Seeing Dementia Burden Clearly
How does cataract removal affect the risk of developing dementia?
Geoffrey Potjewyd |
Diseases of aging tend not to be found in isolation; comorbidity is common, with one or more diseases exacerbating the progression of others in a damaging feedback loop of pathology. Vision loss and dementia have long been tied together in this way, with poor eyesight often leading to isolation and inactivity that can accelerate dementia. Dementia already places a huge burden on healthcare systems, as well as patients and their families – and this burden is only set to rise with an increasingly aged population.
So, is it possible to tackle the growing rates of dementia by targeting cataracts? In the first study to directly explore the relationship, researchers from the University of Washington, USA, found that cataract removal significantly reduces the risk of the patient developing dementia (1). The researchers analyzed a large pool of data from the Adult Changes in Thought study; specifically, the team assessed 3,038 participants, all of whom were over the age of 65 with glaucoma or cataracts before enrollment. Interestingly, glaucoma surgery did not appear to affect the risk of dementia developing, but those who had cataract surgery had close to a 30 percent lower risk, which persisted beyond 10 years.
The authors suggest that both increased quantity and quality of light may be behind the significant effect of cataract surgery on dementia risk. In particular, blue light, which acts on photosensitive retinal ganglion cells, is associated with positive measures in cognitive function and Alzheimer’s disease; the researchers note that the yellow hue of cataracts blocks blue light, possibly speeding the onset of dementia by inhibiting mental stimulation.
Healthy heart, healthy brain?
Another potential explanation (or co-conspirator) is the role of vascular health; visual impairment can be accompanied by a reduction in mobility and activity, which contributes towards poor vascular health – a major risk factor for dementia onset and progression. The removal of cataracts and the recovery of vision may enable more active and healthy lifestyles, increasing vascular health and thus reducing dementia risk.
The researchers admit that further research is needed to determine the mechanism of action. But, whatever the reason, their work provides another reason why cataract surgery is so important – if further justification were ever needed.
- CS Lee et al., JAMA Intern Med, e216990 (2021). PMID: 34870676.