Cardiovascular disease-related hospital admissions jump on second day after major snowfall

Person shoveling the snow in winter

For immediate release: Monday, January 30, 2017

Boston, MA – Hospital admissions for cardiovascular diseases decline on days with major snowfalls compared to days with no snowfall, but they jump by 23% two days later, according to a new study led by researchers from Harvard T.H. Chan School of Public Health.

“With global climate change, major snowstorms may become more frequent and severe,” said lead author Jennifer Bobb of the Group Health Research Institute in Seattle, who worked on the study as a postdoctoral researcher in the Department of Biostatistics at Harvard Chan School. “Understanding trends in hospitalizations related to snowfall will help us develop ways to protect public health during harsh winter conditions.”

The study was published online January 30, 2017 in the American Journal of Epidemiology.

The researchers analyzed data for 433,037 adults hospitalized at the four largest hospitals in Boston (Beth Israel Deaconess Medical Center, Brigham and Women’s Hospital, Boston Medical Center, and Massachusetts General Hospital) during the months of November through April, for the years 2010–2015. They focused on admissions for cardiovascular diseases; cold-weather related conditions such as frostbite; and falls and injuries.

“This was a complex data science endeavor that required coordination and linkage of electronic medical records across hospitals,” said senior author Francesca Dominici, professor of biostatistics and senior associate dean for research at Harvard Chan School.

Other findings included:

  • Cold-weather-related disease admissions increased by 3.7% on high snowfall days (greater than 10 inches of snow), compared to days with no snowfall.
  • Cardiovascular disease admissions were higher on days of moderate (5 to 10 inches), rather than high, snowfall.
  • Admissions for falls increased 18% on average during the six days following a moderate snowfall, compared to days with no snowfall.

Health hazards posed by snowfalls may have previously been unrecognized, according to the researchers. A possible explanation could be that people who are most susceptible to cardiovascular events and falls stay indoors during heavy snowfalls and avoid potential hazards, say the researchers.

They write that the two-day delayed jump in admissions for cardiovascular events after heavy snowfalls could reflect delays getting to the hospital during snow emergencies.

The mechanisms by which snowstorms lead to adverse cardiovascular events that are not fully understood, noted the authors. Snow shoveling may be one such factor. This possibility derives from prior studies of “snow-shoveler’s infarction,” which found that heavy snow shoveling resulted in cardiorespiratory demands that were comparable to or higher than the demands of maximal treadmill testing.

This study was supported by the National Institutes of Health (Grants R21 ES022585-01, R21 ES024012, R01 ES024332, R01 ES026217, P30 ES000002, P50 MD010428, K08 AR060257); the Environmental Protection Agency (Grant 83587201-0); the Health Effects Institute (Gran 4953-RFA14-3/16-4); and the Harold and Duval Bowen Fund.

“Time-Course of Cause-Specific Hospital Admissions During Snowstorms: An Analysis of Electronic Medical Records from Major Hospitals in Boston,” Jennifer F. Bobb, Kalon K. L Ho, Robert W. Yeh, Lori Harrington, Adrian Zai, Katherine P. Liao, Francesca Dominici, American Journal of Epidemiology, online January 30, 2017, doi: 10.1093/aje/kww219

For more information:

Marge Dwyer
Harvard T.H. Chan School of Public Health


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Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people’s lives—not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America’s oldest professional training program in public health.