Sympathetic-Nerve Activity during Sleep

To the Editor: Somers et al. (Feb. 4 issue)¹ found that rapid-eye-movement (REM) sleep is associated with profound sympathetic activation in normal subjects. Because sleep cycles change with aging, the hemodynamic and sympathetic changes found during REM sleep in these subjects, whose mean age was 25 years, cannot be extrapolated to explain ischemic events that occur in much older patients. If such sleep-related changes were also found in older people, this might help clarify the higher-than-expected incidence of myocardial infarction and stroke in the morning hours. There is, however, a more likely explanation for this phenomenon. The ischemia may have…