BACKGROUND The riser pattern, an abnormal blood pressure (BP) rhythm in which sleep BP exceeds awake BP, is a predictor of future stroke events. Although the riser pattern is caused by autonomic dysfunction, its significance in heart failure (HF) patients is not established. HF patients often suffered from cognitive impairment (CI), but the relationship between riser pattern and CI is not clearly understood. We tested the hypothesis that the riser pattern is associated with mild CI, a form of brain damage that could develop to dementia. METHODS We performed Mini-Mental State Examination (MMSE), ambulatory BP monitoring (ABPM), echocardiography, and blood tests in 444 HF patients just before leaving hospitals. Mild CI, a measure of cognitive function, was defined as the score <26. RESULTS The mean age of the patients was 68±13 years; 61.5% were male; 22.5% were riser pattern. The MMSE score was significantly lower in the Riser group than in the Non-dipper and Dipper group (23±4 vs. 25±5, 26±4, respectively, P < 0.01). In multivariable logistic regression analysis, a riser pattern was significantly associated with mild CI (odds ratio 2.38, 95% confidence intervals 1.29-4.42, P < 0.01) after adjusting for significant covariates. CONCLUSIONS The riser pattern was associated with mild CI in HF patients. An abnormal circadian BP rhythm in HF patients is clinically significant as a potential indicator of subclinical brain damage.