Abstract Dietary magnesium (Mg) is a potentially modifiable factor in preventing dementia, but current evidence supporting this remains insufficient and inconclusive. This study aimed to determine whether dietary Mg is associated with the risk of dementia among middle-aged and older people. Participants of this 8-year cohort study were 13,032 community-dwelling individuals aged 40–74 years. Dietary data were collected using a validated food frequency questionnaire in 2011–2013. Mg intake was adjusted for energy intake using the residual method. The outcome was newly diagnosed dementia determined using Japan’s long-term care insurance database. Covariates included demographic characteristics, body size, lifestyles, and disease histories. Cox proportional hazard models were used to determine adjusted hazard ratios (HRs). The mean age of participants was 59.0 years. Dementia occurred in 148 males and 138 females. Lower quartiles of energy-adjusted Mg intake were associated with a higher risk of dementia ( P for trend = 0.0410) in males, with the lowest quartile (Q1) having an elevated risk of dementia (HR = 1.73, 95% CI:1.07–2.83) compared to the highest quartile (Q4, reference); however, this association was not found in females. In a subgroup analysis by disease history in males, the HR of Q1 was attenuated in both subgroups; HR was 1.52 (95% CI:0.74–3.11) in those with a disease history and 1.40 (95% CI:0.73–2.69) in those without. In conclusion, low dietary Mg intake is associated with increased dementia risk in middle-aged and older Japanese males. However, this association may be partly attributable to underlying disease history.
Bulycheva et al. (2026) studied this question.