Seasonal Variations in Vitamin D Levels and the Incident Dementia Among Older Adults Aged ≥60 Years in the UK Biobank

Jiahao Liu; Eddy Roccati; Yutong Chen; Zhuoting Zhu; Wei Wang; Mingguang He; Xianwen Shang

doi:10.3233/ADR-230077

Seasonal Variations in Vitamin D Levels and the Incident Dementia Among Older Adults Aged ≥60 Years in the UK Biobank

J Alzheimers Dis Rep. 2024 Mar 15;8(1):411-422. doi: 10.3233/ADR-230077. eCollection 2024.

Authors

Jiahao Liu¹, Eddy Roccati^{2

3}, Yutong Chen⁴, Zhuoting Zhu^{1

5}, Wei Wang⁶, Mingguang He^{1

5

6

7}, Xianwen Shang^{1

5}

Affiliations

¹ Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia.
² Wicking Dementia Research and Education Centre, University of Tasmania, TAS, Australia.
³ Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, VIC, Australia.
⁴ Faculty of Medicine, Nursing and Health Science, Monash University, Clayton, VIC, Australia.
⁵ Department of Ophthalmology, Guangdong Eye Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Southern Medical University, Guangzhou, China.
⁶ State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
⁷ Experimental Ophthalmology, The Hong Kong Polytechnic University, Hong Kong, China.

Abstract

Background: Limited knowledge exists regarding the association between dementia incidence and vitamin D insufficiency/deficiency across seasons.

Objective: This study aimed to evaluate the impact of seasonal serum vitamin D (25(OH)D) levels on dementia and its subtypes, considering potential modifiers.

Methods: We analyzed 193,003 individuals aged 60-73 at baseline (2006-2010) from the UK Biobank cohort, with follow-up until 2018. 25(OH)D were measured at baseline, and incident dementia cases were identified through hospital records, death certificates, and self-reports.

Results: Out of 1,874 documented all-cause dementia cases, the median follow-up duration was 8.9 years. Linear and nonlinear associations between 25(OH)D and dementia incidence across seasons were observed. In multivariable-adjusted analysis, 25(OH)D deficiency was associated with a 1.5-fold (95% CIs: 1.2-2.0), 2.2-fold (1.5-3.0), 2.0-fold (1.5-2.7), and 1.7-fold (1.3-2.3) increased incidence of all-cause dementia in spring, summer, autumn, and winter, respectively. Adjusting for seasonal variations, 25(OH)D insufficiency and deficiency were associated with a 1.3-fold (1.1-1.4) and 1.8-fold (1.6-2.2) increased dementia incidence, respectively. This association remained significant across subgroups, including baseline age, gender, and education levels. Furthermore, 25(OH)D deficiency was associated with a 1.4-fold (1.1-1.8) and 1.5-fold (1.1-2.0) higher incidence of Alzheimer's disease and vascular dementia, respectively. These associations remained significant across all subgroups.

Conclusions: 25(OH)D deficiency is associated with an increased incidence of dementia and its subtypes throughout the year.

Keywords: Alzheimer’s disease; dementia; moderation analysis; season; vitamin D.