An association between cataracts and development of dementia

I remember a number of years back at a lecture hearing about a study that reported a significant reduction in the risk of a fall if a patient had cataract surgery. This study reminds me of that. Association Between Cataract Extraction and Development of Dementia published in the December 2021 issue of JAMA Internal Medicine found a reduction of about 30% in the development of all-cause dementia if patients had cataract surgery.

They studied over 3000 patients 65 years old and older who did not have a diagnosis of dementia but did have a diagnosis of cataracts at the start of the study.

Based on 23 554 person-years of follow-up, cataract extraction was associated with significantly reduced risk (hazard ratio, 0.71; 95% CI, 0.62-0.83; P < .001) of dementia compared with participants without surgery after controlling for years of education, self-reported White race, and smoking history and stratifying by apolipoprotein E genotype, sex, and age group at cataract diagnosis.

They seemed to solve all the potential confounding issues with working with an older population. (My next post is going to be about the APOE genotype. It has nothing to do with the eyes, but it’s fascinating.)

Their hypotheses were interesting. The visual impairment might accelerate degeneration as the visual cortex goes through a degenerative process with vision loss. The brain may be under significant stress trying to compensate for the loss of vision accelerating the decline.

My favorite brings up ipRGCs which I wrote about before. (It also reminds me I never got around to writing the follow-up article on that. Add it to the list.)

Lower risk for developing dementia following cataract extraction may also be associated with increased quantity and quality of light. Intrinsically photosensitive retinal ganglion cells (ipRGCs), which are exquisitely sensitive to short-wavelength (blue) light, have been shown to be associated with cognitive function, circadian rhythm, and AD.

They used patients having glaucoma surgery as what they called a “negative control” and found no significant difference in their development of dementia. Going back to that previous paper, though, glaucoma is thought to damage ipRGCs as well. Surgical patients would be more severe glaucoma patients which has an association with cognitive decline. 🤔

There is definitely some kind of connection with ocular input and cognitive decline. More impetus to make sure our patients have maximum vision no matter the age.

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