Everwood Reserve | Resident Wellness

Vitamin D deficiency is rampant in older adults and emerging science links it to accelerated cognitive decline. Here is what families and care teams need to know.

At Everwood Reserve, our approach to memory care and assisted living begins with a foundational belief: prevention starts long before a diagnosis. One of the most underappreciated tools in that effort, sitting quietly in your bloodwork, is vitamin D.

Often dismissed as merely a “bone vitamin,” vitamin D is increasingly recognized as a powerful neuroactive hormone with far-reaching effects on brain health, immune function, mood regulation, and longevity. And the population most at risk for deficiency? Older adults, the very people we serve every day.

PART ONE: WHY OLDER ADULTS ARE RUNNING LOW

Vitamin D deficiency is not a fringe concern. Research consistently shows it affects anywhere from 40 to 70 percent of older adults globally, with the highest rates found among nursing home residents and those with multiple chronic conditions. The reasons are multifactorial.

As we age, the skin’s capacity to synthesize vitamin D from sunlight declines significantly. Reduced time outdoors, decreased dietary intake, impaired kidney and liver conversion, and common medications all compound the problem. And in sunbelt states like Texas, where many assume sun exposure is ample, indoor living habits and sunscreen use often tell a different story.

Vitamin D deficiency has been linked to cardiovascular disease, compromised immunity, depression, increased fall risk, bone fragility, and critically, neurodegenerative disorders. These are not independent concerns. In older adults, they tend to travel together.

“More than half of adults over 50 exhibit vitamin D concentrations below optimal thresholds and nearly half of those affected are not taking any supplement at all.” — English Longitudinal Study of Ageing

PART TWO: VITAMIN D AND THE BRAIN: DEEPER THAN WE THOUGHT

Decades of research assumed vitamin D’s role in the brain was indirect, supporting vascular health, reducing inflammation, perhaps lifting mood. But the science has grown far more specific, and far more compelling.

Vitamin D receptors (VDRs) are distributed widely throughout the brain, in the hippocampus, cortex, cerebellum, and substantia nigra. The brain does not just respond to vitamin D; it actively converts and uses it locally. Astrocytes, the brain’s support cells, express VDRs that when activated initiate protective gene transcription pathways.

What does activated vitamin D actually do in the brain? Current research points to several mechanisms working in parallel:

Neuroinflammation control

Vitamin D suppresses pro-inflammatory cytokines and microglial activation, a central driver of age-related cognitive decline and Alzheimer’s pathology.

Amyloid-beta clearance

Active vitamin D promotes phagocytosis and clearance of amyloid-beta plaques, a hallmark of Alzheimer’s disease, and reduces their oligomeric formation.

Tau hyperphosphorylation

Vitamin D reduces age-related tau hyperphosphorylation, a process that destabilizes neuronal structure and contributes to neurofibrillary tangles.

Neurogenesis and synapses

Vitamin D upregulates proteins required for new synapse formation and supports neurogenesis, particularly in the hippocampus, the seat of memory.

Beyond these structural effects, vitamin D regulates the expression of key neurotransmitters including acetylcholine, dopamine, serotonin, and GABA. It also supports nerve growth factor (NGF) production, which promotes the survival of hippocampal and cortical neurons. This is a hormone the brain is clearly designed to use, and when it is absent, the consequences accumulate quietly over years.

PART THREE: WHAT THE RESEARCH SHOWS ABOUT DEMENTIA RISK

A major 2025 meta-analysis published in Frontiers in Neurology, synthesizing 22 studies and over 53,000 participants, found that individuals with the lowest vitamin D levels carried a 49 percent higher relative risk of developing dementia compared to those with the highest levels. The relationship demonstrated a dose-response pattern. As vitamin D levels declined, dementia risk climbed.

Separately, a landmark study published in April 2026 in Neurology followed 793 adults from midlife, average age 39, and measured their vitamin D levels at baseline. Years later, those with higher midlife vitamin D had measurably lower deposits of tau protein in the brain. Tau accumulation is one of the earliest detectable markers of Alzheimer’s pathology, suggesting vitamin D’s protective window extends decades before any cognitive symptoms appear.

“Higher vitamin D levels in midlife may offer protection against developing tau deposits in the brain, with low vitamin D potentially setting the stage for future cognitive risk.” — Neurology, April 2026

It is worth being honest about the limits of the evidence: some supplementation trials in already-sufficient populations have not shown dramatic reductions in incident dementia. A 2025 Finnish trial found no significant benefit from supplementation in adults who were not deficient at baseline. This nuance matters. The protective signal appears strongest in those correcting an actual deficiency, not those who are already replete. The takeaway is not to take more vitamin D regardless, but rather to identify and correct deficiency, particularly in high-risk populations.

PART FOUR: GENERAL HEALTH BENEFITS BEYOND THE BRAIN

Even setting aside cognitive health, the systemic benefits of adequate vitamin D in older adults are well established.

Bone and muscle health

Vitamin D is essential for calcium absorption and bone mineralization. Deficiency accelerates bone loss and increases fracture risk, and fall-related fractures remain one of the leading causes of morbidity and loss of independence in seniors.

Immune function

Vitamin D acts as an immunomodulatory hormone, regulating both innate and adaptive immune responses. Deficiency is associated with increased susceptibility to respiratory infections, and those with lower levels have been shown to experience more severe illness outcomes.

Mood and depression

Low vitamin D is consistently associated with depressive symptoms in older adults. Given the high rates of depression in assisted living settings and the overlap between depression and cognitive decline, this represents a meaningful and modifiable target.

Cardiovascular and metabolic health

Emerging evidence links adequate vitamin D to better blood pressure regulation, reduced diabetes risk, and lower rates of certain cancers, all conditions that commonly overlap in the populations we care for.

PART FIVE: WHY THIS IS PERSONAL TO ME

I take 5,000 IU of vitamin D3 daily, with a meal, since it’s best absorbed as a fat soluble supplement. My reasons are not purely clinical. I train with weights four to five days per week and bone density, muscle function, and long-term skeletal integrity are things I think about actively, not just in the context of patient care but in my own life. Vitamin D is a foundational part of it all.

I also carry what I have learned into my family. My mother is in her 60s, and as a caucasian female she carries a disproportionately elevated risk for osteoporosis. I put her on a protocol that includes 5,000 IU of vitamin D3 paired with K2, which works synergistically to direct calcium to the bones rather than allowing it to deposit in soft tissue. That combination, alongside a structured resistance training program I recommended specifically for her, is the kind of proactive, whole-person approach I believe in and that we bring to Everwood Reserve.

My interest in vitamin D did not begin in a lecture hall. It sharpened significantly during COVID-19, when the data on outcomes and vitamin D status became too consistent to ignore. People who were deficient had significantly worse outcomes. That observation was startling and only reinforced my interest and belief in vitamin D3.

This is the lens through which we think about resident wellness at Everwood Reserve. Not reactive, not minimal. Curious, evidence-informed, and individualized care at it’s core.

THE EVERWOOD RESERVE COMMITMENT

We built Everwood Reserve around a simple conviction: that excellence in residential care means going beyond the basics of medication management and ADL support. It means attending to the nutritional, cognitive, and physiological inputs that determine whether residents thrive, not merely survive. Vitamin D is one piece of that picture. But it is a piece too often overlooked, in homes and clinics alike. Every resident is an individual and their needs should be treated as such, not another number in a nursing home.

Joseph Rasberry, PA-C

REFERENCES

Huang Y, Chen Y, Wu Y, Dai X, Feng J, Li X. Association of vitamin D with risk of dementia: a dose-response meta-analysis of observational studies. Front Neurol. 2025;16:1649841. doi:10.3389/fneur.2025.1649841

Liu Y, Zhong Z, Xie J, Ni B, Wu Y. Neuroprotective roles of vitamin D: bridging the gap between mechanisms and clinical applications in cognitive decline. Neurology. Published April 2026. doi:10.1212/WNL

Lönnroos E, Ylilauri M, Lamberg-Allardt C, et al. Effect of vitamin D3 supplementation on the incidence of diagnosed dementia among healthy older adults: the Finnish Vitamin D Trial. J Gerontol A Biol Sci Med Sci. 2025;80(7):glaf077. doi:10.1093/gerona/glaf077

Stafford M, Cooper R, Cadar D, et al. The prevalence and determinants of vitamin D status in community-dwelling older adults: results from the English Longitudinal Study of Ageing (ELSA). Nutrients. 2019;11(6):1253. doi:10.3390/nu11061253

Salari N, Hassanabadi M, Khaleghi AA, Mohammadi M. The global prevalence of vitamin D deficiency in the elderly: a meta-analysis. Indian J Orthop. 2024;58(3):223-230. doi:10.1007/s43465-023-01089-w

Laktionova KE, Turna AA, Smirnova LM. Vitamin D deficiency remains alarmingly high in seniors. Nutraingredients. January 12, 2024.

di Filippo L, Terenzi U, Giustina A. Vitamin D in the elderly: the phil-rouge in preventing bone, muscle and adipose deterioration. Arch Endocrinol Metab. 2025.

Amrein K, Scherkl M, Hoffmann M, et al. Vitamin D deficiency. StatPearls. Updated February 2025.