Heart attack risk higher on cold, windy, grey days: Swedish study

When the weather is bad, more people have heart attacks, Swedish researchers have found.

In a study published in JAMA Cardiology, scientists report that lower temperature, higher wind speeds and less sunshine are all associated with a greater incidence of heart attack.

The link was strongest with temperature. A temperature decrease from 20C to -1C was associated with a 14 per cent increased heart attack risk. As the wind speed increased from 0 to 48 km/h, there was a 7 per cent increase in risk.

And when the hours of sunshine without clouds decreased from 10 hours a day to none, heart attack risk went up by 11 per cent.

The study included 274,029 heart attack patients with complete data on location of the cardiac care unit and time of admission, plus more than 3.5 million data points on weather at each site from 1998 to 2013.

“This is a huge study,” said the senior author, Dr. David Erlinge, a professor of cardiology at Lund University in Sweden, “and the data is very robust.”

The authors propose several possible mechanisms. Flu is associated with heart attack and is more common in winter. Changes in physical activity and diet in colder weather may affect heart health. And depression, which can be caused by reduced hours of sunshine, also increases cardiac risk.