Bullous pemphigoid and psoriasis may be associated with an increased risk for Alzheimer disease, and skin cancer may have a protective effect, according to study findings published in Clinical, Cosmetic and Investigational Dermatology.

Researchers conducted a review of studies regarding the relationship between Alzheimer disease and bullous pemphigoid, hidradenitis suppurativa, psoriasis, skin cancer, and cutaneous amyloidosis.

Some studies have reported an association between dementia and bullous pemphigoid, with a risk ratio (RR) ranging from 2.2 to 4.8. The investigators cited a Finnish study in 2016 that found an RR for bullous pemphigoid of 2.6 in patients with Alzheimer disease and an RR of 3.6 in patients with vascular dementia. A separate multi-centered, case-control study found decreased cognitive capability and a higher risk for cognitive impairment in patients with bullous pemphigoid and that these patients were more likely to develop dementia.


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Several studies have shown an increased risk for dementia in patients with psoriasis, with an RR ranging from 1.10 to 1.25. Evidence has also shown that the risk for psoriasis increases in patients with dementia. A meta-analysis the researchers included found that the risk for vascular dementia and nonvascular dementia among patients with psoriasis was higher than in patients without psoriasis (RR, 1.41; RR, 1.13, respectively).

A population-based study of 1102 adults found a lower risk for Alzheimer disease (hazard ratio, 0.50) in patients with nonmelanoma skin cancer (NMSC) compared with those without NMSC. Also, a large, single-centered study found a significantly decreased risk for Alzheimer disease in malignant melanoma patients and NMSC patients.

The investigators found unclear evidence for any potential relationship between Alzheimer disease and hidradenitis suppurativa and cutaneous amyloidosis.

The researchers noted that their review included only 5 skin diseases, which were the 5 most-discussed skin diseases in the literature. Also, evidence is lacking for the mechanisms of the association between Alzheimer disease and skin diseases.

“Although we still cannot say that there exists a correlation between Alzheimer’s disease and skin diseases based on current evidence, this review may have some clinical applications,” the study authors concluded. “Neurologists, dermatologists, and general practitioners should be aware of the relationship between Alzheimer disease and skin diseases.”

Reference

Zhang H, Zhang D, Tang K, Sun Q. The relationship between Alzheimer’s disease and skin diseases: a review. Clin Cosmet Investig Dermatol. 2021;14:1551-1560. doi: 10.2147/CCID.S322530