The effect of a change in ambient temperature on blood pressure in normotensives

The aim of this study was to investigate the influence of ambient temperature on blood pressure (BP). BP measurements were taken in 20 normotensive volunteers who stayed in Greenland for a 6-week period. Measurements of systolic (SBP), diastolic (DBP) and heart rate (HR) were taken before (3 sessions), during (7-8 sessions) and after the journey (3 sessions). Each session consisted of five BP measurements in the supine position after at least 5 min rest. All five readings were averaged. Temperature data (mean +/- s.d.), collected from meteorological services, before, during and after Greenland were 15.7 +/- 0.6, 0.5 +/- 1.5 and 8.2 +/- 0.8 degrees C. SBP values were 116 +/- 7.0, 122 +/- 7.6 and 116 +/- 7.4 and DBP 63 +/- 5.2, 66 +/- 5.8 and 65 +/- 6.5 mm Hg, respectively. HR amounted to 58 +/- 7.4, 61 +/- 6.7 and 60 +/- 7.4 bpm. Significant differences existed between, before and during for SBP and DBP and between, during and after for SBP. Readings were grouped in four categories based on the temperature at the time of reading. For SBP as well as DBP a clear dose-response relationship was demonstrated between low temperature and high BP, although for DBP only a few correlations were statistically significant. Mean correlation coefficients for SBP and DBP against temperature were -0.44 (P < 0.001) and -0.27 (P < 0.005), respectively. our results are in favour of a moderate, but both significant and relevant increase in sbp and dbp when moving from higher to lower ambient temperature.