Heart Disease. It is the leading cause of death in the United States, taking over 600,000 American lives each year, surpassing all cancers combined. The fast paced American life-style filled with long hours of work and financial stress combined with a fast food based diet and substantial screen time (T.V., phones, tablets) leaves the average American with little to no time to exercise. A sedentary lifestyle is all but to blame for this disease.
Is heart disease preventable? Of course it is. In addition to eating a healthy and balanced diet, aerobic and cardio exercise has proven to be beneficial in maintaining cardiovascular health. It has been demonstrated that just 30 minutes of moderate exercise a day can have a substantial impact on reducing the risk of heart disease.
Numerous studies have established that those who partake in aerobic activities, such as running, live longer and healthier lives. Running is a very efficient method of exercise for increasing heart rate and burning a high number of calories in a short period of time. Furthermore, new research shows that doing the exact opposite, such as sitting on the couch or behind a computer for long periods of time, has the opposite effect and can substantially increase an individual’s risk of heart disease.
But can too much of a good thing be bad? Yes and no. Running is considered a high impact sport and can therefore lead to joint damage after a long period of time – but this is a well-known fact. Musculoskeletal injuries are nothing new to those who run on a daily basis, especially many of whom train for longer distances such as half (13.1 miles) or full marathons (26.2 miles).
We often think of marathon runners as the epitome of health and fitness. Running a marathon is a common item on many of our bucket lists. As a challenging feat, a marathon takes dedication and time, not to mention the accompanying pain, sweat, and tears. A marathon not only brings a sense of self-satisfaction but can also be a critical point in an individual’s well being and their endeavors to turn their life around.
On the other hand, new research from Yale University has raised concerns about this activity and may discourage many of us from partaking in such a challenge. Scientists under the direction of Sherry G Mansour DO found that marathon runners were 82% more likely to develop Acute Kidney Injury after running a marathon. This number is quite unexpected, as acute kidney injury is an event that more commonly takes place in high-risk hospital patients undergoing life-threatening procedures, such as open-heart surgery. Eighty two percent of marathon runners develop acute kidney injury, compared to only 52% of invasive heart surgery patients. Additionally, microscopy urine analysis demonstrated that 73% of the runners who have urine sediments, an indication for acute tubular injury.
However, before we dive too deep into the details, let’s first discuss Acute Kidney Injury, also known as AKI. The “acute” part of the disease refers to damage that takes place in a short period of time, ranging from hours to a couple of days. This injury to the kidneys usually takes place as a result of the accumulation of waste products in the blood. The kidneys experience much difficulty in attempting to maintain a balance of fluids within the body, which can lead to organ damage. AKI is most common in older hospitalized patients under intensive care or in patients following extensive surgery.
Prior to this study’s finding of AKI in marathoners, the list of most common reasons for developing AKI included:
Low blood pressure (“hypotension”) or shock
Blood or fluid loss (such as severe diarrhea and bleeding)
Heart attack, heart failure, and other conditions leading to decreased heart function
Overuse of pain medicines or “NSAIDs” intended to decrease inflammation or alleviate discomfort from headaches, flu, soreness, and other ailments. Examples include ibuprofen (Advil), and naproxen (Aleve).
Severe allergic reactions
Researchers followed 22 marathoners, examining their kidney function using tests that measure their creatinine, urine albumin, and injury and repair-related biomarkers. All of the runners were examined the day prior to the race, the day of the race, and 48 hours following the race. Strikingly, 18 of the 22 runners had positive test results pointing to an AKI diagnosis immediately following running 26.2 miles on race day.
Participants analyzed in this study included veteran runners (56% women) with an age range of 22 to 63 years (mean age, 44 years). In order to be included in this study, participants had to have a normal body mass index (18.5 to 24.9 kg/m2), in addition to running at least 15 miles a week on average for the previous 3 years.
Runners who had sustained extensive injuries from running within the previous 4 months, or had participated in any other marathons prior to the Hartford Marathon, were excluded from the study. Subjects were also prohibited from using any NSAIDs 48 hours prior and 24 hours following the marathon.
In this specific study, a 24-hour urine sample was collected prior to the marathon, immediately after, and 24 hours after. The researchers analyzed a regular panel of tests, which included serum creatinine, creatine kinase and urine albumin. This study is unique due to the analyses of several markers of kidney injury found in the urine, such as interleukin-6 and interleukin-18 and kidney repair such as YKL-40. Additionally, neutrophil gelatinase-associated lipocalin (NGAL), a novel urinary biomarker, was utilized in this study, which has been identified as an AKI indicator.
However, all 22 runners with AKI had normal functions when tested 48 hours later, further confirming that this was an acute injury that resolved on its own. The authors presume that the cause of the kidney damage is secondary to a combination of events that takes place when a person runs a marathon.
During this time period, the body loses a high volume of water and can become dehydrated. In addition to dehydration, micro-damage to the runners’ muscles, which is caused by the high-impact nature of running, releases byproducts within the blood that then go through the kidneys’ filtration system. However, post-running, runners (usually) rest and rehydrate, causing these signs go away.
So what does this all mean? Well, not a whole a lot, other than the fact that AKI is a common occurrence that is witnessed in runners immediately following a marathon. However, to make generalizations in order to recommend for or against running would be rather unscientific.
Analyzing the acute event, we learn that 100% of the individuals in this study had their kidney function levels return to normal within 48 hours. Whether running marathons impacts the kidneys of runners in a chronic fashion is a question that this study does not attempt to answer. In order to do so, a large cohort of runners would have to be tracked over a long period of time, and a number of factors would need to be recorded and taken into consideration.
Such a study would require basic demographic information such as age, gender, ethnicity, weight, baseline health, and an extensive medical history (including a family history of chronic illnesses). Furthermore, not only does the frequency of marathon runs need to be taken into account, but also the location, time of year, hydration techniques , in addition to the runners’ training regimens, need to be considered as well . These requirements are far more extensive than the approach this study took.
But what can we conclude from the information that we have? It is fair to say that, for the long-distance runners, the following checklist may serve as a baseline guideline based on the results of the findings. However, keep in mind that your personal physician should be consulted prior to making any drastic changes to your training approach. Regardless, here are a few general takeaways in order to reduce the risk for chronic kidney disease:
1. Hydrate, Hydrate, Hydrate!
Water intake is by far the most important item on the list for runners in order to prevent volume depletion. Sports drinks are a good substitute, especially if they contain sugar, sodium, and potassium, which is essential for water intake from the gut.
2. Recovery time is key
Even with hydration, AKI may continue to take place; it is unwise to partake in another long run prior to allowing time for recovery. This study’s suggestion is to wait around 48 hours, which may be a good starting point.
3. No NSAIDs
Although anti-inflammatory drugs can be a runner’s best friend, they tend to decrease blood flow to the kidneys, further increasing the stress and burden on these delicate organs as you push yourself through 26.2 miles of running. If you must have your ibuprofen, it is important that it is done so after the race, having fully rehydrated prior to consumption.
4. Listen to your body.
As cliché as it may sound, pushing through the pain is one thing while ignoring important signals is another. Watch for signs of dehydration on hot days, as it can happen even though a runner may think that they have had plenty to drink.
So should you stop running in the fear of developing kidney damage? Probably not, but it is important to make this an important reminder to listen to the basic guidelines of running, as well as allowing for complete recovery after a long run or difficult training period. Hopefully, we will know more about this condition as future studies include a larger patient population for longer periods of times, and many more variables are accounted for to fully assess the risk for Acute Kidney Injury.
Yale Study: Mansour et al, Kidney Injury and Repair Biomarkers in Marathon Runners, American Journal of Kidney Diseases, 2017.