Alteration in cardiac autonomic activity during sleep is a common feature of sleep disorders. Diurnal sympathetic overactivity is a possible consequence and could contribute to future cardiovascular complications. The aim of this study is to assess the relationship between cardiac autonomic activity during sleep and diurnal autonomic cardiovascular control. In a large cohort (n = 1011) of subjects aged 65 years old (±0.4) free of cardiac and cerebrovascular events and of sleep-related breathing disorders, we evaluated (cross-sectional study) the prevalence of unexpected alteration in sleep-related autonomic overactivity according to the presence of a cyclical nocturnal heart rate variability [quantified using the relative power spectral density of the very low-frequency band of the heart rate increment (VLFi %) from ECG Holter monitoring]. We tested its relationship with diurnal ambulatory blood pressure and spontaneous baroreflex sensitivity (sBRS). An abnormal cardiac autonomic activity during sleep was retained in 34.4 % of this population according to a VLFi % >4. Using multiple logistic regression analysis, the severity of the autonomic alteration was mainly correlated after adjustment with lower sBRS (p = 0.01; OR: 0.94; 95 % CI: 0.90–0.98). Diurnal baroreflex control alteration is associated with sleep-related autonomic overactivity elderly. Such alteration may contribute to the increased incidence of cardiovascular complications in sleep disorders.