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People are always surprised to learn that there are two functional tests that we perform in our office that are as predictive of longevity as just about any other markers we know. Those tests are the VO2 max fitness test and lean mass by DEXA scan. Not only are they predictive of lifespan, but even more importantly they are predictive of healthspan. We will review both markers in this month’s blog.
Lean Mass
Study after study shows that higher skeletal muscle mass is associated with a lower risk of all-cause mortality. Countless studies have been published demonstrating this finding, and it doesn’t matter what population is examined (various countries, age groups, male vs. female, etc), the results are always the same. Not only is higher skeletal muscle mass predictive of decreased mortality, but it is also associated with a decreased risk of just about every chronic medical condition that has been studied. Whether it’s cardiovascular disease, cancer, dementia and Alzheimer’s disease, type 2 diabetes, or osteoporosis, a higher muscle mass will decrease your risk of developing these conditions. (Important note: links to sources and studies are included at the bottom of this blog).
Muscle mass improves your overall health via a number of mechanisms. Muscle tissue is highly metabolically active and increases your resting metabolic rate. Muscle and bone health are closely linked, and increased muscle mass improves bone strength. In fact, some studies show that in elderly adults muscle mass is more strongly related to the risk of hip fracture than bone density. Muscle also plays a critical role in improving insulin sensitivity, regulating blood sugar, and decreasing chronic inflammation.
How do you increase your muscle mass? There are three primary levers to pull:
- Strength training
- Hormone replacement therapy (in particular testosterone and DHEA)
- Optimal protein intake
An important caveat of the above studies linking lean mass with all-cause mortality is that they are population studies that demonstrate correlation but are not able to prove causation. That is to say, a high muscle mass at baseline is associated with a longer life span, but that does not prove that interventions that increase muscle mass (e.g. strength training) lead to a longer life. We simply don’t have research studies that test this hypothesis, as such studies are exponentially harder and more expensive to perform.
But we do have studies that test whether strength training increases markers that are proximal to longevity, such as cognitive function, which is still an extremely important outcome. And those studies are very encouraging. One study tested 62 adults aged 65–75 years who undertook 24-week resistance training at two intensities to examine the impact of muscle strength training on cognitive function. Participants were randomly assigned to 1 of 3 groups: control, moderate-intensity training, and high-intensity training. The moderate and high-intensity groups experienced improved cognitive function in several domains as measured by the Wechsler adult intelligence scale. Another study evaluated the effect of eight weeks of aerobic strength training on the executive function of 47 healthy adults (mean age 70.7 ± 5.6 years) and reported increased muscle strength and improved executive function.
Most well-designed studies such as these two are ultimately underwhelming due to their small sample size and short duration of therapy. What we really want to know is whether a xxx (insert your age here…45, 55, 65, etc) year old who commits to the interventions that we know increase muscle mass (resistance training, HRT, optimal protein intake) can reliably improve the outcomes that we all care about when we are older: memory, executive function, strength, posture, decreased risk of falls, overall vigor, among many others. Such studies will probably not ever be done, at least not in a randomized, controlled fashion, due to their exorbitant cost and lack of financial incentive. But we can reasonably extrapolate from the knowledge we do have that consistent efforts to increase muscle mass will lead powerful dividends in the short run and in the long run.
When we do a DEXA scan at Valley Healthspan we discuss a number of metrics, including body fat percentage, visceral adipose tissue, and lean mass. The lean mass measurement by DEXA scan is a great marker of skeletal muscle mass, and in fact is the most commonly used surrogate for muscle mass in research studies. The appendicular lean mass index (ALMI) is the one we really emphasize, which is a measurement of the lean mass in the arms and legs (controlled for height), and we are able to determine your percentile based on age and sex. It’s always interesting to see the DEXA scan repeated after 6-12 months, as we are able to calculate how much your fat mass and lean mass has increased or decreased.
Your lean mass is a great metric to know and getting this test done on a regular basis provides valuable feedback on your lifestyle efforts!
VO2 Max
I wrote about the VO2 max fitness test in my blog VO2 Max and Longevity, and will summarize some of the key points here. It has become quite en vogue to know your VO2 max score. Among longevity enthusiasts VO2 max has reached a status on par with other well-known health metrics, including BMI and blood pressure. In fact, many experts argue that your VO2 max score more accurately predicts how long you will live than any other modifiable variable that we know, and that includes blood pressure, cholesterol, and presence of heart disease or diabetes.
What exactly is VO2 max? The VO2 max is a functional test of the combined working capacity of your lungs, heart, and muscles, and it’s considered the gold standard measure of a person’s fitness level. Specifically, it is a measurement of how much oxygen your body can utilize when undergoing strenuous exercise.
Although there are numerous indirect ways to estimate your VO2 max, the direct (and most accurate) measurement of VO2 max involves a dynamic test in which an individual exercises to maximal intensity while wearing a mask which measures how much oxygen they consume and carbon dioxide they expire. This can be done on an exercise machine such as a treadmill or stationary bike. After a sufficient warm-up time, the level of exercise intensity is slowly ramped higher until the volume of oxygen consumed reaches a plateau.
The VO2 max has become a popular metric for at least two reasons: 1) the magnitude by which it predicts longevity (and other chronic disorders such as cardiovascular disease and Alzheimer’s disease), and 2) the fact that it is highly modifiable.
A well-known study that demonstrates the power of VO2 max to predict longevity was published in JAMA Network Open in 2018. In this study researchers tested the VO2 max at baseline of 122,007 adults at an average age of 53 years old. They then divided the group into four quartiles based on their baseline VO2 max test: “Low”, “Below Average”, Above Average”, and “High”. As they followed these groups over time, the Low group had a mortality rate that was nearly 4 times higher than the High group. Furthermore, compared to the Above Average group, the Low group had a mortality rate that was 2.7 times higher, and 1.9 times higher compared to the Below Average group.
For comparison sake, the difference in mortality rates of other well known risk factors in this study were less impressive. For example, smokers had a mortality rate that was 1.4 times higher than that of nonsmokers, and those with a diagnosis of heart disease had a mortality rate that was 1.3 times higher than no heart disease. These risk factors are important for sure, but they pale compared to the incredible robustness of the impact of VO2 max on our health.
Other large studies have shown that an increase in VO2 max level of 1 MET (which is equivalent of 3.5 mL/kg/min) is associated with a 10% to 20% decrease in mortality rate. An increase in VO2 max level of 3.5 mL/kg/min is highly achievable through a dedicated training program, and in many cases your VO2 max can be increased much higher than this.
How do you improve your VO2 max? About 50% of your VO2 max score is innate (i.e. determined by your genetics), so there’s not much you can do about that. But the other 50% is determined by your level of physical activity and your exercise habits. VO2 max can be increased by at least 15-20% from baseline with a dedicated training program.
Any type of exercise can improve your VO2 max level, and this is especially true for those who are starting with a low fitness level at baseline. But research studies consistently show that high-intensity interval training (HIIT) leads to the biggest increases in VO2 max. HIIT programs generally involve repeated, short (3-8 minutes) intervals of near maximum intensity effort, followed by short periods of rest. A HIIT routine can be done with a wide variety of exercises, including running, biking, elliptical, and rowing.
A classic HIIT protocol, and one that has a considerable amount of research behind it, is the 4×4 protocol. After a 10-15 minute warm-up, the 4×4 protocol involves exercising for 4 minutes at a very high intensity (achieving a heart rate at least 90-95% of your maximum heart rate), then resting for 3-4 minutes, then repeating for 4 intervals. There are numerous other HIIT protocols that you can find with a quick internet search.
HIIT workouts are not easy. Many people find that working with a coach or a workout partner can provide the accountability and motivation necessary to stay consistent with the demanding requirements of a HIIT program. But when incorporated within the context of a well-rounded exercise regimen, high-intensity interval training has the potential to improve your lifespan and healthspan as much as any other intervention available.
Conclusion
Valley Healthspan’s Age Management package includes a before and after measurement of both lean mass by DEXA scan and VO2 max. Throughout the 6-month program you’ll work with nutrition and exercise experts to optimize your lifestyle, and you’ll work with Dr. Olson at Valley Healthspan to optimize your hormone health, metabolic health, and other longevity-focused treatments. Our goal is to provide a personalized and proactive approach to optimizing your quality of life, your physical and mental function, and your overall wellness as you age.
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