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SYNOPSIS: In a review and meta-analysis of the effects of running and longevity, researchers concluded that running provides specific and significant health benefits and proposed a threshold above which more running provides diminishing returns.
SOURCE: Lee DC, Brellenthin AG, Thompson PD, et al. Running as a key lifestyle medicine for longevity. Prog Cardiovasc Dis 2017;60:45-55.
The roots of running as a sport are deep, dating back to ancient Greece and the original Olympic Games.1 In 1896, the first organized marathon was run at the first modern Olympic Games. This race was created with a nod to the myth of Pheidippides, an ancient Greek long-distance running courier. According to legend, Pheidippides ran 25 miles from Marathon to Athens carrying news of victory in battle but died just after his proclamation, making him perhaps one of the most famous cases of sudden death associated with running.2 Today, we know that physical activity is linked with a number of significant health benefits, including a reduction in all-cause mortality. Investigators are studying the intensity and type of exercise needed to maximize benefits as well as any adverse effects of intensive physical activity.3
In 2014, Lee et al published a study involving running, all-cause mortality, and cardiovascular mortality in more than 55,000 adults. The results pointed to a reduction in mortality with even minimal levels of running.4 To address unanswered questions from the original 2014 study, Lee et al reviewed other related studies and conduct a meta-analysis. Among the stated goals of this comprehensive work were the following: review the effect of running on specific health conditions and longevity; explore the specificity of running vs. other physical activities to health; explore mechanisms behind the health benefits; quantify any additional life expectancy associated with running; and investigate any evidence linking attenuation of health benefits with higher rates of running.
The Effect of Running on Longevity and Specific Health Conditions. The results in Table 1 were drawn from pooled results of five large studies published between 2008 and 2016. Adjustment for age and sex was followed by adjustment for multiple variables, including smoking, alcohol use, socioeconomic factors, and body mass index; adjustment for these multiple variables does not significantly affect results.
Running vs. Other Types of Physical Activity. The first results are drawn from results from the original group of more than 55,000 adults (most of whom were white, non-Hispanic) in the 2014 Lee et al study. To analyze specific health benefits from running compared to other forms of exercise, the data were re-analyzed and divided into four categories: inactive non-runners (reference group); active non-runners; solely runners inactive in other physical activities; and runners active in other physical activity. (See Table 2.)
Data collected from more than 44,000 men in the Health Professionals Follow-up study were consistent with these results with only running, brisk walking, and tennis, revealing an inverse association with cardiovascular disease risk. A British study of more than 80,000 men and women reported a reduction of mortality and cardiovascular disease only in association with swimming, racquet sports, and aerobics but not with running or cycling.
Proposed Mechanisms. Multiple studies have reported associations between robust exercise of any type and mitigation of chronic disease risk factors, such as hypertension, hypercholesterolemia, glucose regulation, and bone density. However, cardiorespiratory fitness (CRF) is emerging as the most strongly predictive factor associated with lowering of mortality. Lee et al noted that running enhanced CRF and found this association was key in understanding the health benefits of this exercise. A meta-analysis of 49 studies (all randomized, controlled trials) covering more than 2,000 adults found that after one year, runners showed improvements in CRF and lipid profile when matched with inactive peers. After adjusting for CRF, the mortality benefits of running were not significant. One of the studies showed a significant association between reduced adiposity and improved CRF in runners compared to energy expenditure equivalent to other forms of physical activity.
Life Expectancy of Runners. The authors of several large studies concluded that after adjusting for multiple factors, the life expectancy of runners is increased by an average of three years when compared with non-runners. This is similar to the mortality benefits found for persons engaging in other forms of physical activity when meeting the minimum recommended threshold of 150 to 229 minutes per week of brisk walking.
Attenuation of Health Benefits. Excessive endurance exercise has been linked to potential adverse health events, such as increased inflammation and cardiac structural changes. Lee et al looked at three studies to compare results regarding “dosage” of running as well as address concerns of the potential adverse effect of running with increases in frequency and intensity.
In all three studies, longevity benefits of running were flattened at the highest levels of running. In two smaller studies, there did seem to be a higher risk of mortality associated with the highest level of running. However, in the largest study,4 no such association was found when comparing the highest frequency running group of > 4.5 hours/week with the lowest of < 51 minutes/week. To calculate an upper limit of running beyond which there are no noticeable health benefits, Lee et al extracted data from at least three large studies from the United States and Britain. The suggested upper limit of running is up to 4.5 hours or 30 miles weekly with at least one day off.
Public interest in these results was widespread, with articles appearing in GQ (“Science: Running Is Better Than Every Other Exercise”5) to Runner’s World (“Experts: Surprisingly Little Running Extends Lifespan”6) to The New York Times (“An Hour of Running May Add 7 Hours To Your Life”7). Although these publications need headlines to attract attention, our job as physicians and clinicians requires a different slant — interpreting the research in a clinically relevant, factual manner to educate patients and enable informed decision-making.
What can we tell patients regarding this comprehensive review and meta-analysis? Clearly, evidence for a link between physical activity and health is compelling. When discussing running, in particular, it is important to note that most of the studies were observational and the quantity of running was based on self-reporting. Thus, associations may be drawn, but we are not yet able to prove causation. Future randomized trials with objective measurable interventions are necessary.
The association with CRF and longevity is interesting. Lee et al noted that CRF improvement may be the most important factor in the link between running and longevity. If so, it would be useful to understand the extent to which other active pursuits increase CRF and if these are associated with a significant increase in longevity. Hopefully, future studies will delve into this relationship.
Understanding the benefits of specific forms of physical activity on health parameters certainly will advance this field and allow firm recommendations for patients. With relatively low cost, easy accessibility, and significant health benefits, running has the potential for clear public health effect. However, studies must be conducted under a variety of conditions and move from a relatively homogenous sample population to diverse gender, racial, socioeconomic, and ethnic groups.
Lee et al mentioned that increases in frequency of running often were accompanied by injury, which limits further running, even temporarily. Also noted was that running activity decreased with age. Studies of other physical activities that carry health benefits equivalent to running could address both of these problems.
Providers can tell patients that strong evidence exists linking physical activity to longevity, and, running in particular, to cardiovascular health and lower cancer mortality. These authors found a significant decrease in all-cause mortality risk for “active” runners who engaged in other physical activity in addition to running; this is clear evidence in support of active lifestyle for all ages. Equally important is the idea of balance and limits; even with exercise, more is not always better and may lead to diminishing or negative returns. The level of running associated with health benefits is unclear, but evidence suggests that even incremental changes in activity level may be significant — a welcome message to patients who find the prospect of running intimidating. In our role as healthcare providers, we are well situated to convey to patients the findings, nuances, subtleties, and limits to current research and assist with incorporating these results into personalized wellness plans.
Financial Disclosure: Integrative Medicine Alert’s Executive Editor David Kiefer, MD; Peer Reviewer Suhani Bora, MD; AHC Media Executive Editor Leslie Coplin; Editor Jonathan Springston; and Editorial Group Manager Terrey L. Hatcher report no financial relationships relevant to this field of study.