Moderate renal impairment and risk of dementia among older adults: the Cardiovascular Health Cognition Study.

Renal impairment is associated with an increased risk of carotid atherosclerosis and stroke, determinants of cognitive dysfunction and dementia. The purpose of this study was to determine whether moderate renal impairment is associated with incident dementia among community-dwelling older adults. Participants in the Cardiovascular Health Cognition Study without prevalent dementia (n = 3349) were included in the analysis. Incident dementia was confirmed through neurologic testing. Renal function at baseline was estimated by the inverse of serum creatinine (1/SCr); moderate renal impairment was defined as SCr > or = 1.3 mg/dl for women and > or = 1.5 mg/dl for men. Cox regression models were used to estimate the association of renal impairment with incident dementia. Because SCr is also a function of muscle mass, the authors determined whether the relationship between SCr and dementia was particularly strong among individuals without severe co-morbidity at baseline, as reflected by self-reported general health status. There were 477 incident dementia cases over a median 6 yr follow-up. After adjustment for potential confounders, moderate renal insufficiency was associated with a 37% increased risk of dementia (95% CI = 1.06 to 1.78). Similarly, a 0.5-unit decrement in 1/SCr (equivalent to an increase in SCr from 1.0 to 2.0 mg/dl) was associated with a 26% increased risk (95% CI = 1.02 to 1.60). These associations were present only among the 84% of older adults who reported good-excellent health. Among those in good-excellent health, higher SCr was associated with vascular-type dementia but not Alzheimer-type dementia. Moderate renal impairment, reflected by a higher SCr, is associated with an excess risk of incident dementia among individuals in good-excellent health. Strategies to prevent or delay the onset of dementia in patients with moderate renal impairment are needed.