PARIS – All lifestyle-related cardiovascular risk factors aren’t equal in power when it comes to secondary prevention after a first acute MI, according to a massive Swedish registry study.
Dr. Emil Hagstrom
Insufficient physical activity and current smoking were consistently the strongest risk factors for all-cause mortality, major adverse cardiovascular events, and other key adverse outcomes in an analysis from the SWEDEHEART registry. The study included 65,002 patients discharged after a first MI and 325,010 age- and sex-matched controls with no prior MI followed for a median of 5.5 years and maximum of 12, Emil Hagstrom, MD, PhD, reported at the annual congress of the European Society of Cardiology.
Strongest lifestyle risk factors
The study examined the long-term relative importance of control of six major lifestyle risk factors for secondary cardiovascular prevention: current smoking, insufficient physical activity, blood pressure of 140/90 mm Hg or more, obesity, a fasting blood glucose of at least 126 mg/dL, and an LDL cholesterol of 70 mg/dL or more. Notably, two risk factors that physicians often emphasize in working with their patients with known coronary heart disease – an elevated LDL cholesterol and obesity – barely moved the needle. Out of the six risk factors scrutinized, those two consistently showed the weakest association with long-term risk of adverse outcomes. Occupying the middle ground in terms of predictive strength were hypertension and elevated blood glucose, according to Dr. Hagstrom, a cardiologist at Uppsala (Sweden) University.
Risk factor status was assessed 6-10 weeks post MI. Insufficient physical activity was defined as not engaging in at least 30 minutes of moderate-intensity exercise on at least 5 days per week. And when Dr. Hagstrom recalculated the risk of adverse outcomes using an LDL cholesterol threshold of 55 mg/dL rather than using 70 mg/dL, as recommended in new ESC secondary prevention guidelines released during the congress, the study results remained unchanged.
Cumulative effects
A key SWEDEHEART finding underscoring the importance of lifestyle in secondary prevention was that a linear stepwise relationship existed between the number of risk factors at target levels and the risk of all of the various adverse outcomes assessed, including stroke and heart failure hospitalization as well as all-cause mortality, cardiovascular mortality, and major bleeding.
Moreover, patients with none of the six risk factors outside of target when assessed after their MI had the same risks of all-cause mortality, cardiovascular mortality, and stroke as the matched controls.
For example, in an analysis adjusted for comorbid cancer, chronic obstructive pulmonary disease, and dementia, post-MI patients with zero risk factors had the same long-term risk of cardiovascular mortality as controls without a history of MI at baseline. With one risk factor not at target, a patient had a 41% increased risk compared with controls, a statistically significant difference. With two out-of-whack risk factors, the risk climbed to 102%. With three, 185%. With four risk factors not at target, the all-cause mortality risk jumped to 291%. And patients with more than four of the six risk factors not at target had a 409% greater risk of all-cause mortality than controls who had never had a heart attack.
When Dr. Hagstrom stratified subjects by age at baseline – up to 55, 56-64, 65-70, and 70-75 years – he discovered that, regardless of age, patients with zero risk factors had the same risk of all-cause mortality and other adverse outcomes as controls. However, when risk factors were present, younger patients consistently had a higher risk of all adverse outcomes than older patients with the same number of risk factors. When asked for an explanation of this phenomenon, Dr. Hagstrom noted that younger patients with multiple risk factors have a longer time to be exposed to and accumulate risk.
Follow-up of the study cohort will continue for years to come, the cardiologist promised.
At an ESC congress highlights session that closed out the meeting, Eva Prescott, MD, put the SWEDEHEART study at the top of her list of important developments in preventive cardiology arising from the congress.
“This is an excellent national registry I think we’re all envious of,” commented Dr. Prescott, a cardiologist at Copenhagen University. “The conclusion of this registry-based data, I think, is that lifestyle really remains at the core of prevention of cardiovascular events still today.”
The SWEDEHEART study analysis was funded free of commercial support. Dr. Hagstrom reported serving as a consultant to or receiving speakers’ fees from Amgen, AstraZeneca, Bayer, Novo Nordisk, and Sanofi.