Abstract 12819: An Inadequately Heated Environment Increases Morning Blood Pressure and Morning Blood Pressure Surge in Winter: A Randomized Controlled Trial
Introduction: Excess mortality rate due to heart disease and stroke in winter has been associated with higher blood pressure (BP) and increased intraday variability during this season. However, evidence from randomized controlled trial is lacking.
Hypothesis: We assessed the hypothesis that 10°C lower room temperature increases morning BP and its surge among healthy participants.
Methods: A total of 146 participants aged 18–65 years was randomly assigned to an inadequately heated environment (target temperature 12°C) or a control environment (22°C). All participants were asked to remain in the experimental room from 9:00 pm to 6:00 am, stay awake until 11:00 pm, and rise by 6:00 am. BP was measured by ambulatory BP monitoring at 30 minute intervals. Sufficient amount of clothing and blankets were made available for the participants. Outcome measures included (1) morning BP: average in 2 hours after wake-up time; (2) lowest sleeping BP: average of three BP readings centered on the lowest sleeping readings and (3) morning BP surge: (1) minus (2).
Results and Conclusion: In a baseline survey conducted to determine the self-controlled temperature in all participants, the outcome measures did not differ by >1.0 mmHg in the two groups.As the result of intervention to 140 participants (5:did not attend intervention, 1:morning BP was not available), systolic BP (SBP) were significantly higher in the inadequate heating group (mean temperature ± SEM: 14.3 ± 0.3°C) than in the control group (24.2 ± 0.2°C) for morning BP (mean ± SEM: 121.1 ± 1.7 vs.114.0 ± 1.5 mmHg; P<0.01) and morning BP surge (21.9 ± 1.3 vs. 14.3 ± 1.1 mmHg; p<0.01). We found no significant difference in the lowest sleeping BP (99.2 ± 1.4 vs. 99.7 ± 1.4 mmHg; P=0.78). The average amount of clothing and blankets used in the inadequate heating group were greater than that used in the control group by 1747 g and 2230 g, respectively. In conclusion, a 10°C lower ambient temperature increased the morning BP and morning BP surge.
- © 2010 by American Heart Association, Inc.