Data indicate that psoriasis affects 2% to 3% of the world population. Although research suggests that psoriasis and dementia are both complex diseases with multifactorial pathogenesis that share common inflammatory characteristics, evidence is limited on whether psoriasis impacts cognitive impairment and risk for dementia. “My colleagues and I observed patients with psoriasis and their caretakers reporting symptoms of cognitive impairment at home, and they asked us if psoriasis could be associated with the decline in cognitive ability that these patients were experiencing,” explains Hsi Yen, MD, MPH. Literature on the subject has produced mixed results, with no analysis of the most recent evidence. Dr. Yen and colleagues sought to fill this gap, while also determining if they could better help their patients.

The researchers conducted a systematic review of case-control, cross‐sectional, and cohort studies to determine the association of psoriasis with dementia and cognitive impairment for a study published in The British Journal of Dermatology. The study team searched PubMed and Embase to identify 11 studies evaluating more than 16,500 patients with psoriasis and more than 45,000 control patients for risk of dementia or cognitive impairment.

Key Findings

The study team found that nine of the 11 studies concluded that there was a positive association between psoriasis and dementia or mild cognitive impairment (Table). “We think the jury is still out on whether better control of psoriasis or use of systemic anti-psoriatic treatment would help reduce the risk of dementia,” notes Dr. Yen. “There is a definite need for long-term randomized studies to reach solid conclusions.”

The data from the 11 analyzed study indicate, overall, that dementia and mild cognitive impairment risk could be higher in moderate to severe cases of psoriasis. One analyzed study that used systemic treatment as a proxy to see if dementia risk differed by psoriasis severity found a decrease in the risk of dementia with longer systemic antipsoriatic treatment. “Our team hypothesized that the increased use of antihypertensive medication and anti-psoriatics could have a protective effect against dementia. However, the evidence in the literature is still inconclusive,” adds Dr. Yen.

Two of the analyzed studies suggested that patients with psoriasis, especially those aged 60 or older reporting symptoms of cognitive decline, complete brief cognitive screening tests to detect early cognitive changes. The study team did not find specific data to validate this suggestion, but believe that because mild cognitive impairment and dementia are such serious healthcare burdens that the recommendation could be beneficial for both patients and physicians.

When asked about the study “Psoriasis Is Not a Risk Factor for Dementia: A 12-year Nationwide Population-based Cohort Study,” published in the Archives of Dermatological Research, Dr. Yen said, “Interestingly, while the number of psoriasis patients with dementia per 10,000 person-years was higher than in controls, the hazard ratio did not reach statistical significance and instead showed a null association. The same was true with the multivariate analysis, which demonstrated a null association after adjusting for other potential confounders. We saw similar findings in a large population-based study we analyzed. One similarity between these two cohorts is that they consist mainly of patients with milder psoriasis.”

More to Come

“There is a great need for more studies to assess dementia risk via subgroup analysis based on psoriasis severity,” says Dr. Yen. “Further research could determine how the risk differs between well-controlled and poorly controlled psoriasis. There is currently insufficient evidence with regard to the use of systemic anti-psoriatic treatment for reducing dementia risk; we believe a corollary might be drawn from rheumatoid arthritis, where conventional treatments for treating inflammatory rheumatic disease have been repurposed for treating dementia. It would be interesting to see if a newer anti-psoriatic biologic treatment can be used to drive novel dementia treatment studies.”