Physical activity may paradoxically hasten build-up of heart attack risk factor
Physical activity may paradoxically accelerate the accumulation of calcium deposits (plaque) in the coronary arteries, the quantity of which is used to predict future risk of cardiovascular disease, according to study published online in the journal Heart.
However, the researchers emphasise that the findings do not negate the various health benefits of exercise.
The coronary artery calcium score, abbreviated CAC, is used to guide treatment aimed at preventing a heart attack or stroke. Statins are recommended for the majority of persons with a CAC score of 100 or greater.
Regular physical activity has been shown to reduce the risk of obesity, diabetes, heart attack/stroke, and death in a dose-dependent manner.
Despite these significant health benefits, research indicates that persons who are extremely physically active appear to have high levels of calcium deposits in their coronary arteries. As a result, it is unclear if exercise is connected with calcification (artery hardening).
To further investigate this, the researchers examined healthy adults who received routine comprehensive examinations at two major health centres in Seoul and Suwon, South Korea, between March 2011 and December 2017 as part of the Kangbuk Samsung Health Study.
Participants completed a questionnaire at each health check, which included questions on their medical and family history, lifestyle, and educational level. Additionally, body mass index (BMI), blood pressure, and blood fats were measured.
At the initial check-up, physical activity was classified formally as inactive, moderately active, or 'health-enhancing' (intense) physical activity using a validated questionnaire.
Over an average of three years, scans were used to monitor the development and/or progression of coronary artery calcification, which was subsequently graded (CAC score).
The final analysis included 25,485 people (22,741 men and 2744 women) who were at least 30 years old and had at least two CAC scores.
Around 47% (11,920), 38% (9683), and 15% (3882) of them were sedentary, moderately active, or severely active—equivalent to running 6.5 kilometres each day.
Participants who were more physically active tended to be older and less likely to smoke than participants who were less physically active. Additionally, they had lower total cholesterol, greater hypertension, and existing calcium deposits in their coronary arteries.
Over time, regardless of CAC scores at the start of the monitoring period, a graded connection between physical activity level and the occurrence and advancement of coronary artery calcification emerged.
At the commencement of the monitoring period, the estimated adjusted average CAC scores for all three groups were 9.45, 10.20, and 12.04, respectively.
However, increased physical activity was related with a faster development of CAC scores in both those with and without calcium deposits at the start of the monitoring period.
Even after accounting for potentially important characteristics such as BMI, blood pressure, and blood lipids, the estimated adjusted 5-year average increases in CAC scores in moderately and extremely active participants were 3.20 and 8.16, respectively, compared to those who were sedentary.
As this is an observational study, it cannot show causation. Additionally, the researchers acknowledge many study limitations, including the absence of objective measures of physical activity and data on incident heart attacks/strokes, as well as CAC density and volume.
They explain that physical exercise may exacerbate coronary atherosclerosis (artery narrowing) by mechanical stress and arterial wall injury, as well as the physiological responses it induces, such as increased blood pressure and parathyroid hormone. Physical exercise, they argue, may also alter the influence of nutrition, vitamins, and minerals.
“Another option is that physical activity may improve CAC scores without raising the risk of [cardiovascular disease],” they write.
“The cardiovascular advantages of physical activity are undeniable,” they emphasise, citing national standards that encourage at least 150–300 minutes of moderate intensity aerobic physical activity or 75–150 minutes of vigorous intensity aerobic physical activity each week.
“However, patients and clinicians should bear in mind that physical activity may hasten the advancement of coronary calcium, possibly as a result of plaque repair, stability, and calcification,” they conclude.
Drs Gaurav Gulsin and Alastair James Moss of the University of Leicester's Department of Cardiovascular Science suggest in a related editorial, "Do these findings mean that we should discontinue using coronary artery calcium scores to assess coronary artery disease?"The study emphasises the difficulty of interpreting CAC values in people who have increased their physical activity or begun taking statins – both of which are associated with higher scores.
“While proponents suggest that it is a helpful tool for screening asymptomatic persons for subclinical atherosclerosis, clinicians should exercise caution in overusing this test in otherwise healthy individuals,” they caution.
Dr Moss adds in a related podcast that non-calcified plaque, which is more unstable and prone to rupture, may be more significant and should be scored to determine an individual's future risk of heart attack or stroke.
“Perhaps the target we should pursue is non-calcified plaque rather than calcified plaque,” he speculates. This was not seen in the study's scans.“Increasing rates of coronary artery calcification have been found in response to both statin medication and exercise. However, serial imaging with calcium scans is not always the ideal method for accurately assessing [cardiovascular disease] risk in these individuals.
However, he reiterates: "Clearly, exercise is one of the most effective approaches to attempt to manage cardiovascular risk among [symptomless individuals]."