Coexistence of PM_2.5 and low temperature is associated with morning hypertension in hypertensives

We tested the hypothesis that concentration of PM_2.5 is associated with home BP level. We analyzed home BP data for 91 consecutive days in 40 hypertensives. PM_2.5 solely was not correlated with home BP levels, but low temperature was associated with a 1.6-fold increased likelihood of morning hypertension (p < 0.001) under the condition of high PM_2.5 concentration. In addition, coexistence of low temperature and high PM_2.5 was associated with a 2.3-fold increased likelihood of morning hypertension (p < 0.001) compared with high temperature and low PM_2.5 condition. Environmental and meteorological factors could be important causes of enhanced home BP elevation.