The physical stress of running a marathon can cause kidney injury, although kidneys of the examined runners fully recovered within two days, according to a Yale study.
The study raises questions concerning potential long-term impacts of this strenuous activity at a time when marathons are increasing in popularity.
More than a half million people participated in marathons in the US in 2015. While past research has shown that engaging in unusually vigorous activities – such as mine work, harvesting sugarcane, and military training – in warm climates can damage the kidneys, little is known about the effects of marathon running on kidney health.
A team of researchers led by professor of medicine at Yale University Dr Chirag Parikh, studied a small group of participants in the 2015 Hartford Marathon. The team collected blood and urine samples before and after the 26.2-mile event. They analysed a variety of markers of kidney injury, including serum creatinine levels, kidney cells on microscopy, and proteins in urine.
The researchers found that 82% of the runners that were studied showed Stage 1 Acute Kidney Injury (AKI) soon after the race. AKI is a condition in which the kidneys fail to filter waste from the blood. "The kidney responds to the physical stress of marathon running as if it's injured, in a way that's similar to what happens in hospitalised patients when the kidney is affected by medical and surgical complications," said Parikh.
The researchers stated that potential causes of the marathon-related kidney damage could be the sustained rise in core body temperature, dehydration, or decreased blood flow to the kidneys that occur during a marathon.
While the measured kidney injury resolved within two days post-marathon, the study still raises questions about the effects of repeated strenuous activity over time, especially in warm climates.
"We need to investigate this further," said Parikh. "Research has shown there are also changes in heart function associated with marathon running. Our study adds to the story – even the kidney responds to marathon-related stress."
Abstract
Background: Investigation into strenuous activity and kidney function has gained interest given increasing marathon participation.
Study Design: Prospective observational study.
Setting & Participants: Runners participating in the 2015 Hartford Marathon.
Predictor: Completing a marathon.
Outcomes: Acute kidney injury (AKI) as defined by AKI Network (AKIN) criteria. Stage 1 AKI was defined as 1.5- to 2-fold or 0.3-mg/dL increase in serum creatinine level within 48 hours of day 0 and stage 2 was defined as a more than 2- to 3-fold increase in creatinine level. Microscopy score was defined by the number of granular casts and renal tubular epithelial cells.
Measurements: Samples were collected 24 hours premarathon (day 0), immediately postmarathon (day 1), and 24 hours postmarathon (day 2). Measurements of serum creatinine, creatine kinase, and urine albumin were completed, as well as urine microscopy analysis. 6 injury urine biomarkers (IL-6, IL-8, IL-18, kidney injury molecule 1, neutrophil gelatinase-associated lipocalin, and tumor necrosis factor α) and 2 repair urine biomarkers (YKL-40 and monocyte chemoattractant protein 1) were measured.
Results: 22 marathon runners were included. Mean age was 44 years and 41% were men. 82% of runners developed an increase in creatinine level equivalent to AKIN-defined AKI stages 1 and 2. 73% had microscopy diagnoses of tubular injury. Serum creatinine, urine albumin, and injury and repair biomarker levels peaked on day 1 and were significantly elevated compared to day 0 and day 2. Serum creatine kinase levels continued to significantly increase from day 0 to day 2.
Limitations: Small sample size and limited clinical data available at all time points.
Conclusions: Marathon runners developed AKI and urine sediment diagnostic of tubular injury. An increase in injury and repair biomarker levels suggests structural damage to renal tubules occurring after marathon. The results of our study should be validated in larger cohorts with longer follow-up of kidney function.
Authors
Sherry G Mansour, Gagan Verma, Rachel W Pata, Thomas G Martin, Mark A Perazella, Chirag R Parikh
[link url="https://www.sciencedaily.com/releases/2017/03/170328145257.htm"]Yale University material[/link]
[link url="http://www.ajkd.org/article/S0272-6386(17)30536-X/abstract"]American Journal of Kidney Diseases abstract[/link]