Dr. Kyle Mandsager and colleagues at the Cleveland Clinic reported on the long term mortality ( median followup of 8.4 years) on 122,007 patients who were referred for symptom limited exercise treadmill testing.They were stratified by age and sex into five cardiorespiratory performance groups .(low,below average,above average,high and elite expressed as metabolic equivalent units (METs) which is 3.5 ml 02 uptake/kilogram/minute) which was estimated by treadmill incline and speed.
The 25th, 50th,75th and 97.7 percentiles were tabulated for age and sex .Low is defined as less than 25 th percentile and elite as greater than 97.7 th percentile.
They found that cardiorespiratory fitness (CRF) was "inversely associated with long term mortality with no observed upper limit of benefit. Cardiorespiratory fitness is a modifiable indicator of long term mortality …"
We have another coarse grain study that could be used to support the thesis that exercise is good and lots of exercise is better and you will live longer. I don't believe it is that simple.
This study does not correlate exercise history with longevity rather it correlates exercise performance with longevity. Admittedly exercise performance or capability does correlate with exercise history but they are not exactly the same thing. Further, while it may well be the case that CRF is modifiable and that one can actually improve mortality by improving one's CRF their data does not direct address those point although I like to believe that proposition is true.
What is shown impressively in their Figure 1, is the 10 year survival probability for the above average or the high group is about 95% ( just by my eyeballing the chart) versus the low group where the survival probability is slightly less than 80%
So how low is the low group in terms of exercise capability.For example in the 70-79 year age group
What about a 40 year old? Subjects in the 40-49 year old group had a MET levels of less than 9.8. This corresponds to being able to finish Stage 2 and a bit into Stage 3 and be able to run a 12 minute mile.
Someone in the high category would have a MET value of 12.5 to 14.6 which corresponds to being able to reach Stage 5 on the Bruce protocol and run a mile in 9 minutes.
The authors made comments that are headline attractors. "The increase in all cause mortality associated with reduced CFR (low versus elite:adjusted HR,5.04:95% CI, 4.10--6.20;p<.002) was comparable to or greater than traditional risk factors." See figure 2 in their artcle for details of that comparison.<0 .001...was="" 2="" comparable="" compared="" diabetes="" esrd.="" factors.="" factors="" figure="" greater="" hypertension="" nbsp="" or="" p="" risk="" see="" smoking="" than="" the="" their="" to="" traditional="">
Skeptics of the thesis that there is a "U -shaped"curve relating risk of death to exercise level will perhaps find some comfort in their finding : "There was also no evidence to suggest relative harm associated with extreme levels of fitness in these subgroups of patients"In fairness I should add that no one has claimed that excessive fitness is deleterious but rather the claim has been that excessive exercise may be harmful, again realizing that fitness levels and exercise levels are highly correlated.
I don't think anyone has claimed that being too fit is harmful to health or lowers longevity.
Nitpicking aside, their data provide more fuel to the argument that exercise ( or at least CRF) is good and apparently the more the better.
1)Mandsager,k et al "Association of cardiorespiraory fitness with long-term mortality among adults undergoing exercise treadmill testing" JAMA Network open, 2018 1 (6)Oct 19
.
No comments:
Post a Comment