Dementia is a sickness defined by the decline of numerous higher mental processes in old age, while psoriasis is an inflammatory illness marked by skin plaque. Epidemiological studies have found a link between dementia and psoriasis; however, no research in Asia has found this link so far. For this study, researchers examined the relationship between previously diagnosed psoriasis and dementia in Taiwan using a population-based medical dataset.

They identified 7,118 individuals with dementia using the Taiwan Longitudinal Health Insurance Database 2000; a further 21,354 sex- and age-matched individuals were randomly selected as controls. As a control group, patients with bullous pemphigoid, which is characterized by inflammatory symptoms comparable to psoriasis, were chosen. In the studied individuals, conditional logistic regression was used to assess the relationship between dementia and previous psoriasis or bullous pemphigoid.

Psoriasis was identified in 2.2, 3.0, and 1.5% of the total, case, and control groups, respectively, of the 28,472 people studied. After adjusting for patients’ monthly income, geography, level of urbanization, diabetes, hyperlipidemia, hypertension, and coronary heart disease, the case group’s odds ratio (OR) of confirmed psoriasis was 1.46 (95% confidence interval [CI] 1.23–1.73; p < 0.001) compared to the control group. After adjusting for socioeconomic variables, diabetes, hyperlipidemia, hypertension, and coronary heart disease, the ORs of a previous psoriasis diagnosis with arthritis and without arthritis in the case group were 1.95 and 1.44 times (95% CI 1.03–3.89 and 1.21–1.72, respectively) those of the control group. However, there were no significant changes in preceding bullous pemphigoid between dementia and control groups (0.5% and 0.4%, respectively).