Scientists from Huazhong University of Science and Technology have found that higher levels of vitamin D in the body are associated with a lower risk of developing dementia among people with type 2 diabetes.
The study, led by Tingting Geng and published in PLOS Medicine, adds to growing evidence that vitamin D may play an important role in protecting brain health, especially in populations already at higher risk of cognitive decline.
Type 2 diabetes is a chronic condition that affects how the body processes glucose, or blood sugar.
It occurs when the body either does not produce enough insulin or becomes resistant to its effects.
Common symptoms include increased thirst, frequent urination, fatigue, hunger, and blurred vision, although some people may have no noticeable symptoms.
Over time, poorly controlled diabetes can damage blood vessels and nerves throughout the body, including those in the brain.
People with type 2 diabetes have consistently been shown to face a higher risk of developing cognitive problems such as mild cognitive impairment, Alzheimer’s disease, vascular dementia, and general cognitive decline.
These conditions involve a gradual loss of memory, reasoning, and the ability to carry out everyday tasks.
Vitamin D is a fat-soluble vitamin best known for its role in helping the body absorb and retain calcium and phosphorus, which are essential for healthy bones and teeth. However, it also has other important functions.
Laboratory and clinical studies suggest that vitamin D can help regulate immune responses, reduce inflammation, and protect cells against damage.
These properties have led researchers to investigate its potential role in preventing chronic diseases, including cancer and neurodegenerative disorders.
Several previous studies have linked vitamin D status to dementia risk in the general population, but until recently it was unclear whether this relationship also applied to people with type 2 diabetes.
To explore this question, the research team analysed data from more than 13,000 adults aged over 60 who had type 2 diabetes but did not have dementia at the time of recruitment into the UK Biobank between 2006 and 2010.
Over an average follow-up period of 8.5 years, 283 participants developed dementia. These cases included 101 instances of Alzheimer’s disease and 97 cases of vascular dementia.
When the researchers analysed vitamin D levels in the participants’ blood, they found a clear association between higher vitamin D levels and a lower risk of developing all-cause dementia, Alzheimer’s disease, and vascular dementia.
In other words, participants with higher serum vitamin D concentrations were significantly less likely to be diagnosed with dementia during the follow-up period.
The researchers concluded that maintaining adequate or higher vitamin D levels may offer a protective effect against cognitive decline in people living with type 2 diabetes.
If confirmed by future research, these findings could contribute to new dementia prevention strategies focused on routine screening and management of vitamin D levels in people with diabetes, alongside other lifestyle and medical interventions.
The researchers also acknowledged a key limitation of the study. Dementia cases were identified using electronic health records, which means some cases may not have been recorded or diagnosed, possibly leading to an underestimation of the true number of cases.
Despite this limitation, the study provides important insight into a potentially modifiable risk factor for dementia in a high-risk population. Ensuring adequate vitamin D levels—through safe sun exposure, diet, or supplementation under medical guidance—may become an important part of comprehensive brain health strategies for people with type 2 diabetes.
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