Background: Dementia is a syndrome that involves the deterioration of several higher mental functions in advanced age, and psoriasis is an autoimmune disease characterized by skin plaque. Epidemiological studies have indicated an association between dementia and psoriasis; however, to date, no studies in Asia have reported this association. Objective: This study used a population-based medical dataset to explore the association between previously diagnosed psoriasis and dementia in Taiwan. Methods: Using the Taiwan Longitudinal Health Insurance Database 2000, we identified 7118 individuals with a diagnosis of dementia; a further 21,354 sex- and aged-matched individuals were randomly extracted as controls. Patients with bullous pemphigoid, which is characterized by inflammatory phenomena similar to that evident in psoriasis, were chosen as a control group. Conditional logistic regression was performed to evaluate the association between dementia and prior psoriasis or bullous pemphigoid among the sampled patients. Results: Of the 28,472 individuals, 2.2, 3.0, and 1.5% of the total, case, and control groups, respectively, had been diagnosed with psoriasis. After adjustments were made for patients’ monthly income, region, urbanization level, diabetes, hyperlipidemia, hypertension, and coronary heart disease, the odds ratio (OR) of diagnosed psoriasis for the case group was 1.46 (95% confidence interval [CI] 1.23–1.73; p < 0.001) compared with the control group. The ORs of a previous psoriasis diagnosis with arthritis and without arthritis in the case group were, respectively, 1.95 and 1.44 times (95% CI 1.03–3.89 and 1.21–1.72, respectively) those of the control group after adjustments for socioeconomic variables, diabetes, hyperlipidemia, hypertension, and coronary heart disease. However, no significant differences in prior bullous pemphigoid were observed between the dementia and control groups (0.5% and 0.4%, respectively). Conclusions: More patients with dementia had prior psoriasis than did patients in the control group. Additional research is required to confirm our results and clarify the relationship.
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