"Morning BP Action in Winter" initiative: confronting cardiovascular "heat shock"

Seasonal variations in blood pressure (BP) and cardiovascular risk represent one of the most consistently reproduced yet under-recognized phenomena in hypertension research. In Japan, where winter temperatures can fluctuate sharply in both outdoor and indoor environments, the burden of winter-associated cardiovascular events is strikingly visible in epidemiological data. The so-called "heat shock" phenomenon is defined as acute cardiovascular events triggered by sudden temperature changes. Recent statements by the Japanese Society of Hypertension, including the initiative "Morning BP Action in Winter," emphasize that winter mornings constitute a uniquely hazardous physiological "heat shock" window-one in which sympathetic activation, thermal stress, and behavioral triggers converge to sharply elevate BP and precipitate acute cardiovascular events. This editorial commentary expands on the scientific rationale, clinical implications, and public health significance of this initiative, aiming to contextualize winter morning BP management as an essential preventive strategy.