"Low levels of physical capability in middle age may signal poorer chances of survival over the next 13 years, according to a cohort study of 1355 men and 1411 women in the United Kingdom."
How was physical fitness (capability) measured?
"Nurses assessed grip strength, chair rise speed, and standing balance time of participants at age 53 years."
The physical tests were given at at age 53, and then the subjects were followed over the next 13 years (until age 66); any deaths among the group were recorded. The results were quite striking:
"During the follow-up period (13 years), there were 177 deaths (88 from cancer, 47 from cardiovascular disease, and 42 from other causes). The fully adjusted hazard ratio of all-cause mortality for participants in the lowest vs highest quintiles of physical capability was 3.68. Those who could not complete any of the 3 tests had death rates more than 12 times higher than those who were able to complete the tests."
177 out of the 2766 participants (6.4%) died over the 13 year period. To emphasize, the bottom 20% performers on the physical tests had a mortality rate 3.68 times that of the top 20%. More strikingly, those who could not complete any of the three tests died at a rate 12 times larger than those would could complete the tests. This is no small effect.
The authors interpreted their results in the following manner:
"Subpar performance on the tests in middle age likely reflects subclinical disease and aging processes rather than manifest diseases, making this population an important one for interventions, said the investigators."
In other words, a person who could not complete the tests may not show any clinical symptoms of a disease (i.e. subclinical) and yet be 10 times more likely to die than a person who completes the tests. Thus the tests could possess general diagnostic value identifying patients who may require greater attention because they either have an early subclincal stage of the disease, or they are more likely to acquire the disease in the not too distant future. The two main causes of death were cancer and heart disease (not surprisingly).
So what were these magical tests that could predict mortality?
1. Grip strength "was measured isometrically with an electronic handgrip dynamometer." The average grip strength was about 50kg for men and 30 kg for women.
2. Chair rise time (see Video 1) "was measured with a stopwatch as the time taken to rise from a sitting to a standing position with straight back and legs and then to sit down again 10 complete times as fast as possible." The average time for the 10 chair rises was ~20 seconds for both men and women.
3. Standing balance time "was measured, using a stopwatch, as the longest time, up to a maximum of 30 seconds, participants could maintain a one-legged stance in a standard position with their
eyes closed." The average standing balance time was 4-5 seconds for both men and women.
It is important to note that the above hazard ratios were not adjusted for confounding factors like body size and lifestyle factors. As you may imagine there was some correlation between physical performance and a trait like obesity:
"Participants with lower physical capability scores tended to have lower socioeconomic position; less healthy lifestyles; and higher prevalence of self-reported cardiovascular disease, diabetes, and severe respiratory symptoms when compared with those with higher scores."
However, even when adjusted for these confounding factors, the above association between low physical capability and higher mortality was still present although at a reduced significance.
I am curious whether these tests (or similar tests) could predict mortality for those older (or younger) than 53, and how they could be improved or supplemented by additional physical tests to make even better predictors. In the meantime you can test your chair rise time (Video 1).
Figure 1. Video for performing the chair rise time test.
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