Originally published by 2 Minute Medicine^® (view original article). Reused on AccessMedicine with permission.

1. A cohort study of 3038 participants found that cataract extraction was associated with a significantly lower risk of developing dementia compared to those who had not had cataract surgery.

Evidence Rating Level: 2 (Good)

Study Rundown:

Dementia is a common neurodegenerative disease which primarily affects older adults. A primary contributor to vision loss in older adults is cataracts; fortunately, cataract surgery is relatively common in North America and patients rarely progress to total blindness, although visual impairment remains common. It is believed that reducing the impacts of sensory loss in elderly patients may be protective against the development of dementia. The present study hypothesized that cataract surgery may lower the risk of developing dementia later in life amongst the general population. This longitudinal, prospective cohort study began enrolling patients in 1994; adults aged 65 and older who had received a diagnosis of cataracts before the onset of dementia were included in this analysis. A total of 3,038 participants were included, with 1,382 (45.5%) receiving cataract surgery and 1656 (54.5%) not receiving surgery. The mean age at diagnosis of cataracts was 74.4 years. The total follow-up period was 23,554 person-years; during this time, 853 cases of dementia and 709 cases of Alzheimer’s dementia were diagnosed. Cataract extraction surgery was significantly associated with a lower risk of dementia diagnosis. This protective effect was strongest within the first 5 years following cataract surgery. A similar protective association was noted for cataract surgery and Alzheimer’s dementia; conversely, glaucoma surgery was not associated with a reduced rate of dementia diagnosis. This analysis by Lee et al demonstrates that older adults undergoing cataract surgery may have a lower risk of developing dementia later in life. The findings of this study were strengthened by the large sample size and longitudinal follow-up, as well as the prospective nature of the work. Although this study was nonrandomized, several important potential confounding factors were controlled for. Some limitations of this study include the use of some self-reported data from participants, and the potential for residual confounding. Further study of this association amongst different populations should be pursued to validate these findings.

Click here to read this study in JAMA Internal Medicine

Relevant Reading: Association of co-occurring dementia and self-reported visual impairment with activity limitations in older adults.

In-Depth [prospective cohort study]:

The cohort for this study was derived from a database of the Adult Changes in Thought study, which contains a repository of data from older adults in the United States collected since 1994. Eligible patients underwent cognitive screening tests and physical evaluations at baseline, as well as biennially throughout the study period. Comorbidity data was assessed through patient self-reporting. Data regarding ophthalmologic disease and receipt of surgery was extracted through patients’ electronic medical records. Statistical analysis models were adjusted to account for measures of the following potential confounding variables: ​comorbidities (particularly cardiovascular disease), body mass index, self-rated health, activity limitations, physical activity, depression, retirement, and patient-reported vision problems. The hazard ratio (HR) for dementia amongst patients who had versus had not undergone cataract extraction surgery was 0.87 (95% confidence interval [CI] 0.62-0.83). The HR within 5 years of surgery was 0.68 (95% CI 0.56-0.81), and was 0.76 (95% CI 0.63-0.92) in later years. 14% of patients in this study received glaucoma surgery, which was not associated with a reduced risk of developing dementia. The hazard ratio was 1.08 (95% CI 0.75-.56) in comparing patients who had versus had not undergone glaucoma surgery over a follow up period of 5,029 person years. Several sensitivity analyses were performed, including the following: omitting patients enrolled between 1994-1996 (HR 0.52, 95% CI 0.39-0.96), excluding patients with surgery within 2 years (HR 0.57, 0.48-0.66) and considering incident cataract cases only (HR 0.70, 0.56-0.87). The reported results were robust to all sensitivity analyses.

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