Warmer Weather May Send More MS Patients to the Hospital
Presenter: Holly Elser, PhD
Multiple sclerosis (MS) patients may be uniquely susceptible to warm weather changes, worsening their symptoms enough to send them to the hospital.
Heat sensitivity is a well-recognized clinical feature of MS, and many sudden increases in core body temperature can worsen neurologic symptoms. Periods of anomalously warm weather are expected to become more frequent as climate changes globally.
Although the effects of rising global temperatures have been documented consistently for particularly susceptible groups, including patients with cardiopulmonary disease, dementia, and serious mental illness, there is little in the medical literature on the implications of MS patients affected by extremes of heat who may also experience symptoms due to seasonal changes in temperature. “Our study suggests that warming trends could have serious health implications over the long term for people living with MS,” said Holly Elser, PhD, of Stanford University School of Medicine.
Elser and colleagues conducted a retrospective cohort study of MS patients aged 18–64 years in a nationwide patient-level commercial and Medicare Advantage claims database. Based on previously validated algorithms, 106,225 MS patients were identified as those with at least three MS-related claims for inpatient, outpatient, or disease-modifying therapy claims within a 365-day period. Anomalously warm weather was defined as any month in which local average temperatures were higher than the long-term average temperature for that month by at least 1.5 degrees Celsius.
In adjusted generalized log-linear models, warm weather anomalies were primarily associated with acute care visits among MS patients. The researchers found increased risk of emergency department visits (relative risk [RR] = 1.04, 95% CI: 1.03–1.06) and inpatient visits (RR = 1.03, 95% CI: 1.01–1.055) related to MS. Effect estimates were similar for men and women and exhibited substantial regional and seasonal variation.
Researchers estimated that over the course of follow-up, periods of anomalously warm weather were associated with an estimated excess of at least 592 emergency department visits, 1,260 inpatient visits and 1,960 outpatient visits related to MS. “While the relative increase in risk of visits is small, the associated absolute effect on people with MS and the health care system is meaningful,” said Elser.
The strongest effects were among older individuals. “The strongest, most precise association was detected among individuals aged 56–64. This may be a function of the accrual of disabilities related to MS as the disease progressed, or accrual of comorbidities,” said Elser.
“In general, our results underscore a point made previously in the literature about the importance to recognize that some individuals may be uniquely susceptible to changes in the environment based on preexisting conditions. More specifically, periods of anomalous warm weather may precipitate acute care visits among MS patients.”
Anomalous warm weather is not limited to temperature extremes typically observed in the summer and early autumn, but may capture indolent changes that can occur even in winter. Healthcare professionals can play a role in advising patients to take precautions when weather is warmer than expected, she said.
The study has two limitations. The analysis did not include direct measures of MS symptoms, disease burden, or disabilities, but instead relied on healthcare encounters. Also, it did not record individual socioeconomic demographics, such as occupation, household income, housing, or race/ethnicity.
Link to abstract: Anomalously Warm Weather and Acute Care Visits in Patients with Multiple Sclerosis: A Retrospective Study of Privately Insured Individuals in the U.S.
Holly Elser, PhD, has nothing to disclose.