| Title: | Associations between wearable-device-measured daytime and nighttime light exposures and dementia risk: A prospective cohort study |
| Journal: | General Psychiatry |
| Published: | 24 Jun 2026 |
| Pubmed: | https://pubmed.ncbi.nlm.nih.gov/42358626/ |
| DOI: | https://doi.org/10.1002/gps3.70039 |
Publication 20550
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Abstract
Background: Identifying reliable predictors for dementia remains a critical unmet need. Light exposure plays a crucial role in regulating circadian rhythms, which influence cognitive function. However, the association between light exposure and dementia risk remains unclear.</p>
Aims: This study examined the associations of daytime and nighttime light exposure with dementia risk.</p>
Methods: A total of 87 577 dementia-free participants (mean age: 62.36 years; 56.98% female) were included. Daytime and nighttime light exposures were measured using 7-day free-living wrist-worn accelerometry. Incident dementia was identified from primary care, hospital inpatient admissions and death registry data. Cox proportional hazards models assessed associations, and mediation analyses evaluated circadian rest-activity rhythms (CRARs), brain structures and vitamin D as potential mediators.</p>
Results: Over a median follow-up of 8.1 years, 741 participants developed dementia. Daytime light exposure above 1000 lux was associated with reduced dementia risk (hazard ratio [HR] 0.84, 95% confidence interval [CI] 0.71-0.99, p = 0.039). Longer exposure to brighter light (e.g., ≥ 0.70 h at ≥ 5000 lux; HR 0.83, p = 0.036) was associated with a further reduction in risk. In exploratory analyses, CRARs and brain structures mediated up to 33% of the association. Protective associations were stronger in those with high levels of nighttime light exposure, an evening chronotype or apolipoprotein E (APOE) ε4 carrier status, with a risk reduction of up to 41%. Furthermore, < 0.70 h per day of bright daytime light (≥ 5000 lux) outperformed six established dementia predictors (e.g., obesity, alcohol consumption, traumatic brain injury and so on). Nighttime light showed no significant association with dementia risk.</p>
Conclusions: High levels of daytime light exposure were significantly associated with lower dementia risk. Further research should explore its role in dementia screening and inform the development of light-based interventions.</p>
14 Authors
- Nana Zheng
- Wei Wang
- Biao Li
- Xionge Mei
- Yue Liu
- Jing Du
- Ngan Yin Chan
- Joey W. Y. Chan
- Xiaoman Xing
- Xiao Tan
- Christian Benedict
- Yun Kwok Wing
- Jihui Zhang
- Hongliang Feng
1 Application
| Application ID | Title |
|---|---|
| 58082 | Using Mendelian Randomization to investigate the causal associations between rest-activity patterns and common diseases |
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