Can exercise make us live longer?
If exercise protects against early death - lowering the risk of premature death by 72% compared to inactive individuals - does it also extend lifespan? Can exercise make us live longer? If so, how much and what kind of exercise would?
That is what researchers in Norway had the ambition to answer with Generation 100, the longest and largest randomised controlled exercise trial on exercise to date. In “real-life settings”, the study enrolled over 1500 adults aged 70-77 years to participate in moderate (MICT) or high intensity (HIIT) training twice per week, in addition to exercising according to national guidelines as a baseline. The study required a five-year commitment. The authors were looking at the mortality rate in the study population compared to the general 70-77 year old adults.
How do you maintain participation in higher levels of activity for this long in an elderly population?
First, as you might expect, adherence was lower in the HIIT and MICT groups through the 5 years than in the control group. In fact, the HIIT group barely met the adherence criteria of 50% set by the authors the first year and people in this group kept dropping out over time, such that adherence in HIIT was 47% at 5 years.
In contrast, 78% to 69% of the people in the control group exercising according to national guideline were able to keep up the expected level of activity.
This is despite involving the volunteers in the study through feedback and making adjustments on the reporting frequency. Training was also supervised twice a week, tapping into creating a sense of community with group activities.
In addition, 80% of the people who participated in the study reported to already follow the national guidelines at the time they were enrolled: an extraordinarily high number.
To put things in context, in the UK, only one in four adults over 65 meets the minimum recommended activity levels needed to maintain health. In the US, it is estimated that 28 to 34% of adults 65 to 74 years of age are inactive (2).
The results clearly show that even in such a healthy and active population, less than half of the participants in the HIIT group were able to maintain the highest levels of physical activity at one, three and five years upon enrollment.
Generation 100 also falls short to confirm the hypothesis that higher intensity is beneficial for survival. Although the mortality rate of people participating in the study was 4.6%, compared to 10% in the same age group in the broader population, suggesting that physical activity contributes to living longer, no significant difference was found in mortality between the different groups (only a “trend”).
Figure 1: Mortality rate in the three different exercise intensity groups of the study Generation 100.
The authors acknowledge that the results suffer from a healthy volunteer bias (3, 4 ), which means that other factors than exercise could play into the lower mortality rate of participants in the study.
To muddy the waters even more, “crossover” occurred with 18-23% of the participants from the control group and 11-14% from the MICT group deciding to increase their exercise intensity to match HIIT sessions.
Such crossover blurred the lines between the groups, thus the results of the study. It is also unclear how the data analysis accounted for the crossover.
Even when looking at secondary endpoints of the study such as cardiovascular and cancer deaths, or VO2 max, no difference was found between the groups.
Yet, the authors conclude that higher intensity exercise, in addition to physical activity following to guidelines, contributes to a reduction of mortality in 70-77 year old adults and go as far as suggesting that the guidelines be updated.
This can bring us to ask what guidelines are for. Are they helping people create the minimum requirements for health and longevity, or are they ideal we need to strive for? Although not a conclusion from the authors, this study actually shows that, long term, sticking to the current guidelines (69% adherence at 5 years) is easier for this healthy population between 70 and 77 than increasing the exercise intensity (47% and 51% adherence in the HIIT and MICT group respectively).
Underlying these results is the unanswered question: Is it more beneficial for longevity to establish guidelines 70% of people can stick to consistently or to encourage higher levels of intensity that less than half of a healthy population can maintain?
Given the supervision and community created in the conditions of the study, it is also fair to ask what adherence would be if people had been left to their own device, without this support.
The real takeaways from Generation 100 are found when taking a step back and looking at the results of the study at large. The authors published multiple papers in different journals depending on focus of the journal and the data analyzed.
Taken all together the different conclusions paint a picture that suggests that the overall health and fitness of the participants at baseline is what matters in leading to positive outcomes.
Here’s how: those who were motivated and able to keep with higher intensity for the 5 years of the study were also those with higher VO2 max at inclusion, higher overall cardiorespiratory fitness, and better grip strength and were already physically active when enrolled. They also had higher education, which generally correlates with higher health and wellness. It was also found in this work that those with higher VO2 max at enrollment were the ones whose brain structures were best preserved through the 5 years of the study, with no difference depending on the levels of activity.
Overall, a more honest conclusion to the study is that being fit when turning 70 creates the conditions to stay fit after 70.
Unfortunately, Generation 100 does not help us find out if exercise makes us live longer.
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