Study Suggests Those with Psoriasis Likely Not at Greater Risk for Alzheimer’s

Long-term risk of developing all-cause dementia and vascular dementia is slightly higher among individuals with psoriasis, new findings suggest, though risk of Alzheimer's dementia was not higher for those with psoriasis.1

Such findings represent the conclusion of a new analysis by a team of investigators led by Julian Matthewman, PhD, MSc. Matthewman works in the department of non-communicable disease epidemiology at the London School of Hygiene and Tropical Medicine.

The investigators noted that recent analyses into associations between chronic inflammatory conditions like psoriasis and risk of Alzheimer's disease and other dementias had previously led to conflicting results.2,3 Matthewman et al. expressed that an improved understanding of any links between psoriasis and dementia in research evaluating causality could be beneficial.

“Therefore, our study investigated the association between psoriasis and all-cause dementia risk in a large population-based cohort using routinely collected electronic health records from English primary and secondary care,” Matthewman and colleagues wrote. “We specifically investigated whether increasing psoriasis severity affected dementia risk.”1

Background and Design Details

The study included 360,014 individuals with psoriasis and 1,799,617 controls without the condition. The investigative team matched their study participants by sex, by primary care practice, and by age, assessing records spanning April 1997 - March 2021 that were drawn from the Clinical Practice Research Datalink (CPRD) Aurum.

This database contains primary care practice electronic records of patients located in England, with over 20% of the UK population and other linked datasets included. Some of the aforementioned datasets included Office for National Statistics (ONS) mortality records, the Index of Multiple Deprivation, and the Hospital Episode Statistics (HES) for NHS-funded hospital admissions.

The research team’s analysis followed subjects with diagnoses of psoriasis, defining participants’ index dates as the latest of several factors: the study start date (April 1, 1997), a single year post-practice registration, the first recorded psoriasis diagnostic code, or the participant’s 40th birthday.

Those subjects deemed to be eligible were required to be at least 40 years old, to be registered with Aurum practices in the investigators’ period of study, to have hospital admission and death data, and to have a minimum of 12 months of registration prior to trial entry to ensure accurate health information at the point of baseline. The investigative team compared risk of developing dementia between participants in the study with psoriasis and without psoriasis, implementing stratified Cox regression analyses.

Findings on Dementia Risk

Overall, the investigators identified an absolute rate difference of 24 cases per 100,000 person-years among the participants, suggesting a slightly raised risk of all-cause dementia among individuals given a diagnosis of psoriasis (adjusted hazard ratio [aHR] 1.06, 95% CI 1.04–1.08).

This link was noted by the research team as having strengthened slightly with longer durations since subjects’ psoriasis diagnosis. This was expressed through the aHR of 0.99 (95% CI 0.96–1.03) within the initial 5 years rise to 1.20 (95% CI 1.05–1.37) following a period of 20–25 years.

The team further noted that risk of developing vascular dementia was significantly increased (aHR 1.10, 95% CI 1.06–1.14) compared to risk of Alzheimer's-related dementia (aHR 1.03, 95% CI 1.00–1.06). Associations were shown by the investigators to be more pronounced in patients reporting more severe cases of psoriasis.

Specifically, the researchers highlighted hazard ratios of 1.32 (95% CI 1.25–1.39) for all-cause dementia, 1.58 (95% CI 1.44–1.74) for those with vascular dementia, and 1.11 (95% CI 1.02–1.21) for those with Alzheimer’s dementia. These data underscore the nuanced connection observed between severity of the skin disease and risk of dementia, highlighting vascular contributions to cognitive decline among such individuals.

“Reassuringly, our study suggests it is unlikely people with psoriasis are at increased risk of Alzheimer's disease compared to the general population (or at least any increased risk is likely to be very small),” they wrote. “While the finding of increased risk of all-cause dementia was unlikely due to chance, the increase in risk was again very small and potentially not clinically important, or could be explained through residual bias or confounding.”1

References

1. Matthewman, J., Mansfield, K.E., Cadogan, S.L., Abuabara, K., Smith, C., Bhaskaran, K., Langan, S.M. and Warren-Gash, C. (2025), Psoriasis and dementia: A population-based matched cohort study of adults in England. Ann Clin Transl Neurol. https://doi.org/10.1002/acn3.52283.
2. Huang J, Su B, Karhunen V, et al. Inflammatory diseases, inflammatory biomarkers, and Alzheimer disease. Neurology. 2023; 100(6): e568-e581.
3. Charoenngam N, Rittiphairoj T, Ponvilawan B, Ungprasert P. Patients with psoriasis have a higher risk of dementia: a systematic review and meta-analysis. Indian J Dermatol Venereol Leprol. 2021; 87(3): 364-370.