BMI and exercise influence heart failure subtypes differently, the new study shows.
When the heart is no longer able to pump enough blood to meet the body's oxygen demands, it is referred to as heart failure - a chronic and progressive condition.
An estimated 5.7 million adults in the United States have heart failure. In fact, heart failure was responsible for 1 in 9 deaths in the U.S. in 2009.
There are a number of subtypes of heart failure, one of which is called heart failure with preserved ejection fraction (HFpEF). This form of the condition is characterized by a stiffening of the left ventricle and a reduction in its ability to relax between contractions.
The stiffening associated with HFpEF means that the ventricle is unable to fill with an adequate amount of blood, and it therefore pumps less oxygen-rich blood around the body.
Lifestyle factors are known to increase the risk of heart failure, including lower levels of physical activity and a higher BMI. Because HFpEF accounts for roughly half of all heart failure cases and typically responds less well to current therapies, there is an important emphasis on prevention.
A new study, carried out at the University of Texas Southwestern Medical Center in Dallas, aimed to investigate the influence of common risk factors on HFpEF, specifically. Their results are published this week in the Journal of the American College of Cardiology.
The investigators - led by Dr. Jarett D. Berry, associate professor in the department of internal medicine and clinical sciences - used data from 51,541 participants. This information was taken from three studies: the Women's Health Initiative, the Multiethnic Study of Atherosclerosis, and the Cardiovascular Health Study.
All participants were free of cardiovascular disease at the start of the study and were assessed for levels of physical activity and BMI. Across the cohort, over the following years, there were 3,180 heart failure events, as confirmed by independent medical experts.
The data showed that participants with higher levels of physical activity were most often male, white, and likely to have had higher income and education levels. They were also less likely to smoke, have diabetes, obesity, and hypertension.
Conversely, participants with higher BMIs tended to be younger, exercise less, and have a higher prevalence of cardiovascular risk factors.
"We consistently found an association between physical activity, BMI, and overall heart failure risk. This was not unexpected; however, the impact of these lifestyle factors on heart failure subtypes was quite different."
Dr. Jarett D. Berry
Of the 3,180 heart failure events, 39.4 percent were HFpEF, 28.7 percent were heart failure with reduced ejection fraction (HFrEF) - a subtype associated with a weaker heart muscle that cannot pump adequately - and 31.9 percent were unclassified.
Compared with individuals who did no physical activity, the researchers found a reduction in heart failure risk that matched the exercise level:
- Low physical activity: 6 percent reduction in risk
- Participants who met recommended levels of physical activity: 11 percent reduction in risk
- Participants who exceeded recommended levels of physical activity: 22 percent reduction in risk.
HFpEF vs. HFrEF
When the data were further split into HFpEF and HFrEF, differences in the effect of exercise on heart failure risk were uncovered. Individuals who exceeded recommended levels of activity had a 19 percent reduced risk of HFpEF, compared with those who did not exercise. However, there was no such association between elevated physical activity and risk of HFrEF.
Higher BMIs were, unsurprisingly, associated with a higher overall heart failure risk. However, the relationship between BMI and heart failure subtypes was similar to that of exercise. BMI had a more significant impact on the risk of HFpEF than HFrEF.
The findings hammer home the importance of BMI and physical activity in preventing HFpEF. First author, Dr. Ambarish Pandey, a cardiology fellow at the University of Texas Southwestern Medical Center, said:
"There was a distinct relationship between both physical activity and BMI and the different heart failure subtypes, which may have important clinical and public health implications. These data suggest the importance of modifying lifestyle patterns to help prevent HFpEF in the general population."
Although the study was observational and, therefore, cannot prove cause and effect, it will certainly spur further investigation.