The association between cataract and incidence of cognitive impairment in older adults: A systematic review and meta-analysis

Background: Cataract has been shown to be associated with an increased risk of cognitive impairment. However, the results of previous studies have been inconsistent. This systematic review and meta-analysis aimed to investigate the association between cataract and the incidence of cognitive impairment in older adults.Methods: A comprehensive search of electronic databases from inception to January 2023 was performed to identify relevant studies. Data were extracted from eligible studies and a meta-analysis was performed to calculate the pooled hazard ratio (HR) and 95% confidence interval (CI).Results: We included 13 studies with 25 study arms involving a total of 798,694 participants. Compared with participants without cataract, those with cataract had a higher risk of developing all-cause dementia (pooled HR: 1.22; 95 % CI: 1.08-1.38; I2 =86 %; 9 studies), Alzheimer's disease dementia (pooled HR: 1.18; 95 % CI: 1.07-1.30; I2 =0 %; 9 studies), vascular dementia (pooled HR: 1.21; 95 % CI: 1.02-1.43; I2 =77 %;3 studies) and mild cognitive impairment (pooled HR: 1.30; 95% CI: 1.13-1.50; I2 =0%;2 studies). There was no significant association between cataract and mixed dementia (pooled HR: 1.03; 95 % CI: 0.52-2.04; I2 =78 %;2 studies). We assessed the risk of bias of the included studies using the Newcastle-Ottawa Scale and found that most of them had a low or moderate risk of bias. The number of studies in each meta-analysis ranged from two to nine, with more studies available for all-cause dementia and Alzheimer's disease dementia than for vascular dementia and mixed dementia.Conclusions: The findings suggest that cataract may be associated with cognitive impairment in older adults. However, the causal relationship between cataract and cognition remains unclear and requires further investigation.