A large study of more than 40,000 people over almost a decade convincingly proved that climate changes have a direct impact on blood pressure. In general, blood pressure is better in the summer and worse in the winter, regardless of the climate in which you live.
For example, people who live in Minnesota or Wisconsin experience large temperature changes between the seasons. Summer days routinely top 80 degrees, while winter days often drop below zero. However, the seasonal fluctuations in their blood pressure are the same as someone who lives in Phoenix, where the climate is – overall – much warmer all year long. Even though it’s warmer in Phoenix overall, there is still temperature fluctuation between summer and winter. The key seems to be change in average temperature, not how big that change is.
Several smaller studies have added more interesting ideas to this topic. Seasonal fluctuations in blood pressure change quickly if one moves from a warmer climate to a colder climate, and more slowly when moving from a colder climate to a warmer climate. So, moving from Phoenix to Siberia will cause a quick change in your blood pressure that first winter, but moving from Siberia to Phoenix won't.
Nobody is really sure why this happens. One of the underlying factors is surely tied to changes in average blood vessel diameter. Blood vessels shrink when they cool down, so people who spend more time in cold climates have more exposure to weather that causes the vessels in the skin to contract. Averaged over time, this leads to slightly increased blood pressure. This change, though, is not enough to explain the entire phenomenon.
Some scientists have suggested that colder climates tend to be darker and that associated changes in Vitamin D production (directly tied to amount of sun exposure) play a role. Others have suggested that even more subtle systems – like hormone changes caused by shifts in the angle of the sunlight that does reach the skin – might have important effects.
Because high blood pressure treatment should be tailored to your specific blood pressure, these seasonal effects should already be adjusted for in your treatment, and it’s unlikely that you’ll need different doses of medicine – or different medicines – for the summer and winter seasons.
1. Hayashi T, Ohshige K, Sawai A, Yamasue K, Tochikubo O. Seasonal influence on blood pressure in elderly normotensive subjects.Hypertens Res. 2008 Mar;31(3):569-74.
2.Morabito M, Crisci A, Orlandini S, Maracchi G, Gensini GF, Modesti PA. A synoptic approach to weather conditions discloses a relationship with ambulatory blood pressure in hypertensives. Am J Hypertens. 2008 Jul;21(7):748-52.