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2nd May 2022
Having atopic eczema in older life increases the risk for developing Alzheimer’s disease, according to a study by researchers from UC Berkeley School of Public Health, Berkeley, California, USA.
Alzheimer’s disease (AD) is a neurodegenerative disorder which is progressive and characterised clinically by cognitive decline and physiologically by the presence of two core pathologies; amyloid β plaques (Aβ) and neurofibrillary tangles (NFTs). AD is the most common form of dementia which, according to the World Health Organization (WHO), affected some 55 million people in 2021 with AD accounting for 60-70% of all dementia cases.
Among those with AD, there is a sustained inflammatory response in the brain which is thought to represent a persistent immune response and a factor exacerbating both Aβ and NFTs. Moreover, there is emerging evidence that peripheral inflammation is an early event in the pathogenesis of AD. Atopy, which manifests as either allergic rhinitis, atopic eczema or asthma, represents a set of peripheral inflammatory diseases that have been found to be associated with a modestly increased risk of AD and dementia. To date, only one study has suggested that atopic eczema may be an independent risk factor for new-onset dementia and in particular, AD.
For the present analysis, the team set out to determine whether active atopic eczema among older adults was associated with incident AD and wondered if the strength of this association was dependent upon atopic eczema disease severity. They performed a longitudinal cohort study of patient data collected from the Health Improvement Network, which provides information on a representative sample of patients from UK general practitioners. For their analysis, the researchers included patients aged 60 to 100 years of age without a prior diagnosis of AD or dementia and for whom the primary exposure was the presence of active atopic eczema and for which at least two prescriptions for treatment of the condition had been issued. The severity of atopic eczema during follow-up was categorised as either mild moderate or severe and the primary outcome was a new diagnosis of dementia during the period of follow-up. The researchers also examined the reported disease codes for dementia and excluded those where the condition was drug- or alcohol-related or due to trauma or a rarer form (e.g. Huntington’s). The analysis was adjusted for potential confounders including gender, smoking, alcohol status, etc.
Atopic eczema and risk of Alzheimer’s disease
In a total of 1,767,667 individuals aged 60 to 100 years of age at baseline, 57,263 were diagnosed with dementia over mean of 6.8 years of follow-up. The median age of patients with a dementia diagnosis was 82 years, of whom, two-thirds (65%) were female.
Atopic eczema was diagnosed in 12% of the whole cohort and using mild disease severity as the default, 44% had moderate and 5% disease severity over the follow-up period.
Considering AD, the analysis showed that after adjustment for confounders, mild atopic eczema was associated with a 22% higher risk of AD (HR = 1.22) and this risk was higher still for those with moderate (HR = 1.37) and severe (HR = 1.52) disease.
With AD being the most common form of dementia, the researchers also examined the link between atopic eczema and the risk of developing dementia. The incidence of dementia was 57/10,000 person-years among those with atopic eczema compared to 44/10,000 person-years among those without the condition. Overall, patients with atopic eczema had a 27% higher risk for dementia after adjustment for potential confounders (hazard ratio, HR = 1.27, 95% CI 1.23 – 1.30). Further adjustment for co-morbidities slighted attenuated this risk but it remained significant (HR = 1.19, 95% CI 1.16 – 1.22).
The authors concluded that given the increased risk of AD among adults with atopic eczema, clinicians consider the impact of screening those with eczema for signs of cognitive impairment.
Magyari A et al. Adult atopic eczema and the risk of dementia: A population-based cohort study J Am Acad Dermatol 2022