NEW YORK, Dec 24 (Reuters Health) -- Patients who experience cardiac
arrest during the winter have significantly lower survival rates than patients
whose heart attacks occur during the summer months, researchers report.
Based on the findings, the study authors recommend that at-risk heart
patients living in colder climates take simple precautions such as ensuring
"adequate indoor heating, wearing protective clothing, especially outdoor
protection of the face, and avoiding unaccustomed strenuous exercise."
Previous studies have suggested that rates for stroke and heart attack
rise during the cold winter months.
In their latest study, researchers led by Dr. J.P. Pell, of the Greater
Glasgow Health Board in Scotland, compared 1988-1997 data on nearly 11,000
Scottish patients suffering cardiac arrest. Half of the cardiac arrests occurred
in winter, while the other half occurred during the summer months.
The authors report that the prognosis of patients who suffered cardiac
arrest during the winter was poorer than for those who experienced the event
during the summer -- even after adjusting for risk factors such as age or
whether or not the patient received cardiac defibrillation to start their
hearts. Overall, patients who experienced arrest during winter were 19% less
likely to survive to hospital discharge, compared with patients treated during
the summer.
Declines in body temperature may account for the seasonal decline in
survival rates, the investigators speculate. They point out that lower ambient
temperatures increase blood viscosity ('stickiness'), while a "generalised
cooling of the body increases blood pressure and cardiac output." In fact,
recent research has suggested that wintertime cooling can increase blood
pressure by an average of 5 mm Hg compared with readings taken in summertime.
Other factors contributing to increased cold-weather risks may include
reductions in blood levels of vitamin D, higher blood cholesterol levels, and a
general tendency to increased body weight during the colder months, according to
the researchers.
So what can individuals do to reduce wintertime heart risks? Pell and
colleagues acknowledge that a move to a warmer climate is "not an option" for
most heart patients. However, they believe that "simple precautions" -- such as
adequate heating, wearing scarves and hats to warm the head and face, and
avoiding "unaccustomed strenuous exercise -- can raise wintertime body
temperatures and help protect heart patients.
