30 September 2019:
Cardiovascular changes during nocturnal hot flushes
Summary
Baker et al (1) have recently investigated cardiovascular changes that occur with nocturnal hot flushes during sleep. They investigated changes in heart rate, blood pressure, and pre-ejection period in 86 women aged between 43-60 years who had at least one objectively-recorded nocturnal hot flush during an overnight laboratory PSG recording. Fifty-one percent of the nocturnal hot flushes were associated with arousals/awakenings and these were accompanied by an increase in systolic (~6 mmHg) and diastolic (~5mmHg) blood pressure and heart rate (~20% increase), sustained for several minutes. In contrast, nocturnal hot flushes not resulting in arousal/awakening, which occurred in 28.6% cases, were accompanied by a drop in systolic blood pressure and a marginal increase in heart rate, likely components of the heat dissipation response. All nocturnal hot flushes were accompanied by decreased pre-ejection period, suggesting an increased cardiac sympathetic activity, with a prolonged increase for nocturnal hot flushes associated with arousals/awakenings. Older age predicted greater likelihood of nocturnal hot flush arousals/awakening.
Commentary
The findings of this study suggest that nocturnal hot flushes associated with arousals/awakenings, which are in the majority and more likely in older women, lead to increases in heart rate and blood pressure, which could have a long-term impact on nocturnal cardiovascular restoration in women with multiple nocturnal hot flushes. Sleep is not a passive event, but rather an active process involving characteristic physiological changes that occur throughout the body(2). There are a variety of physiological and behavioral changes during normal wakefulness, NREM and REM sleep which are most commonly noted in the somatic and autonomic nervous system and affect the respiratory, cardiovascular, gastrointestinal, endocrine, renal, sexual and thermoregulatory systems. Heart rate, blood pressure, cardiac output, and peripheral vascular resistance decrease during NREM sleep and decrease further in REM sleep.