Seasonal influences on blood pressure in high normal to mild hypertensive range.

Abstract

To investigate the seasonal influences on various arterial blood pressure measurements, 22 subjects in the high normal to mild hypertensive range were examined twice following the same protocol. In one group (13 subjects), measurements were first done in warm conditions and repeated 5-7 months later in cold conditions; in the second group (nine subjects) a reverse sequence was followed. Blood pressure was measured under casual conditions during a hand grip exercise test, mental arithmetic test, and submaximal multistage bicycle exercise test; during the following 24 hours, blood pressure was measured serially with a noninvasive ambulatory blood pressure recorder. Daily outdoor maximum and indoor laboratory temperatures were also obtained. In the cold season, significantly higher values (on the average by 5 -10 mm Hg, /7<0.01) were obtained in both groups for mean diastolic daytime blood pressure. For other measurements, a trend toward higher values in the cold season was observed in both groups, although statistical significance was not obtained in all instances. For nighttime measurements, irrespective of the seasonal sequence, lower values were observed in the second session. Significant correlations were found between the differences in the average daytime ambulatory blood pressures and the corresponding changes of daily maximum outdoor temperatures after 5-7 months. These observations indicate that arterial blood pressure may be strongly influenced by environmental temperature. This phenomenon should be taken into account both in the evaluation of the individual hypertensive patients and in the design and analysis of studies on arterial hypertension, especially when ambulatory blood pressure techniques are employed. {Hypertension 1989; 14:22-27) T hat hypertensive patients often need less pharmacological treatment in summer than in winter is a common experience in clinical practice. In fact, a definite seasonal influence on arterial blood pressure (with values during the winter higher by 2-10 mm Hg than in the summer) has been demonstrated by various studies based on single or repeated measurements that were obtained by a standard sphygmomanometer and by a recent study in children whose blood pressure measurements were taken with an automatic recorder.

Do geomagnetic disturbances of solar origin affect arterial blood pressure?

“…Almost all relations were still significant when other potential confounding factors were taken into account, including season, which is related to geomagnetic activity (because of the varying distance of the earth from the sun in the different seasons) 8 and has been reported to influence BP. 12 Inspection of Figure 1 and calculations from the estimated regression slopes are consistent in indicating that, for extreme values of geomagnetic disturbances a difference of about 6 to 8 mm Hg in systolic and diastolic BPs may be expected. It may be interesting to note that these effects are of the same order of magnitude as those reported for the influence of other individual, lifestyle and environmental factors on BP such as sodium consumption, 13 body weight, 14 alcohol consumption 15 and external temperature.…”

Self-monitoring of home blood pressure with estimation of daily salt intake using a new electrical device

“…Thus, we expected to be able to manage daily relative salt intake, although there was a possibility that the predicted salt value would differ from the real value, if a relatively long period was required for representative results and we used the moving 3-day moving average. Daily blood pressure changes not only because of salt intake but also because of temperature change, 31 day of the week 32 and change of sympathetic nervous system activity. As morning blood pressure in particular fluctuates, it takes a long interval to examine accurately the relationship between salt excretion and morning blood pressure.…”

Subarachnoid Hemorrhage Incidence in the United States Does Not Vary with Season or Temperature

“…Circadian and seasonal variations in blood pressure, infection frequency, ethanol and tobacco use, and sedentary behavior, in addition to alteration in blood pressure after strenuous exertion in colder climates, have all been proposed as mechanisms to explain seasonal variation in SAH. [26][27][28][29][30][31][32][33][34][35][36][37][38][39] Despite these well-established effects, the seasonal effects reported by some groups have not always been consistent with respect to timing, and other studies have failed to demonstrate any seasonal relationship. 23,24,[37][38][39][40][41][42] Thus, there remains no consensus regarding the influence of season and/or weather on the incidence rate of SAH.…”