Parallel Morning and Evening Surge in Stroke Onset, Blood Pressure, and Physical Activity
To the Editor:
I read with great interest the excellent study by Stergiou et al.1 It demonstrates what has been predicted by an afternoon increase in blood pressure and heart rate in patients when awakening from a siesta.2 Actually, it was shown that the siesta might be a novel risk factor for vascular mortality in elderly subjects.3 Moreover, it was found that this occurs after an afternoon sleep but not when those who practice it just rest in bed without sleeping.4
Thus, it corroborates the prediction by Mulcahy et al5 that the siesta may in fact be a “snooze induced excitation of triggered sympathetic activity”5 rather than a protective activity as usually intuitively perceived.6,7⇓
On the background of the exciting findings of Stergiou et al,1 it is interesting to speculate that the overlooked and thus as-yet-unidentified habit of the siesta in the agricultural and hot “stroke belt” in the United States may account for the as-yet-unexplained excess of strokes in that area.8
- ↵Stergiou GS, Vemmos KN, Pliarchopoulou KM, Synetos AG, Roussias LG, Mountokalakis TD. Parallel morning and evening surge in stroke onset, blood pressure, and physical activity. Stroke. 2002; 33: 1480–1486.
- ↵Kalandidi A, Tzonou A, Toupadaki N, Lan SJ, Koutis C, Drogari P, Notara V, Hsieh CC, Toutouzas P, Trichopoulos D. A case-control study of coronary heart disease in Athens, Greece. Int J Epidemiol. 1992; 21: 1074–1080.
- ↵Perry HM, Roccella EJ. Conference report on stroke mortality in the southeastern United States. Hypertension. 1998; 31: 1206–1215.
We thank Dr Bursztyn for his interest in our article. The hypothesis he advances is quite interesting, but the existing evidence is too limited to allow judgment as to whether the siesta habit affects in a beneficial1 or a detrimental way2 the occurrence of cardiovascular events.
It is clear that our study was designed not to address this issue but to investigate the timing of stroke onset within the 24-hour period compared with the diurnal variation in blood pressure and physical activity.3 Nevertheless, one might attempt to compare the afternoon trough with the evening peak in stroke incidence in our study. Thus, a hypothetical diurnal variation curve (the Figure, dotted line) for stroke onset in subjects who do not take a siesta might be added in the figure of the diurnal variation curve observed in our study.3 Comparison of the observed with the hypothetical 24-hour curves suggests that the practice of siesta may be associated with stroke protection (afternoon trough “a,” where the incidence of stroke was reduced during siesta) or with increased risk for stroke (evening peak “b,” where a surge in the incidence of strokes was observed). Whether the excess risk for stroke on waking and rising in the evening overcomes the afternoon protection during siesta depends on the curve-fitting parameters.
Perhaps a direct comparison of stroke incidence in patients who regularly take a siesta with those who regularly do not would allow a critical evaluation of the 2 alternative hypotheses.1,2⇓ Unfortunately, although the practice of siesta is known to be common in the population included in our study, specific information on this issue for stroke patients was not obtained. Therefore, at present the evidence regarding the effect of siesta on cardiovascular risk is weak.