Summary

Blood pressure is known to vary with outdoor temperature, but it is not known how it changes within different groups of the population. Researchers in Paris have studied elderly people in three different urban populations and found significant increases in blood pressure when the weather is cold. The underlying reasons are not well understood, but may be because of changes in the nervous system. Some cardiovascular events are more common in winter, so it could be important to monitor the blood pressure of elderly people more closely when temperatures are cold.

Introduction

It is already well known that blood pressure tends to vary with season - going up in the winter months. For elderly people, these changes might be more significant because of changes in the blood pressure system occurring with age. This might mean that there is a greater risk of cardiovascular events in the winter. But, till now, the seasonal variation in blood pressure has not been studied in elderly people as a specific group.

What was done

Researchers in Paris measured the relationship between blood pressure and temperature for nearly 9,000 individuals aged 65 or more as part of an ongoing 'three cities' study. Blood pressure was measured once at the start and again two years later. Outdoor temperature on the day of measurement was also recorded.

What was found

Both systolic (top figure) and diastolic (bottom figure) blood pressure differed significantly with the four seasons. Systolic blood pressure decreased with increasing temperature, with an 8mm Hg difference between the highest and lowest temperatures. The biggest differences were seen among those aged 80 or more. High blood pressure was detected among 33 percent of participants in winter and among 23 percent in summer.

What this study means

We cannot say that the drop in temperature actually causes blood pressure to increase directly. But the body does respond to changes in outdoor temperature and the hormone catecholamine is released when the temperature drops to help adaptation. This may lead to blood pressure increase. There may be health impacts, particularly for older people. Stroke and aneurysm are more common in colder weather. Therefore, it might be worthwhile closely monitoring blood pressure and medication among the elderly when it is very cold.

Source

Alpérovitch A, Lacombe J-M et al Archives of Internal Medicine January 2009;169:75-80