Dementia is not a specific disease, it is a general term for a reduced ability to remember, think, or make decisions that interferes with everyday activities. Psoriasis is a skin condition where an overactive immune system causes inflammation and speeds up skin growth causing flaky skin patches that form scales. Existing research suggests dementia might be more common in people with psoriasis. But other research suggests people with psoriasis are not at any greater risk of dementia than others.
There is evidence that people with inflammation in the body during midlife are more likely to develop dementia. The inflammation of psoriasis could therefore explain a link between psoriasis and dementia. If so, it is possible that effective psoriasis treatment could delay or prevent dementia. Recently, new and effective targeted drugs have been introduced to manage psoriasis. However, currently these drugs are only recommended for severe psoriasis. If our study indicates psoriasis is linked to dementia, this could provide an argument for using these new drugs for people with milder psoriasis to reduce their dementia risk.
Our study will follow very large numbers of people with and without psoriasis over time to see whether they develop dementia. We will determine whether there is a link between psoriasis and dementia, after accounting for other differences between people with and without psoriasis. For example, it may be that people with psoriasis are more likely to experience other illnesses that might explain why they have more dementia rather than psoriasis itself.
Our overall aim is to explore the relationship between psoriasis and dementia (all-cause and dementia subtypes), through a matched cohort study.
Existing evidence of an association between psoriasis and dementia is limited and conflicting. Evidence of a link between psoriasis and dementia would: 1) offer further insights into the well-demonstrated association between inflammation and dementia; and 2) influence clinical practice by highlighting the importance of monitoring cognitive function in those with psoriasis and offering interventions/lifestyle advice to limit dementia risk. Psoriasis is relatively common (up to 2% of population), our findings could have substantial public health impact.
We will establish a matched cohort of adults aged ≥40 years with psoriasis (both incident and prevalent cases), and an age, sex, and GP-practice matched cohort of individuals without psoriasis during the same period (from 1997 to latest linked data available). Follow-up of people without psoriasis will start on the same date as that of their matched person with psoriasis (i.e., for those with psoriasis follow up starts on the latest of: first record of a psoriasis diagnosis, GP registration plus one year, study start, 40th birthday, or date practice met CPRD quality control standards).
We will use Cox regression (adjusted for potential confounders and accounting for matching) to estimate hazard ratios comparing the risk of dementia in those with and without psoriasis. Potential confounders considered will include: lifestyle factors (e.g., smoking, harmful alcohol use, body mass index), socioeconomic deprivation, ethnicity, and comorbidities (e.g., cardiovascular disease, cerebrovascular disease). We will construct minimally adjusted models including just the main exposure variable (psoriasis) and implicitly adjusted for matching variables and underlying timescale, followed by sequential models adjusting for other potential explanatory variables (such as comorbidities and lifestyle factors). In separate secondary analyses we will explore whether psoriasis severity and psoriatic arthropathy increases risk of dementia.
dementia; dementia subtypes (Alzheimer’s disease, vascular dementia, mixed dementia, other)
Charlotte Warren-Gash - Chief Investigator - London School of Hygiene & Tropical Medicine ( LSHTM )
Kathryn Mansfield - Corresponding Applicant - London School of Hygiene & Tropical Medicine ( LSHTM )
Catherine Smith - Collaborator - King's College London (KCL)
Julian Matthewman - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
Katrina Abuabara - Collaborator - University Of California, San Francisco
Krishnan Bhaskaran - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
Sharon Cadogan - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
Sinead Langan - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
HES Admitted Patient Care;ONS Death Registration Data;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation