Study: Heating Climate Can Lead to Higher Risks of Mortality, Hospitalization in Patients With ESRD

Ambient temperature was found to be associated with reduced blood pressure, interdialytic weight gain (IDWG), and increased risks of mortality and hospitalization for patients with end-stage renal disease (ESRD), according to a recent study.

The findings from the retrospective cohort study, published in Environmental Research, suggested that from a statistical standpoint, blood pressure and IDWG may not entirely explain the relationship of maximum dry-bulb temperature (TMAX) with mortality and hospital admissions.

“This suggests that causes of mortality and morbidity effects may involve other time-varying and time-invariant risk factors, and more complex mechanistic pathways to describe temperature effects specific to the [ESRD] population,” wrote the investigators.

Warming ambient temperatures can cause physiological changes in the general population including renal-related health effects, such as kidney failure, heatstroke, and fluid and electrolyte imbalances, which can lead to hospitalization and mortality among older adults exposed to heatwaves. Additionally, elevated temperature and increased frequency of extreme heat related to climate change can pose a substantial public health threat to individuals with chronic renal dysfunction, including ESRD.

ESRD management involves frequent dialysis treatments and patients with ESRD are more susceptible to life-threatening complications resulting from fluctuations in weight and blood pressure. The accumulation of fluid-based weight gains between hemodialysis treatments, the percentage of which is represented by IDWG, is known to cause increased blood pressure and sudden changes in blood pressure can compromise physiological stability in patients with ESRD.

The investigators set out to understand the role of intermediate effects due to exposure to ambient temperature during warmer calendar months (May to September) within Philadelphia County, Pennsylvania. The study included 1981 patients with ESRD undergoing dialysis treatment at Fresenius Kabi Medical Care clinics from 2011 to 2019. The average monthly relative humidity ranged from 64.9% to 69.2% throughout the study period of each year.

The participants contributed about 4764 person-years collectively. Among the 1981 participants, the investigators observed 934 patients with more than 1 hospital admission and 439 patients with 1 hospital admission. The mean (SD) age of the cohort was 60.1 (14.1) years and 828 (42%) were women.

Clinically measured predialysis systolic blood pressure (preSBP) and IDWG responses to temperature increases were estimated using linear mixed effects models. Lags up to 2 days (lag 2) were considered for TMAX exposure and a 1-day lag (lag 1) was considered for mediator variables before all-cause hospital admission or all-cause mortality events to assure temporality between exposure outcome models.

Based on lag 2 to lag 1 temporal ordering, a 1℃ increase in daily TMAX was associated with a 1.4% increased risk of all-cause hospital admission (adjusted HR [aHR], 1.014; 95% CI, 1.007-1.021) and a 7.5% increased risk of all-cause mortality (aHR, 1.075; 95% CI, 1.050-1.100). Short-term lag exposures to 1℃ increases were associated with mean reductions between 0.013 and 0.015% in IDWG and 0.168 to 0.229 mm Hg in preSBP.

The investigators noted that only 1.03% of the association between temperature and all-cause mortality was mediated through preSBP. The mechanistic path for IDWG alone showed inconsistent mediation and potential reductions in all-cause hospital admission by 15.5% and all-cause mortality by 6.3%. The proportion mediated estimates generated from the pathway that observed preSBP and IDWG collectively achieved a 2.2% and 0.3% increase in combined pathway analysis for all-cause hospital admission and all-cause mortality outcomes, respectively.

The study had several limitations, including that it included only 2 measured mediators; cold-temperature related effects were not examined; and a lack of consideration for clinical measures on dialysis vintage estimated kidney filtration rate and albumin to creatinine ratio.

“The findings from this research could inform potential interventions to minimize the impact of extreme heat among [ESRD] patients,” the investigators said.

Reference

Remigio RV, Turpin R, Raimann JG, et al. Assessing proximate intermediates between ambient temperature, hospital admissions, and mortality in hemodialysis patients. Environ Res. 2021;204(Part B):112127. doi:10.1016/j.envres.2021.112127