title: 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)-mean 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, P = 0.002; morning diastolic BP, 84.4 ± 0.9 vs. 82.6 ± 0.9 mm Hg, P = 0.02; and prewaking morning BP surge, 20.8 ± 1.3 vs. 15.3 ± 1.3 mm Hg, P = 0.0004). 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%, P = 0.01). 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.
authors.affiliation: Third Division, Department of Internal Medicine, Osaka Medical College, Osaka, Japan. shougo17@gb3.so-net.ne.jp
authors.forename: Shougo
authors.initials: S
authors.lastname: Murakami
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Otsuka
authors.forename: Tatsuji
authors.initials: T
authors.lastname: Kono
authors.forename: Akiko
authors.initials: A
authors.lastname: Soyama
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Umeda
authors.forename: Naomune
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Hideaki
authors.initials: H
authors.lastname: Morita
authors.forename: Gaku
authors.initials: G
authors.lastname: Yamanaka
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kitaura
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D013696:Temperature