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11-03-2013 | General practice | Article

Temperature peaks trigger elderly respiratory admissions


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medwireNews: US researchers have found that rises in outdoor heat are associated with increased numbers of respiratory hospital admissions among the elderly.

The study of 213 US counties found that for each 10°F (5.5°C) increase in daily temperature, there was a 4.3% increase in the number of respiratory hospitalizations among the over 65s.

"As the prevalence of respiratory conditions and the age of the population continue to increase and global temperatures continue to rise as a result of climate change, the risk of heat-related respiratory disease is also likely to increase," warned author Roger Peng (Johns Hopkins School of Public Health, Baltimore, Maryland) in a press statement.

Hospitalizations for chronic obstructive pulmonary disease increased by 4.7% and for respiratory tract infections by 4.1%, the team reports in the American Journal of Respiratory and Critical Care Medicine.

These relationships remained consistent among men and women and across different age groups. However, the effect of heat spikes was most pronounced in counties that had cooler average summer temperatures.

Peng and colleagues say their findings indicate that the association is not due to exposure to air pollution. While there were small to moderate correlations between temperature and air pollutants across counties, the association between temperature and hospitalizations barely changed when adjusted for pollution levels.

The association between heat and respiratory hospitalization was significant on the day of heat exposure, as well as the following day. The authors also found that cumulative exposure over a week to an average 10°F increase in temperature was associated with a 2.2% increase in respiratory hospitalizations. They say their findings confirm previous reports that same-day heat exposure is most strongly linked to hospitalization, indicating that heat-related hospitalizations do not primarily arise from an increased infection rate caused by people sheltering indoors together from the heat.

Instead, the team suggests that the association is established through the direct effect of breathing in hot air, and could also be compounded by thermoregulatory responses such as increased ventilation and panting.

"While outdoor heat has been shown to increase respiratory mortality, evidence on the relationship between heat and respiratory hospitalizations has been less consistent," explained Peng's Johns Hopkins colleague G Brooke Anderson in a press statement.

"We found strong evidence of an association between outdoor heat and respiratory hospitalizations in the largest population of elderly studied to date," the authors conclude.

By Kirsty Oswald, medwireNews Reporter

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