Study Suggests Breathing Problems Spike on Hot Days

Hospitalizations for respiratory problems rise on hot, humid days — foretelling what global warming may bring — a study of 12 European cities suggests.

The study, which tracked weather data and hospital admissions over several years, found that on days when a city's temperature approached its typical maximum, hospital admissions for respiratory causes tended to spike.

Adults age 75 and older appeared particularly vulnerable, the researchers report in the American Journal of Respiratory and Critical Care Medicine.

The findings are important, the researchers write, because climate change is expected to increase "extreme weather events" and boost air pollution — which could exacerbate respiratory ills like chronic obstructive pulmonary disease (COPD).

For the study, researchers led by Dr. Paola Michelozzi of the Local Health Authority in Rome used weather data collected over at least three years to calculate a "maximum apparent temperature" for each city. The measure was based on both temperature and humidity.

In most of the dozen cities, the researchers found, hospitalizations for breathing problems increased when the temperature went beyond 90 percent of a city's maximum apparent temperature.

Click here to read an alternate point of view: "Why Are Allergies, Asthma Worse in the Winter?"

Among elderly adults in Mediterranean cities, hospital admissions rose by 4.5 percent for each degree increase beyond the 90-percent threshold, Michelozzi and her colleagues found. That figure was 3 percent in Northern European cities.

Hospital admissions for respiratory causes included infections, such as the flu and pneumonia, and flare-ups of chronic conditions like asthma and COPD — which includes emphysema and chronic bronchitis.

Worsening COPD is a common cause of hospitalizations among the elderly, the researchers point out. Excessive heat, they explain, may create inflammation in the airways, and cause elderly COPD patients to hyperventilate and become breathless.

"Under climate change scenarios," the researchers write, "the increase in extreme weather events and certain air pollutants, especially ozone, are likely to further aggravate chronic respiratory diseases."

They conclude, "Public health interventions should be directed at preventing this additional burden of disease during the summer season."