Dysnatremia in a changing climate: A global systematic review of the association between serum sodium and ambient temperature

OBJECTIVE

Both hyponatremia and hypernatremia have been reported to occur more frequently with higher ambient temperatures, although the underlying mechanisms are not well understood. Global temperatures are rising due to climate change, which may impact the incidence of dysnatremia worldwide. We aimed to identify, collate and critically appraise studies analyzing the relationship between climate measures (outdoor temperature, humidity) and serum sodium concentrations.

DESIGN

Systematic review, reported in accordance with PRISMA guidelines.

METHODS

MEDLINE and Embase were searched with relevant key terms. Studies assessing the effect on serum sodium measurement of elevated temperature or humidity versus a comparator were included.

RESULTS

Of 1466 potentially relevant studies, 34 met inclusion criteria, originating from 23 countries spanning all inhabited continents. The majority (30 of 34, 88%) reported a significant association between outdoor temperature and dysnatremia, predominantly lower serum sodium with increased ambient temperature. Humidity had a less consistent effect. Individuals aged above 65 years, children, those taking diuretics and antidepressants, those with chronic renal impairment or those undertaking physical exertion had increased vulnerability to heat-associated dysnatremia. The risk of bias was assessed to be high in all but four studies.

CONCLUSIONS

Higher ambient temperature is consistently associated with an increased incidence of hyponatremia. We infer that hyponatremia presentations are likely to rise with increasing global temperatures and the frequency of extreme heat events secondary to climate change. Evidence-based public health messages, clinician education and reduction in fossil fuel consumption are necessary to reduce the expected burden on healthcare services worldwide.

Where do you live and what do you do? Two questions that might impact your kidney health

In many cases the social determinants of health need to be assessed through their interaction with environmental factors. This review looks at the impact of physical location and occupation of individuals on their kidney health. It examines the effect of living at high altitude on kidney function and the relationship between extreme cold or hot temperatures and the incidence of kidney injury. It reviews as well the many occupations that have been linked to kidney disease in high-income and low-and-middle-income countries. As a conclusion, this overview proposes preventive recommendations that could be individualized based on weather, altitude, socio-economic level of the country and occupation of the individual.

The effect of ambient temperature on blood pressure of patients undergoing hemodialysis in the Pantanal-Brazil

The objective was to analyze the association of changes in pre-dialysis systolic and diastolic blood pressure with air temperature in a municipality in the Brazilian Pantanal, a tropical climate area. Longitudinal panel study, with analysis of mixed effects models of 133 hemodialysis patients in the city of Cáceres-Mato Grosso in 2014. Air temperature showed an inverse association with pre-dialysis systolic and diastolic blood pressure. With each increase of 1 °C in the mean air temperature, the pre-dialysis systolic blood pressure decreases -0.730mmHg (p ≤ 0.000) and the pre-dialysis diastolic blood pressure decreases -0.280mmHg (p ≤ 0.000). The estimated effect was greater for systolic blood pressure, but both pre-dialysis blood pressure measures are reduced with an increase in lag (up to two days), even when adjusted for relative air humidity. Air temperature is determinant for changes in pre-dialysis systolic and diastolic blood pressure in hemodialysis patients. The temperature effect was greater for systolic blood pressure than for diastolic blood pressure.

High Water Evaporation Rate is Associated with Low Blood Pressure in Chronic Peritoneal Dialysis Patients

Background

The relationship between water evaporation rate (WER) and blood pressure (BP) in continuous ambulatory peritoneal dialysis (CAPD) patients has not been addressed before. This study was undertaken to evaluate the effects of WER on the BP and body weight (BW) of end-stage renal disease patients treated with CAPD.

Methods

Based on mean WER of each month, the year 2005 was divided into “high WER” and “low WER” stages. This study enrolled 66 CAPD patients at our center during 2005. The BP and BW of each patient were collected monthly. WER was measured with a class A evaporation pan.

Results

Compared to the high WER stage, CAPD patients had higher BP (systolic: 142 ± 29 vs 134 ± 27 mmHg, p < 0.001; diastolic: 86 ± 17 vs 84 ± 16 mmHg, p < 0.001) and BW (56.8 ± 10.2 vs 56.1 ± 10.2 kg, p < 0.001) in the low WER stage. Ambient temperature was significantly higher in the high WER stage ( p = 0.004) and it was also positively correlated with WER ( r = 0.82, p = 0.0012). Both mean BP ( r = –0.72, p = 0.0089) and BW ( r = –0.79, p = 0.002) showed inverse relationships to the WER. Moreover, both mean BP ( r = –0.95, p < 0.001) and BW ( r = –0.90, p < 0.001) also showed negative linear regressions to ambient temperature. There was a positive linear regression between mean BP and BW ( r = 0.85, p = 0.0004). Multiple linear regression analysis found that WER (β = –0.672, p = 0.026) was an independent factor correlated to patients’ mean BP.

Conclusions

CAPD patients had lower BP and BW in the high WER stage. These decreases were associated with higher ambient temperature and WER. We hypothesize that increased insensible salt and fluid loss secondary to high WER during hot seasons, especially in subtropical areas, ameliorates the hypervolemia and hypertension in CAPD patients.