Related Experiment Video
Updated: Jan 15, 2026

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data
Published on: December 9, 2015
Association between plasma 25-hydroxyvitamin D concentration and incident disabling dementia risk in Japan: a
Yukai Lu1, Taiki Yamaji2, Nobufumi Yasuda3
1Division of Cohort Research, National Cancer Center Institute for Cancer Control, Tokyo, Japan.
Objectives:
Previous studies have suggested neuroprotective effects for vitamin D, but no conclusions have been reached. We aimed to investigate the association between plasma 25-hydroxyvitamin D (25[OH]D) concentration and incident disabling dementia among Japanese adults DESIGN: Case-cohort study SETTING: Within the Japan public health center-based prospective study PARTICIPANTS: 1858 disabling dementia cases and 2223 randomly selected subcohort participants from a base cohort of 14,184 participants MEASUREMENTS: Plasma 25(OH)D concentrations from samples collected in 1995-1998 were measured by enzyme immunoassay. Participants were divided into quartiles (Q1 ∼ Q4) based on sex- and season-specific distributions of 25(OH)D in subcohort participants. Incident disabling dementia was ascertained using long-term care insurance certifications for 2006-2016. Weighted cox proportional hazards model adjusted for confounders was used to calculate hazard ratios (HRs) and 95 % confidence intervals (95 %CIs) for all participants and for subgroups by sex and age (middle-aged: 45-64 y vs. older: 65-74 y) RESULTS: Compared to the lowest quartile, the highest quartile showed a higher risk of incident disabling dementia (HR: 1.29; 95 %CI: 1.01-1.66). This association did not differ by sex. Regarding subgroup analysis by age, only older adults in the highest quartile displayed an increased risk (HR:1.73; 95 %CI: 1.15-2.60), with no association observed among middle-aged participants CONCLUSION: This case-cohort study found no neuroprotective effect of 25(OH)D concentration against dementia risk among Japanese adults. Future studies with repeated 25(OH)D assessments and the ability to examine associations with specific dementia subtypes are needed to confirm our findings.
Related Concept Videos
Dementia
The progression of dementia is generally gradual....
Alzheimer's Disease: Overview
The clinical diagnosis of AD hinges on the presence of memory and other cognitive impairments. Biomarkers, such as changes in Aβ...
Hazard Ratio
For example, in a clinical trial...
Vitamins
Bias in Epidemiological Studies
Factors Affecting Illness
For instance, risk factors are connected to illness,...

