Impact of outdoor temperature on prewaking morning surge and nocturnal decline in blood pressure in a Japanese population

Abstract

Seasonal variations in blood pressure (BP) have often been attributed to meteorological factors, especially changes in outdoor temperature. We evaluated the direct association between meteorological factors and circadian BP variability. Twenty-four-hour ambulatory BP was monitored continuously for 7 days in 158 subjects. Mean awake, asleep, morning (first 2 h after waking) BP, prewaking morning BP surge (morning systolic BP (SBP)Àmean SBP during the 2-h period before waking) and nocturnal BP decline were measured each day. We compared BP values for the lowest and highest days with regard to the daily mean outdoor temperature and mean atmospheric pressure. Morning BP and prewaking morning BP surge on the coldest day were significantly higher than those on the warmest day (morning SBP, 136.6±1.6 vs. 133.1±1.5 mm Hg, P¼0.002; morning diastolic BP, 84.4±0.9 vs. 82.6±0.9 mm Hg, P¼0.02; and prewaking morning BP surge, 20.8±1.3 vs. 15.3±1.3 mm Hg, P¼0.0004). The magnitude of nocturnal BP decline on the coldest day was significantly greater than that on the warmest day (15.8 ± 0.7 vs. 13.9 ± 0.7%, P¼0.01). Outdoor temperature is an important determinant of morning BP, prewaking morning BP surge and the magnitude of nocturnal BP decline. These findings may have important implications in management of hypertension and prevention of cardiovascular events. Keywords: ambulatory blood pressure monitoring; cold pressure stress; outdoor temperature; prewaking morning blood pressure surge INTRODUCTION Previous studies have indicated that the onset of cardiovascular events show circadian, weekly and seasonal variations. [1][2][3] Many studies have demonstrated an increased incidence of acute cardiovascular events in winter compared with other seasons. Blood pressure (BP) has also been reported to be higher in winter than in the other three seasons. [4][5][6][7][8] This seasonal variation in BP has often been attributed to meteorological factors, especially changes in outdoor temperature. However, direct effects of outdoor temperature and atmospheric pressure on BP have yet to be established conclusively, as seasonal changes in other factors such as diet, 9 physical activity 10 and psychological status 11 that may affect BP have also been observed.In this study, we evaluated the effect of outdoor temperature and atmospheric pressure on BP variability in a Japanese population using continuous 24-h ambulatory BP (ABP) monitoring for a 7-day period.

Diurnal Blood Pressure Rhythmicity in Relation to Environmental and Genetic Cues in Untreated Referred Patients

“…BP phenotypes are probably more closely related to the mediumto-long-term variation in atmospheric conditions rather than to the short-term variation, as exemplified by our current 24-hour ambulatory monitoring enabled us to study the BP rhythmicity during the whole day. [9][10][11][16][17][18][19][20] Our methods were concordant with a recent study 11 that also applied multivariable regression analyses to investigate the independent effects of host and environmental factors, including personal-level temperature, relative humidity, atmospheric pressure, and daylight hours (seasonality). However, the outcome variables in this study were 24-hour daytime and nighttime BPs instead of the night-to-day BP ratio.…”

“…The time a person habitually spends awake and asleep, 5 physical and psychological stressors on weekdays versus weekends, 6 smoking, 7 and drinking 8 all impact on the diurnal BP rhythmicity. Environmental cues include seasonality, 9 ambient temperature, 10 atmospheric pressure, and humidity. 11 Numerous studies dating back to the early 1980s described the influence of atmospheric conditions, 9-15 most often temperature, 10,13,14 on the conventionally measured office BP or on the out-of-the-office BP 13 either measured by home 14 or ambulatory monitoring.…”

“…Environmental cues include seasonality, 9 ambient temperature, 10 atmospheric pressure, and humidity. 11 Numerous studies dating back to the early 1980s described the influence of atmospheric conditions, 9-15 most often temperature, 10,13,14 on the conventionally measured office BP or on the out-of-the-office BP 13 either measured by home 14 or ambulatory monitoring. 10 However, all but 8 studies [9][10][11][16][17][18][19][20] provided information on the BP level and not on the BP rhythmicity during the day.…”

Association between visit-to-visit clinic blood pressure variability and home blood pressure variability in patients with chronic kidney disease

“…8,[24][25][26][27][28][29] In addition, various physiological or behavioral factors, including waking and sleep cycles, mental and physical stress, temperature, and alcohol intake can affect both HBPV and VVV. [30][31][32][33][34] Previous studies have shown the factors affecting HBPV, including older age, female gender, high HBP and alcohol intake. 25,[30][31][32] The factors affecting VVV were almost similar to those affecting HBPV in several studies, including older age, female gender, high mean systolic clinic BP and history of myocardial infarction.…”

The risk of cold temperature: an important aspect of the determination of morning blood pressure surge

“…This cold temperature-augmented morning BP increase may partly account for the increased number of CVDs on cold mornings during the winter season. 17 In the current issue of Hypertension Research, Murakami et al 18 make an important contribution toward our understanding of the association between cold temperature and morning BP increase. In this cross-sectional survey of 158 subjects who had performed 24-h ambulatory BP monitoring continuously for 7 days (mean 58 years; men: 41%), the authors evaluated the association between meteorological factors (outdoor temperature and atmospheric pressure) and circadian BP variability.…”