Why Do More People Die in Winter?

Deaths are not spread evenly across the year. In the United States, they run higher in winter. This article looks at how large the winter peak is and what researchers think is behind it.

How big is the winter peak?

Noticeable, though not huge. The CDC reports that in 2017 an average of 7,708 people died each day in the United States. January had the highest daily average, at 8,478 deaths. February had 8,351 and December had 8,344. The lowest months were June, July, and August, at 7,298, 7,157, and 7,158. By our calculation, that is about 18% more deaths a day in January than in July.

Who dies in winter, and from what?

Mostly older adults, from heart and lung diseases. A study in the journal eLife examined U.S. deaths from 1980 to 2016. It found that deaths among women and men aged 45 and older peaked from December to February. The main causes were respiratory and heart diseases, and injuries. Deaths from heart and lung diseases were highest in January and February and lowest in July and August.

The pattern is different for younger people. Death rates among teenagers and young adults, especially young men, peaked in June and July. Injuries drove those deaths. The study also found that seasonal differences in deaths of young children have largely disappeared.

Is it the cold?

Not clearly. Researchers studied temperature and deaths in 39 cities in the United States and France, as Medical News Today reported. Cities with warmer winters had winter death rates similar to those of colder cities. The authors concluded that temperature is not a key driver of the winter increase. They pointed to other factors that raise the risk of flu and other respiratory infections in winter, such as time spent indoors, school schedules, holiday gatherings, and air moisture.

The eLife study agrees in one way. It found no regional differences in seasonal death patterns, even though U.S. climates vary widely. Other research does link cold weather to many deaths. Medical News Today notes that a study in The Lancet attributed far more deaths to cold than to heat.

Do viruses explain it?

Probably in part. Demographers Tina Ho and Andrew Noymer compared two six-month periods in each year. They found that life expectancy is about one year longer in the summer half, when respiratory viruses circulate much less. They also noted that deaths directly caused by cold, such as hypothermia, are rare. Even so, they argued that a perfect flu vaccine would lower winter deaths by much less than people often assume, because more than flu is involved.

What do researchers still not know?

Why heart deaths rise in winter. Ho and Noymer say the pathways are incompletely understood. Researchers have suggested that respiratory viruses and heart conditions interact, but that has not been proven. No single explanation has been shown to account for the whole peak.

Where can I learn more?

See What Are the Leading Causes of Death in the United States? and What Is the Most Common Age to Die in America?.