PARIS, Jan. 12 -- Old man winter can boost blood pressure in older patients, French researchers found.
Systolic blood pressure among patients 65 and older rose 5.0 mm Hg on average along with a roughly 25° F drop from summer to winter in southern France, reported Christophe Tzourio, M.D., of Hopital La Salpêtrière here, and colleagues in the Jan. 12 issue of the
Archives of Internal Medicine.
In the population-based study, hypertension rates likewise rose from 23.8% to 33.4%, with an even more pronounced effect on those ages 80 and older.
Action Points
- Explain to interested patients that the study supported an effect of outdoor temperature on blood pressure in older adults.
- Notice that the researchers cautioned that the findings might have been limited by a study sample of elderly individuals not representative of the general population.
"During periods of extreme temperatures," Dr. Tzourio's group wrote, "a careful monitoring of blood pressure and antihypertensive treatment could contribute to reducing the consequences of blood pressure variations in the elderly."
Seasonal variations in blood pressure accompanying changing outdoor temperatures through the year have been described in the general population for more than four decades, the investigators said. Aging may increase susceptibility to temperature-related variations in blood pressure because of declining baroreflex control, they added.
To see whether age was a factor, the researchers analyzed findings from 8,801 patients 65 or older in the Three-City Study.
The population-based longitudinal study primarily examined dementia and vascular disease in residents of Bordeaux, Dijon, and Montpellier in France but also included blood pressure measurement twice, about two years apart.
Dr. Tzourio's group found that both systolic and diastolic blood pressure tended to fall in spring and summer months compared with autumn and winter (P=0.14).
These consequences were "not negligible," the researchers noted, with a systolic range from 150.1 mm Hg at the lowest temperature quintile to 142.1 mm Hg at the highest.
Repeat measurements showed the same pattern. When outdoor temperatures were colder on patients' return blood pressure measurements, blood pressure was higher (+2.3 mm Hg systolic for a -15°C difference versus -9.7 mm Hg for a +15°C difference, P<0.001). Diastolic pressure had the same significant trend (P<0.001).
Although the effect was seen in both men and women and those of all age ranges, the changes in blood pressure by temperature were larger after age 80.
For a the same 15°C decrease in outdoor temperature, systolic blood pressure increased 5.1 mm Hg in those age 80 and older compared with 0.8 mm Hg in those 65 to 74. Diastolic pressure acted similarly.
The researchers cautioned that the findings were limited by a sample of elderly patients not representative of the general population. They noted, though, that the results were not confounded by an increase in alcohol intake in winter or of physical activity in summer.
One possible explanation for increased blood pressure could be increased heart rate and peripheral vascular resistance via activation of the sympathetic nervous system and secretion of catecholamine in response to cold temperatures, the researchers suggested.
But although there were small significant variations in heart rate between winter and summer (71.7 versus 70.8 beats per minute), hypertension treatment had no influence on the relationship between blood pressure and temperature.
While the study could not provide a causal link between blood pressure and outdoor temperature, Dr. Tzourio's group concluded that monitoring blood pressure and antihypertensive medication in older patients may be particularly important during extreme weather, hot or cold.
The authors noted that "in our study, as in other studies, blood pressure measurements were made in rooms where temperature in winter is around 20° C. In winter, participants who were examined at home in the morning had usually spent more than 12 hours in warm rooms. This suggests that indoor temperature in its usual range has limited influence on blood pressure."
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| The 3C Study was conducted under a partnership between INSERM, the Victor Segalen-Bordeaux II University, and Sanofi-Aventis. The 3C Study was also supported by the Caisse Nationale Maladie des Travailleurs Salariés, Direction Générale de la Santé, Mutuelle Générale de l'Education Nationale, Institut de la Longévité, Conseils Régionaux of Aquitaine and Bourgogne, Fondation de France, and Ministry of Research-INSERM.
The researchers reported no conflicts of interest. |
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