Researchers examine extreme heat, multiple sclerosis link

August 09, 2021
New findings suggest clinical visits by multiple sclerosis patients increased during months linked to warmer weather and high humidity. The findings could guide region-specific strategies to manage MS, such as providing heat advisories and critical information on sudden changes in local weather to MS patients and healthcare providers.

In a recent study, researchers at the University of Miami’s Miller School of Medicine found that between January 2010 and December 2013, the number of clinical visits by MS patients to the nation’s Veterans Affairs medical centers increased substantially during months associated with warmer weather, soaring humidity rates, and huge temperature swings, with visit rates varying across different regions of the country.

The highest frequency of MS clinic visits occurred in March (an 8.9 percent increase), followed by August (8.8 percent). Winter months, on the other hand, saw relatively low rates of MS clinic visits, with December (7.7 percent) recording the lowest.

Across geographic regions, the Pacific Northwest saw the highest MS clinic visit rate (67.6 per 10,000 patient visits), followed by the Northeast (64 per 10,000) and the subtropical U.S. (46.8 per 10,000 patients). The lowest MS clinic visit rates, Kumar noted, were observed in the Lower Midwest (15.1 MS clinic visits per 10,000 patients), followed by the Upper Midwest (24.6 per 10,000). 

Temperature variability, or the rate at which temperature changes day-to-day or month-to-month within a single year, most likely had an effect on increased rates of clinical MS visits.

For the study, researchers relied on Veterans Affairs medical data, reviewing the clinical visits of a total of 27,290 patients with MS, many of whom had multiple doctor appointments at VA health care facilities during the study period. Most of the subjects were white, non-Hispanic males (75.2 percent), followed by Black males (18.3 percent). 

The group also used meteorological data from the National Climactic Data Center for the period 2009 to 2014.

The researchers said patients with MS should consider regulating their indoor temperature and avoiding exposure to unstable outdoor weather conditions when possible. They stressed this study focused on the clinical visits of a specific group of patients — veterans — and further investigation into the link between weather-related heat and worsening symptoms of MS should be pursued.

The findings were published in the International Journal of Environmental Research and Public Health.

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