A study, stretching over almost half a century, shows that physical inactivity is second only to smoking as a risk factor for mortality.

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Physical inactivity was found to be second only to smoking as a mortality risk factor.

Fitness levels have long been known to play an important role in staving off a number of serious illnesses.

At the same time, evidence has been steadily mounting that demonstrates the negative health implications of a sedentary lifestyle.

For instance, a meta-analysis published in the journal Diabetologia in 2012, concluded that:

"Sedentary time is associated with an increased risk of diabetes, cardiovascular disease, and cardiovascular and all-cause mortality."

Similarly, another meta-analysis, published in PLOS One in 2013, measured the amount of daily sitting time and how it impacts on mortality; they concluded:

"Higher amounts of daily total sitting time are associated with greater risk of all-cause mortality and moderate-to-vigorous physical activity appears to attenuate the hazardous association."

Charting fitness and mortality

Against this backdrop of research, the current study approaches the question from a slightly different and more direct angle. In one of the longest studies of its type, published in the European Journal of Preventive Cardiology, researchers investigated fitness levels and their effect on lifespan over the course of almost half a century.

A team - led by Dr. Per Ladenvall from the Department of Molecular and Clinical Medicine, Sahlgrenska Academy at the University of Gothenburg, Sweden - used data from the "Study of Men Born in 1913." In total, 792 men were followed for 45 years. The participants were all 50-year-old men when they were recruited in Gothenburg in 1963.

The researchers designed the study to investigate the risk factors for cardiovascular disease and mortality.

In 1967, the group's members all completed an exercise test; additionally, 656 of the cohort carried out a maximum exercise test where they were required to push themselves to the limit (the others were exempt due to health concerns that might have made the exertion dangerous).

Some of the participants in the maximum exercise group also had their maximal oxygen uptake (VO2) measured using ergospirometry - a way to continuously measure respiration and gas metabolism during exercise.

Roughly once every 10 years, up until 2012, physical examinations were performed. Information regarding cause of death was obtained from the National Cause of Death Registry.

VO2 max and mortality

In order to analyze the association between VO2 max and mortality, the men were split into three sections (tertiles). They were arranged from low to high - 2.00 liters per minute, 2.26 liters per minute, and 2.56 liters per minute.

A clear pattern emerged: each tertile increase in VO2 max predicted a 21 percent lower risk of death over the 45-year course of the study. This effect remained significant after controlling for blood pressure, smoking, and serum cholesterol levels.

"We found that low aerobic capacity was associated with increased rates of death. The association between exercise capacity and all-cause death was graded, with the strongest risk in the tertile with the lowest maximum aerobic capacity. The effect of aerobic capacity on risk of death was second only to smoking."

Dr. Per Ladenvall

Over recent years, as Dr. Ladenvall notes, great strides have been made in reducing the number of smokers. The next challenge is to encourage people to get active and stay active.

The study is unique because of the long length of its follow-up; the duration of the study means that there is a wealth of data to mine. Medical News Today asked Dr. Ladenvall if he has plans to analyze any other aspects of the dataset. He said: "In a next step, we are planning to do analyses on fatal and non-fatal cardiovascular events such as myocardial infarction and stroke."

When MNT asked what follow-ups Dr. Ladenvall is planning, he advised that this was just the first in a "series of population-based cohorts in Gothenburg." The next datasets will also include women, allowing the researchers to see whether the current results are relevant for both genders.

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