Room temperature affects BP measurements

Ambient temperature in the morning and in the evening both affect blood pressure (BP), a recent study has found. The interaction is stable and remains apparent throughout a yearlong observation.

A total of 401 adults (mean age 71±8 years, 259 women) participated in the study. Home BP was measured using a BP monitor. Morning measurements were collected between 3:00 and 9:59, while evening measurements were taken between 15:00 and 23:59. Room temperature was automatically detected by the same BP monitoring device; collections took place over a year.

Mean morning systolic (SBP) and diastolic (DBP) BP measurements were significantly higher than those taken at night (128±15 vs 122±14 mm Hg and 77±10 vs 72±8 mm Hg, respectively; p<0.0001 for both). Similarly, the mean room temperature was significantly higher during the morning (20.0±5.7 ^oC vs 22.4±4.9 ^oC; p<0.001).

Linear mixed models showed that the morning temperature was significantly and inversely associated with both SBP (coefficient, –0.5764, 95 percent confidence interval [CI], –0.6267 to –0.5264) and DBP (coefficient, –0.2515, 95 percent CI, –0.2275 to –0.2255; p<0.0001 for both). The same was true for evening temperature, yielding highly comparable estimates.

The linear model analyses were adjusted for confounders such as, age, body mass index, medication, mean outdoor temperature, and variation of temperature in each participant measurement.

Notably, the researchers also found that morning temperature remained significantly correlated with BP measurements across all months, except for July; evening temperature was associated with BP in all months.