Effects of aging and cardiac denervation on heart rate variability during sleep

Background-Cardiac vagal predominance increases the RR interval and RR high -frequency (HF) variability during non-rapid eye movement (non REM) sleep ( stages I through IV) in young subjects. Aging suppresses deep sleep, but ef fects of age-related changes in sleep architecture on RR are unknown. Wheth er mechanical effects of changes in the breathing pattern on the sinus node during sleep affect RR variability is unclear. Methods and Results-Polygraphic sleep recordings and RR and RR spectral pro files were determined in 8 young (22.5+/-3.3 years) and 8 older (55.0+/-7.3 years) healthy volunteers. HF oscillations in RR of 8 cardiac-denervated h eart transplant recipients determined mechanical effects of respiration on the sinoatrial node during sleep. Transition from wakefulness to non-REM sl eep increased the RR interval in young and older subjects and increased the HF variability of RR in the young (P<0.05) but not in the older subjects. Older subjects disclosed a faster RR (P<0.01) and a lower HF variability (P <0.05) during non-REM sleep than the young subjects. Aging did not affect l ight and REM sleep but decreased deep sleep (stage IV) from 39+/-23 to 6+/- 6 minutes (P<0.001). Reduction in sleep stage IV with aging blunted the inc rease in RR and in RR HF variability during non-REM sleep (r>0.55, P<0.05). Transition from wakefulness to non-REM sleep doubled the markedly reduced HF variability of RR in the heart transplant recipients (P<0.05). Conclusions-Disappearance of deep sleep with aging impairs nocturnal increa se in cardiac vagal activity. Mechanical effects of changes in breathing pa ttern during sleep favor increases in HF oscillations of the RR interval du ring non-REM sleep.