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Thursday, September 06, 2018

Is the minimal level of recommended exercise sufficient to decrease the risk of heart failure?

In January 2017, I posted a blog commentary entitled " The minimum exercise levels of  the 2008 guidelines won't prevent heart failure". See here.

The gist of that commentary   was that the adherence to the minimal exercise levels indicated by the guidelines had been demonstrated by ample epidemiologic studies to reduce the incidence of cardiovascular disease (CVD) but  exercise at that level had not been demonstrated to reduce   heart failure (HF) incidence and that a higher amount of exercise was needed.

Since then I have more carefully studied a 2015 epidemiologic paper  by Pandy,which I had read before but obviously not with adequate attention , and a detailed physiologic comparison of cardiac function by Bella et al  in 4 groups of healthy subjects who varied  in their long term exercise levels to which I also had not paid appropriate attention. 

These considerations   resulted in a major revision my 2017 headline to " Adherence to the 2008 guideline will reduce HF incidence but more exercise will reduce HF risk significantly more"

Note: I have added an addendum to the 2017 posting  stating the headline is simply wrong 

So now to try and clean up the earlier erroneous  commentary .

First a review of some background:

The 2008 US and WHO guidelines recommend a minimum of 150 minutes of moderate exercise per week or 75 minutes of vigorous exercise. This corresponds to 500 MET minutes  per week or 8.3 MET hours .The US panel also said that further gain could be made by increasing that level to twice that amount. Moderate intensity was defined as requiring between 3 and 5.9 METS and vigorous greater than 6 METS.Note-the panel was addressing the risk of cardiovascular disease in general and not heart failure risk per se .

There is universal agreement that aerobic exercise will decrease heart disease risk ( and according to some studies-dementia,some cancers and type 2 diabetes) but there is disagreement as regards how little exercise  might be  sufficient to reduce cardiovascular risk  and how much exercise might be harmful. I leave those 2  questions  to another time.

In regard to HF:

Patel et (1) published a 2013 review of 5503 subjects age 65 and older from the Cardiovascular Health Study .They divided participants into inactive ,low level exercise ( 1-499 METS),Medium (500 to 999 METS )and high was defined as  greater than 1000 METS 

The hazard ratio (HR) for the low group was a non-statistically significant 0.87 (0.71-1.06,p=0.170.
The medium groups HR 0.68 (0.54-0.85)p=0.001
The high group HR 0.60(0.49-0.74, p=0.026<0 .001.="" p="">

Note that  the low and medium groups overlap the 500 level so  no conclusive verdict regarding HF risk reduction with 500 MET level can be made. You can say that the lowest exercise group enjoyed no reduction in HF risk but we do not know how many subjects were closer to the 1 than to the 500 level. We can say that the medium and high level  did demonstrate a HF  risk reduction but can conclude  nothing about the value of exercising at the 500 MET min level,which is the minimal level recommended by the 2008 panel. 

However, from Pandy's 2015 meta-analysis (2) that there demonstrable risk reduction  in HF in a group of subjects exercising at the 500 MET level. The authors examined data that included over 20 thousand HF events among 370 thousand participants in some 12 prospective cohort studies. 

The 500 MET-min  per week group had a reduction in HF risk ( HR-0.9 (0.81-0.92). However, a greater risk reduction was found in the 1000 MET Min per week group ) HR-.81 (0.77-0.86) and even greater reduction 0.65 (0.58 -0.73 ) in the group at the 2000MET min per week which corresponds to 10 hours of moderate exercise per week or 4 times the minimal amount suggested by the 2008 guidelines.

So the epidemiology  data indicate  that the lower level of recommended exercise will cause a measurable decrease in HF risk but in that regard more does seem to be better.Now to consider Bella's (3) physiological data which is consistent with Pandy's analysis.

 The following  2 paragraphs are copied from my earlier blog commentary.

" Dr Paul Bhella and his  associates  did extensive physiological studies on four groups of healthy volunteers over the age of 64. Four groups were designated   on the basis of their exercise history for the preceding 25 years. (not a typo) 1) sedentary-no more than one exercise session per week  2) casual exerciser-2-3 session per week 3) "committed" exercisers-4-5 session per week and 4)competitive master level athletes -6-7 session per week and competed regularly.  All had normal systolic function ( as defined by a normal resting ejection fraction) but groups one and two has decreased left ventricular compliance while the committed and competitive groups had left ventricular pressure volume curves and left ventricular masses similar to young healthy controls. ( see here for my  further comments and a few caveats regarding this paper including reference to Tanaka's work that challenges the notion that long term endurance exercise  does in fact preserve  ventricular compliance)

Quoting Bhella ". . at least 30 minutes of dynamic exercise per session for 4-5 days per week over a lifetime can  sufficiently prevent most of the decreases in LV compliance and distensibility observed with sedentary aging"

It appears that training at triathlon or marathon levels is not necessary to decrease long term risk of heart failure but the exercise has to be persistent. The term "lifelong "used by Bella may be an exaggeration but his subjects had a 25 year history of regular aerobic exercise.

Bella's data seems to confirm the notion that the 2/12 hours per week recommendation just might decrease the risk of HF with the caveat " if done over a long period of time". The same  group has subsequently published data showing that beginning a  more intense exercise program in a person's 60s or 70's will not result in improved left ventricular compliance but , of course, one would expect  health benefits.

I quote a key paragraph from Bella:

"This study's key finding is the novel observation that at least 30 minutes of dynamic exercise per session 4  to 5 days per week over a lifetime can sufficiently prevent most of the decrease in compliance and distensibility observed  with sedentary aging.This finding holds important implications for global health as ventricular stiffening has been implicated in the pathophysiology of many common CV conditions affecting the elderly.

Contrary to my earlier commentary the minimal levels of exercise may well be enough to decrease the risk of HF but exercise at about twice that levels is likely to bring about a more significant reduction. Note that Bella's comment of 30 minutes 4-5 days a week corresponds to the minimal recommendation of 150 minutes of moderate exercise per week.

1)Patel,K et al Prevention of heart failure in older adults may require higher levels of  physical activity than needed for other cardiovascular events.Int j Cardiol 2013 1905,-1909.

2)Pandy, A Dose Response relationship  between physical activity and risk of heart failure.A meta-analysis. Circulation 2015 132 1786-1794

3)Behlla,P Impact of lifelong exercise "dose"on left ventricular compliance and distensibility. JACC 64 1257-1267 2014  

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