A retrospective cohort study published in the Journal of Ophthalmology, has concluded that people with age related macular degeneration have a higher risk of Alzheimer’s disease (AD) and Parkinson’s disease (PD). The research continues an ongoing effort to better understand the pathogenesis of the diseases, and whether treatment for one may protect against or perhaps exacerbate another.
The research continues an ongoing effort to better understand the pathogenesis of the diseases, and whether treatment for one may protect against or perhaps exacerbate another
The Korean study involved 308,340 participants aged 50 years or older from the Korean National Health Insurance Service – Health Screening Cohort. After excluding participants with AMD during 2002, participants were screened for AMD during 2003-2005 then followed up for AD and PD from 1 January 2006 until 31 December 2013.
Following analysis, the study authors concluded that patients with AMD do have a higher risk for AD and PD. This held true even among those with healthy lifestyle behaviours – i.e. people who had never smoked, did not consume alcohol and regularly exercised. They recommended AMD patients be closely monitored for possible subsequent development of AD or PD.
AMD and AD
Previous studies have reported varying results for a potential association between AMD and dementia or cognitive impairment. The Blue Mountains Eye Study in Australia, analysed 3,509 people 49 years or older from 1997 through 2000 and after multivariate adjustment for age, sex, stroke, smoking, hypertension, alcohol, and occupation, found a borderline significant association between late AMD and cognitive impairment and no significant association between early AMD and cognitive impairment. This study was limited by its cross sectional design and small numbers (just nine participants had late AMD and cognitive impairment, and 23 had early AMD and cognitive impairment).
A UK study published in JAMA Ophthalmology in 2014 found that the coexistence of AD and other dementia after AMD at the individual level “was no different from that expected by chance”.
An AMD cohort of 65,894 people, constructed from the English National Health Service, was analysed to determine whether individuals admitted to the hospital with AMD were significantly more or less likely to develop AD or dementia in the following years, as well as to assess whether people with AD or dementia were significantly more or less likely to be admitted to the hospital for AMD treatment in the years following diagnosis of dementia.
That study found that the risk of AD or dementia following AMD was not elevated and the likelihood of being admitted for AMD following AD or dementia was very low.
The authors reported that “these neurodegenerative conditions may share environmental risk factors and histopathologic features. However, considering AD and other dementia after AMD, their coexistence at the individual level is no different from that expected by chance. Our data also suggest that patients in England with dementia may be substantially less likely to receive AMD treatment. Further research is required to determine whether people with dementia receive appropriate investigation and treatment for AMD, as well as identify and address potential barriers.”
AMD and PD
The Korean findings with regard to AMD and PD did reflect those of previous studies, including one published in Journal of Current Ophthalmology in 2018.
This cohort study analysed the British Columbia (BC) Retinal Disease Database of 13,124 subjects from 2009 to 2013. Rates of PD in patients prior to diagnosis of nAMD were computed and compared to rates of patients newly diagnosed with PD after the diagnosis of nAMD.
The findings suggest that patients who are diagnosed with nAMD are at a significantly higher risk of developing PD later in life – the rate of PD prior to diagnosis of nAMD was 1.42 per 100,000 person-years whereas the rate of PD after nAMD diagnosis was 2.88/100,000 person-years.
The authors concluded, “the implications of our study suggest that nAMD may be a predictive factor for the onset of PD”. They wrote that more research would be needed to understand the pathomechanism between neovascular AMD and PD, and whether there is a causal relationship between the two.
References
- Choi S, Jahng WJ, Park SM, Jee D. Association of age-related macular degeneration on Alzheimer’s or Parkinson’s disease: a retrospective cohort study. Am J Ophthalmol. 2019 Nov 8. pii: S0002-9394(19)30531-8. doi: 10.1016/j.ajo.2019.11.001. [Epub ahead of print]
- Keenan, TDL, Goldacre, R, Goldacre, M. Associations between age-related macular degeneration, alzheimer Disease, and dementia. Record Linkage Study of Hospital Admissions. JAMA Ophthalmol. 2014;132(1):63-68. doi:10.1001/jamaophthalmol.2013.5696
- Mahyar Etminan,M Samii, A and Hec B. Risk of Parkinson’s disease in patients with neovascular age-related macular degeneration. J Curr Ophthalmol. 2018 Dec; 30(4): 365–367.
