Opposite Seasonal Variation in Nighttime and Morning Blood Pressure: A Longitudinal Study of Patients with Hypertension.

Authors

Tatsuya Maruhashi, Yoshihiko Kinoshita, Ryoji Ozono, Mitsuaki Nakamaru, Masanori Ninomiya, Jiro Oiwa, Takuji Kawagoe, Osamu Yoshida, Toshiyuki Matsumoto, Yasuo Fukunaga, Kotaro Sumii, Hironori Ueda, Nobuo Shiode, Kosuke Takahari, Yasuhiko Hayashi, Yujiro Ono, Yukiko Nakano, Masakazu Takahashi, Yasuki Kihara, Yukihito Higashi, Hiroshima NOCTURNE Research Group

Published in

American journal of hypertension. Jul 02, 2026. Epub Jul 02, 2026.

Abstract

Longitudinal data on seasonal variations in nighttime blood pressure (BP) obtained through home blood pressure monitoring (HBPM) are scarce. We examined whether nighttime BP is elevated in summer compared to winter in patients undergoing hypertension treatment.
Nighttime BP was measured for seven days using an HBPM device in 419 participants at baseline, and 136 of those underwent follow-up nighttime BP measurements at 6 months without any modification of antihypertensive therapy. Morning BP was also measured in some participants.
The baseline cross-sectional analysis indicated that nighttime systolic BP was elevated in summer compared to winter (adjusted mean difference, 8.3 mmHg; 95% confidence interval [CI], 4.7-11.8). The longitudinal analyses revealed that nighttime systolic BP was higher in summer than in winter among winter-to-summer participants (mean difference, 5.1 mmHg; 95% CI, 3.1-7.0; n = 36) and among summer-to-winter participants (mean difference, 2.6 mmHg; 95% CI, 0.3-5.0; n = 23). Conversely, morning systolic BP was lower in summer than in winter among winter-to-summer participants (mean difference, 3.8 mmHg; 95% CI, 0.7-7.0) and among summer-to-winter participants (mean difference, 3.7 mmHg; 95% CI, 1.0-6.4). In sensitivity analyses, seasonal variations in room temperature were positively correlated with changes in nighttime systolic BP (r = 0.43; 95% CI, 0.21-0.60) and negatively correlated with changes in morning systolic BP (r=-0.46; 95% CI, -0.63 to -0.25).
Nighttime systolic BP increased from winter to summer in association with higher room temperature and exhibited an inverse seasonal pattern compared to morning BP.

PMID:
42391606
Bibliographic data and abstract were imported from PubMed on 03 Jul 2026.

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