Is hemodialysis itself a risk factor for dementia? An analysis of nationwide registry data of patients on maintenance hemodialysis in Japan

Background: Chronic kidney disease is a major risk factor for dementia, but the influence of hemodialysis itself on the development of dementia remains unclear. We previously reported that non-diabetic patients on maintenance hemodialysis have preserved cognitive function; hemodialysis removes blood amyloid β (Aβ), which is a major cause of Alzheimer's disease in the brain; and the number of Aβ deposits in the postmortem brains of hemodialysis patients was significantly less compared to that in age-matched controls not undergoing hemodialysis. We aimed to evaluate the influence of hemodialysis on the development of dementia. Methods: We accessed the Japanese Society for Dialysis Therapy Renal Data Registry between December 31, 2009, and December 31, 2010. Dementia was identified in 120,101 patients undergoing maintenance hemodialysis. The association between hemodialysis duration and dementia risk was analyzed using logistic regression analysis. Results: There was a significant decrease in the dementia risk with an increase in the hemodialysis duration, with odds ratios (95% confidence intervals) of 0.78 (0.74-0.82) and 0.88 (0.78-0.99) for every 10 years in non-diabetic and diabetic patients, respectively. However, in diabetic patients, the correlation between hemodialysis duration and dementia risk was not consistent. Conclusion: A longer hemodialysis duration was correlated with a lower dementia risk, but the correlation between hemodialysis duration and dementia risk in diabetic patients was much weaker and vaguer than that in non-diabetic patients. This finding does not appear to contradict greatly the assumption that the reduction in dementia risk with a prolonged hemodialysis duration in non-diabetic patients was caused not only by the survivor effect but also by hemodialysis itself.