Family Medicine/Supportive Care Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
⁷Department of Family Medicine, Healthcare System Gangnam Center Seoul National University Hospital, Seoul, Republic of Korea
⁸Department of Medical Statistics, The Catholic University of Korea, Seoul, Republic of Korea
⁹Department of Economics, Center for Economic & Social Research, University of Southern California, Los Angeles
¹⁰RAND Corporation, Santa Monica, California
¹¹Department of Neurology, Seoul National University Bundang Hospital & Seoul National University College of Medicine, Seongnam, Republic of Korea
¹²Department of Clinical Research Design and Evaluation, Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University, Seoul, Republic of Korea

Corresponding Authors: Dong Wook Shin, MD, DrPH, MBA ; Kyungdo Han, PhD

Importance: The impact of serial changes in alcohol consumption on dementia risk has rarely been investigated to date.

Objective: To investigate the association of comprehensive patterns of changes in alcohol consumption with the incidence of all-cause dementia, Alzheimer disease (AD), and vascular dementia (VaD).

Design, setting, and participants: This is a retrospective cohort study. Data were obtained from the Korean National Health Insurance Service database. Adults aged 40 years and older underwent 2 health examinations in 2009 and 2011. The cohort was assessed until December 31, 2018, and statistical analysis was performed in December 2021.

Exposures: Alcohol consumption level was categorized into none (0 g per day), mild (<15 g per day), moderate (15-29.9 g per day), and heavy (≥30 g per day) drinking. On the basis of changes in alcohol consumption level from 2009 to 2011, participants were categorized into the following groups: nondrinker, quitter, reducer, sustainer, and increaser.

Main outcomes and measures: The primary outcome was newly diagnosed AD, VaD, or other dementia.

Results: Among 3 933 382 participants (mean [SD] age, 55.0 [9.6] years; 2 037 948 men [51.8%]), during a mean (SD) follow-up of 6.3 (0.7) years, there were 100 282 cases of all-cause dementia, 79 982 cases of AD, and 11 085 cases of VaD. Compared with sustained nondrinking, sustained mild (adjusted hazard ratio [aHR], 0.79; 95% CI, 0.77-0.81) and moderate (aHR, 0.83; 95% CI, 0.79-0.88) drinking were associated with a decreased risk of all-cause dementia, whereas sustained heavy drinking was associated with an increased risk of all-cause dementia (aHR, 1.08; 95% CI, 1.03-1.12). Compared with sustained levels of drinking, reducing alcohol consumption from a heavy to a moderate level (aHR, 0.92; 95% CI, 0.86-0.99) and the initiation of mild alcohol consumption (aHR, 0.93; 95% CI, 0.90-0.96) were associated with a decreased risk of all-cause dementia. Increasers and quitters exhibited an increased risk of all-cause dementia compared with sustainers. The trends in AD and VaD remained consistent.

Conclusions and relevance: In this cohort study of a Korean population, decreased risk of dementia was associated with maintaining mild to moderate alcohol consumption, reducing alcohol consumption from a heavy to a moderate level, and the initiation of mild alcohol consumption, suggesting that the threshold of alcohol consumption for dementia risk reduction is low.