Hypertension: What happens to blood pressure in cold weather?

Blood pressure measures the amount of pressure placed against the walls of the arteries as blood flows through them.

A person’s blood pressure measurement is comprised of two different numbers:

• the top number is the systolic blood pressure, measuring the maximum pressure in the arteries when a person’s heart beats or contracts
• the bottom number is the diastolic blood pressure, measuring the lowest pressure in the arteries while the heart is relaxed.

Blood pressure is measured in millimeters of mercury (mm Hg).

Normal blood pressure includes a systolic measurement of less than 120 mm Hg, and a diastolic reading of less than 80 mm Hg.

Blood pressure is considered high with a systolic measurement of 130 mm Hg or more, and a diastolic reading of 80 mm Hg or more.

High blood pressure can sometimes occur without any symptoms, which is why it is important to have your blood pressure regularly checked.

Although the main cause of hypertension is still unknown, past research does show certain factors can increase a person’s risk for developing high blood pressure such as obesity, ethnicity, insulin resistance, smoking, and a high-salt diet.

People with high blood pressure are also at an increased risk for developing other diseases, including:

Previous studies have shown there is a seasonal variation when it comes to blood pressure.

Generally speaking, blood pressure tends to increase during the cold weather months and decrease during the warmer weather months.

“One of the main ways in which blood pressure gets regulated in the body is the arteries either clamping down or loosening up — we call that vasoconstriction and vasodilation,” explained Dr. Yu-Ming Ni, a board-certified cardiologist and lipidologist at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in Fountain Valley, CA, who was not involved in the recent study study.

“If it’s cold outside, you become vasoconstrictive, so the arteries tighten up and the blood pressure goes higher. If you feel hot, then the blood vessels dilate and you get vasodilation that can cool the body down,” Dr. Ni explained for Medical News Today.

A study in April 2021 found that just increasing a room’s temperature by 10 degrees can cause a significant change in systolic blood pressure.

Another study in February 2016 found older adults living in cold homes of less than 64 degrees Fahrenheit had higher blood pressure, poorer biomarker values in the blood, and worse lung conditions.

For this study, researchers reviewed electronic health records for over 60,000 adults treated for high blood pressure between July 2018 and June 2023 at six healthcare centers.

Study participants were an average of 62 years old. More than half identified as Caucasian and about 60% identified as female.

When analyzing seasonal blood pressure readings, scientists found that, on average, a study participant’s systolic blood pressure rose by up to 1.7 mm Hg in the winter months compared to the summer months.

Additionally, researchers found that participant blood pressure control rates decreased by up to 5% during the cold weather months.

“The findings supported the existence of seasonal variation in blood pressure, which has been noted in previous studies,” Robert B. Barrett, a software engineer at the American Medical Association in Greenville, SC, and lead author of this study explained to MNT.

“Despite the smaller degree of systolic blood pressure variation, we were surprised to observe a great degree of change in blood pressure control between winter and summer months. Additionally, [the] temperate season was indicated as a significant predictor of visit control — a feature which has not been extensively described before.”

– Robert B. Barrett

Because people with high blood pressure are less likely to have their blood pressure controlled in winter compared to summer, Barrett said more physician and lifestyle interventions may be necessary.

“Seasonal variation in blood pressure has a substantial effect on hypertension control, often defined as blood pressure 140/90,” he continued. “If the blood pressure is very well controlled, for example to 130/80, then seasonal variation will have little effect on control to 140/90.”

“However, if blood pressure is not well controlled, then patients near the 140/90 level could benefit from monitoring their blood pressure regularly, closer medical follow-up, and avoiding decreased physical activity and increased weight toward year-end,” Barrett added. “Some patients may benefit from increased pharmacological intervention to keep blood pressure controlled during the winter.”

After reviewing this study, Dr. Cheng-Han Chen, interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, not involved in the research, told MNT that, while these findings add previous studies looking at seasonal variation and high blood pressure, this study is significant due to the large and varied participant pool.

“This study is important for informing physicians on how tightly we have to monitor a patient’s blood pressure, depending on the season,” he continued. “For instance, this tells us that we should pay extra attention to having accurate measurements during the winter months, as we may need to adjust the medications during this time to get the blood pressure under control.”

“The next step [in this research] would probably be some sort of either public outreach or physician education on this type of effect,” Dr. Chen added.

“I think most of us are not really too aware of this cold weather effect on blood pressure. A lot more physician education on the importance of blood pressure controls, specifically during the colder winter months, [would] help patients,” he admitted.

Dr. Ni agreed that the findings were not surprising, but said it is good to have a study on this topic as there still remain questions on how weather affects blood pressure.

“And it does seem to be a fairly significant amount — a couple points of blood pressure doesn’t seem like much, but it definitely adds up over time,” he continued.

“It’s really more about understanding what other environmental factors contribute to blood pressure — I think that’s where the next steps need to be,” Dr. Ni added. “We have to have greater awareness of how day-to-day activities and day-to-day exposures for people living their normal lives might impact health factors that contribute to cardiovascular disease.”