5th January 2020, Dr Chee L Khoo
Athletes and highly active people are not immune to coronary artery disease. There are some studies which suggest that despite the high levels of physical activity, these individuals have a higher prevalence of coronary artery calcification (CAC) compared with controls with low atherosclerotic risks (1,2). Is this increased level of CAC associated with increased mortality? Should these individuals continue to exercise at that high levels?
Current physical activity guidelines recommend at least 150 minutes of moderate intensity exercises or 75 minutes of high intensity exercises weekly (3). We know at that volume of exercise, cardiovascular mortality and all cause mortality is lower. Is more of a good thing better? The Copenhagen City Heart Study demonstrated that the dose-response curve between exercise and mortality is in the form of a U (or J) curve (4). Light and moderate joggers have lower mortality than sedentary non-joggers, whereas strenuous joggers have a mortality rate not statistically different from that of the sedentary group.
Thus, we have 2 issues to deal with here:
- Do individuals who are highly active have a higher prevalence of CAC?
- In these individuals, is the higher levels of CAC associated with increased mortality?
We may not have too many of these patients but when they present for advice as to whether it is safe for them to continue to exercise at that level, we need some clarity from the evidence that we have. There are not too many studies reporting on the mortality rates in highly active individuals with subclinical atherosclerosis. The Cooper Center Longitudinal Study (CCLS) is a prospective study initiated to evaluate the association between cardiorespiratory fitness (CRF), physical activity, and health (5). The results caught my eye as the study design answered the two questions very nicely.
The Cooper Clinic, Dallas, Texas, is a preventive medicine practice begun in 1970 that focuses on lifestyle modification for optimal health. Out of a base cohort of 28,880 men, 18564 aged between 40-80 years were selected after those who had pre-existing coronary or cerebral disease and those with incomplete data were excluded. Self-reported physical activity (“fitness”) were corroborated on treadmill exercise test. Maximal MET levels (1 MET = 3.5 mL/O2 × kg−1 × min−1) were estimated from the final treadmill speed and grade.
Following detailed review of the self-reported physical activity questionnaire with the patient, physical activity was categorised into:
- ≥3000 METS-min/week
- 1500-3000 METS-min/week
- <1500 METS-min/week
The guideline recommendation of >150 mins of moderate intensity exercise is almost equivalent to 500 METS-min/week. CAC was categorised as either <100 Agatston (AU) (low risk) or ≥100 AU (higher risk).
Men in the most highly active category (>3000 MET-min/wk) were slightly older, were less likely to smoke, had lower BMI and blood glucose and triglyceride levels and higher HDL levels. Most were not on a statin. The mean follow up was 10.4 years. The mean physical activity volume in the most highly active group was slightly more than 4600 MET-min/wk, which is equivalent to running ~10 km/day at a pace of about 6.5 minutes per km (hey that’s about my speed for long endurance running!).
Men at the highest physical activity level (>3000 METS-min/week) were 11.0% more likely to have CAC of at least 100 AU compared with men with lower physical activity levels.
Men with >3000 METS-min/week with CAC <100 AU
Compared with men with between 1500-3000 METS-min/week, men with the highest physical activity had a 50% reduction in all-cause mortality.
Men with >3000 METS-min/week with CAC >100 AU
Compared with men with between 1500-3000 METS-min/week, men with the highest physical activity had a tendency for lower all cause mortality although it did not reach statistic significance. In other word, it was not inferior (not worse).
At all levels of CAC, men who had the highest physical activity had a lower mortality than men with lower activity levels.
In summary, the CCLS suggests that “that high levels of physical activity (>3000 MET-min/wk) are associated with prevalent CAC but are not associated with increased all-cause or CVD mortality after a decade of follow-up, even in the presence of clinically significant CAC levels”.
Phew! I can continue to train for and run marathons for many more years to come. You too can reassure your patients of the same.
- Merghani A, Maestrini V, Rosmini S, et al. Prevalence of subclinical coronary artery disease in masters endurance athletes with a low atherosclerotic risk profile. Circulation. 2017;136(2):126-137. doi:10.1161/CIRCULATIONAHA.116.026964
- Aengevaeren VL, Mosterd A, Braber TL, et al. Relationship between lifelong exercise volume and coronary atherosclerosis in athletes. Circulation. 2017;136(2):138-148. doi:10.1161/CIRCULATIONAHA.
- 027834Leavitt MO. Physical Activity Guidelines for Americans. Washington, DC: Office of Disease Prevention and Health Promotion; 2008. https://health.gov/paguidelines/guidelines/intro.aspx.
- Schnohr P, O’Keefe JH, Marott JL, Lange P, Jensen GB. Dose of jogging and long-term mortality: the Copenhagen City Heart Study. J Am Coll Cardiol. 2015;
- DeFina L, Radford N, Barlow C, et al. Association of All-Cause and Cardiovascular Mortality With High Levels of Physical Activity and Concurrent Coronary Artery Calcification. JAMA Cardiol. 2019;4(2):174-181. doi:10.1001/jamacardio.2018.4628