OBJECTIVE: Although decreased heart rate variability (HRV) has been well-documented in association with depression after myocardial infarction, this phenomenon has not been studied in patients with stroke. The present study was designed to prospectively assess heart rate in relationship to depression among patients with acute stroke. DESIGN: Using 24-hour Holter monitoring, HRV was assessed. SETTING: A large university rehabilitation hospital. PARTICIPANTS: Patients with first ever stroke and no other severe physical illness, cigarette smoking, or drug therapy that could affect HRV were evaluated over 24 hours for HRV. MEASUREMENTS: Patients were evaluated using the Structured Clinical Interview for depression diagnosis. Severity was assessed by the Hamilton Depression Rating Scale. Stroke severity was assessed by the National Institutes of Health Stroke Scale, the Barthel Index, and the Mini- Mental State Exam. The standard deviation (SD) of time in milliseconds of normal to normal beats (SDNN) was the primary measure of HRV. RESULTS: Among patients with poststroke major or minor depression (N = 33), the SDNN was 109 +/- 32.6 SD compared with nondepressed patients (N = 16) whose SDNN was 133.9 +/- 40.1 SD (Wilcoxon rank test S = 492, p = 0.048). The SDNN was significantly and independently related to the existence of depression, but no other intergroup differences. CONCLUSIONS: These findings, for the first time, have provided some evidence that both major and minor poststroke depression may lead to decreased HRV. Future research in larger groups of patients should determine whether other measures of HRV more specific to sympathetic-parasympathetic tone are decreased in patients with poststroke depression.