Midlife Vitamin D Levels Tied to Lower Tau Burden in Later Life

 Does this mean your competent? doctor will have EXACT supplement protocols for your use? Oh NO, NOTHING OF THE SORT!    

Midlife Vitamin D Levels Tied to Lower Tau Burden in Later Life

Higher levels of vitamin D in early midlife were associated with significantly lower levels of tau deposition 16 years later in adults without dementia.

Results of a prospective, community-based cohort of nearly 800 adults showed those with higher serum 25-hydroxyvitamin D [25(OH)D] levels measured at age 39 showed lower global and regional tau burden on follow-up brain imaging.

However, there was no such association between midlife vitamin D levels and subsequent amyloid burden, a hallmark of Alzheimer’s disease (AD). This suggests that vitamin D may be more closely linked to tau-related pathways in the earlier stages of the disease rather than amyloid accumulation.

“These results suggest that higher vitamin D levels in midlife may offer protection against developing these tau deposits in the brain and that low vitamin D levels could potentially be a risk factor that could be modified and treated to reduce the risk of dementia,” lead investigator Martin David Mulligan, MB BCh BAO, of the University of Galway in Galway, Ireland, said in a news release. “Of course, these results need to be further tested with additional studies.”

The study was published online on April 1 in Neurology Open Access.

Vitamin D and Preclinical AD Risk

Vitamin D deficiency has previously been associated with cognitive decline and an increased risk for dementia in older adults.

Prior meta-analyses have shown a dose-dependent relationship, with lower 25(OH)D levels associated with a higher AD risk.

However, most studies have focused on vitamin D levels measured later in life, which limits the ability to determine whether earlier exposure affects preclinical disease processes.

Advances in neuroimaging now allow for the detection of early AD changes in asymptomatic individuals. While both tau and amyloid deposition are key AD biomarkers, tau accumulation may appear earlier and is closely tied to neuronal injury and cognitive impairment.

For the current study, investigators wanted to determine whether vitamin D levels in early midlife are associated with subsequent tau and amyloid deposition in later years among individuals who are dementia free.

The study included 793 participants (mean age, 39.2 years; 53.8% female) from the Framingham Heart Study Generation 3 cohort who were dementia free at the time of imaging.

Serum 25(OH)D levels were measured between 2002 and 2005 in a subset of 435 participants, followed by PET imaging between 2016 and 2019. The average follow-up was 16 years.

Tau imaging data were available for 369 participants, whereas amyloid imaging data were available for 424 participants.

At baseline, the mean vitamin D level was 38 ± 15 ng/mL. Approximately 34% of participants had levels < 30 ng/mL, and only 5% reported vitamin D supplementation.

The investigators used flortaucipir PET to assess tau burden across both global cortical regions and regions particularly vulnerable in early AD, including the entorhinal cortex, parahippocampal gyrus, fusiform gyrus, amygdala, and temporal cortices.

The Pittsburgh compound-B PET was used to measure amyloid burden across multiple cortical regions as a comparative baseline against tau deposition.

The researchers conducted multivariable linear regression analyses to adjust for a range of potential confounders, including age, sex, time from blood draw to imaging, depression, season, smoking status, systolic blood pressure, antihypertensive use, diabetes, cardiovascular disease, and BMI.

Link to Tau but Not Amyloid

Results showed higher midlife vitamin D levels were independently linked to lower tau deposition on PET imaging 16 years later.

In fully adjusted models, higher 25(OH)D levels were associated with lower global tau burden (beta-coefficient, -0.022; 95% CI, -0.040 to -0.004; P = .010). A similar association was seen for tau deposition in regions most vulnerable to early AD (beta-coefficient, -0.023; 95% CI, -0.043 to -0.003; P = .016).

These associations remained after adjusting for age, sex, time to imaging, depressive symptoms, season, and cardiometabolic risk factors.

Across sensitivity analyses, the findings were consistent, including models excluding participants taking vitamin D supplements.

Notably, no significant relationship was observed between vitamin D levels and amyloid burden (beta-coefficient, 0.001; 95% CI, -0.024 to 0.024; P = .987).

In analyses that used a clinical cutoff < 30 ng/mL vs ≥ 30 ng/mL, no statistically significant associations with tau burden were found in fully adjusted models. This suggests a gradual dose-dependent relationship between vitamin D rather than a threshold effect.

There were no significant interactions observed by sex or apolipoprotein E epsilon 4 carrier status, which suggests that the association was consistent across key subgroups.

Study limitations included its reliance on a single measurement of vitamin D, potential residual confounding, and a predominantly White cohort, which may limit the generalizability of the findings, the investigators noted.

“Low vitamin D in midlife may represent a potentially modifiable target to mitigate the risk of neuroimaging signs of preclinical dementia,” the investigators wrote.

They cautioned, however, that the findings are observational and warrant further investigation. “Our results do require validation in other cohorts of younger to middle-aged adults with follow-up data on markers of preclinical dementia.”

Taken together, the researchers suggest vitamin D levels may be a potential window for early intervention but highlight the need for randomized clinical trials to determine whether vitamin D supplementation can meaningfully reduce tau accumulation or dementia risk.

The study was funded by the National Institutes of Health, National Institute on Aging, National Institute of Neurological Disorders and Stroke, Irish Research Council, and Health Research Board of Ireland. Disclosure information for study authors is available in the original study publication.