Chronic kidney disease is associated with incident cognitive impairment in the elderly: the INVADE study

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Abstract
Background. Limited data exist regarding the relationship between decreased renal function and cognitive impairment. Methods. A total of 3679 participants of the Intervention Project on Cerebrovascular Diseases and Dementia in the Community of Ebersberg (INVADE) composed the community-based cohort study. Measures of renal function were estimated using the Cockcroft–Gault equation and divided into normal, mild and moderate-to-severe impaired renal function (creatinine clearance ≥60, 45–59 and 2, respectively). The main outcome measures were cognitive impairment at baseline and new cognitive impairment after a 2-year follow-up. Cognitive function was measured using the 6-Item Cognitive Impairment Test (6CIT). Multiple logistic regression analysis was used to assess the association between renal function and cognitive impairment. Results. At baseline, 396 participants (10.8%) had cognitive impairment. After the 2-year follow-up, 194 participants (6.2%) developed new cognitive impairment. The incidence of cognitive impairment across the groups with normal renal function, mild and moderate-to-severe kidney disease at baseline were 5.8, 9.9 and 21.5%, respectively. Multiple logistic regression analysis after adjustment for possible confounders including traditional cardiovascular risk factors showed a significant association for participants with moderate-to-severe kidney disease at baseline to develop new cognitive impairment after the 2-year follow-up [odds ratio: 2.14 (95% confidence interval: 1.18–3.87), P = 0.01]. Conclusions. In summary, moderate-to-severe impaired renal function is associated with incident cognitive impairment after 2 years in a large cohort of elderly subjects.