White men who exercise at high levels are 86% more likely than people who exercise at low levels to experience coronary artery calcification by middle age, a confounding US cohort study suggests.
The study looked at the physical activity trajectories of 3,175 black and white participants in the multicentre, community-based, longitudinal cohort CARDIA study, and assessed the presence of coronary artery calcification (CAC), among participants.
CAC is a clinical measure of the accumulation of calcium and plaque in the arteries of the heart. The presence and amount of CAC, is a significant warning sign to doctors that a patient may be at risk for developing heart disease and a signal to consider early preventive care.
Heart disease is the leading cause of death for both men and women in the US.
The study group consisted of CARDIA participants who self-reported physical activity during at least three of eight follow-up examinations over 25 years, from 1985 through 2011. At baseline, participants were ages 18 to 30 living in Birmingham, Alabama; Chicago; Minneapolis; and Oakland, California.
Researchers categorised participants into three distinct trajectory groups, based on physical activity patterns: trajectory group one was defined as exercising below the national guidelines (less than 150 minutes a week), group two as meeting the national guidelines for exercise (150 minutes a week), and group three was defined as exercising three-times above the national guidelines (more than 450 minutes a week).
"We expected to see that higher levels of physical activity over time would be associated with lower levels of CAC," said Deepika Laddu, assistant professor of physical therapy in the UIC College of Applied Health Sciences. Instead, Laddu and her colleagues found that participants in trajectory group three, or those who exercised the most, were 27% more likely than those in trajectory group one to develop CAC by middle age. CAC was measured during the participants' 25th year in the study using computed tomography, a CT scan, of the chest. At year 25, participants were ages 43 to 55.
When these findings were stratified by race and gender, they found that white men were at the highest risk-they were 86% more likely to have CAC. There was no higher odds of CAC for black participants who exercised at this level, and while there was a similar trend for white women it was not statistically significant.
According to Laddu and study co-author Dr. Jamal Rana, similar population-based cohort studies on cumulate exercise dose have caused some controversy by showing U-shaped trends of association between physical activity and disease risk. "So we performed this study to see if we can solve part of this puzzle," said Rana, a cardiologist at Kaiser Permanente in Oakland.
Unique to the new study is the evaluation of long-term exercise patterns, from young adulthood into middle age. "Because the study results show a significantly different level of risk between black and white participants based on long-term exercise trajectories, the data provides rationale for further investigation, especially by race, into the other biological mechanisms for CAC risk in people with very high levels of physical activity," said Laddu.
"High levels of exercise over time may cause stress on the arteries leading to higher CAC," said Rana, "however this plaque build-up may well be of the more stable kind, and thus less likely to rupture and causes heart attack, which was not evaluated in this study." Rana says they plan to evaluate for outcomes, such as heart attacks and death, next.
While the study suggests that white men who exercise at high levels may have a higher burden of CAC, "it does not suggest that anyone should stop exercising," Laddu said.
Objective: To evaluate 25-year physical activity (PA) trajectories from young to middle age and assess associations with the prevalence of coronary artery calcification (CAC).
Patients and Methods: This study includes 3175 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study who self-reported PA by questionnaire at 8 follow-up examinations over 25 years (from March 1985-June 1986 through June 2010-May 2011). The presence of CAC (CAC>0) at year 25 was measured using computed tomography. Group-based trajectory modeling was used to identify PA trajectories with increasing age.
Results: We identified 3 distinct PA trajectories: trajectory 1, below PA guidelines (n=1813; 57.1%); trajectory 2, meeting PA guidelines (n=1094; 34.5%); and trajectory 3, 3 times PA guidelines (n=268; 8.4%). Trajectory 3 participants had higher adjusted odds of CAC>0 (adjusted odds ratio [OR], 1.27; 95% CI, 0.95-1.70) vs those in trajectory 1. Stratification by race showed that white participants who engaged in PA 3 times the guidelines had higher odds of developing CAC>0 (OR, 1.80; 95% CI, 1.21-2.67). Further stratification by sex showed higher odds for white males (OR, 1.86; 95% CI, 1.16-2.98), and similar but nonsignificant trends were noted for white females (OR, 1.71; 95% CI, 0.79-3.71). However, no such higher odds of CAC>0 for trajectory 3 were observed for black participants.
Conclusion: White individuals who participated in 3 times the recommended PA guidelines over 25 years had higher odds of developing coronary subclinical atherosclerosis by middle age. These findings warrant further exploration, especially by race, into possible biological mechanisms for CAC risk at very high levels of PA.
Deepika R Laddu, Jamal S Rana, Rosenda Murillo, Michael E Sorel, Charles P Quesenberry, Norrina B Allen, Kelley P Gabriel, Mercedes R Carnethon, Kiang Liu, Jared P Reis, Donald Lloyd-Jones, J Jeffrey Carr, Stephen Sidney
[link url="https://www.sciencedaily.com/releases/2017/10/171016144846.htm"]University of Illinois at Chicago material[/link]
[link url="http://www.mayoclinicproceedings.org/article/S0025-6196(17)30577-3/fulltext"]Mayo Clinic Proceedings abstract[/link]