Change in cardiorespiratory fitness over time linked with CV event risk

Issue: November 2016

BOCA RATON, Fla. — An interval change in cardiorespiratory fitness is independently and inversely associated with risk for incident atrial fibrillation/flutter, stroke and mortality, according to research presented at the American Society for Preventive Cardiology’s Congress on Atherosclerotic Cardiovascular Disease Prevention.

Nasir Hussain, MD , of Mayo Clinic, Rochester, Minnesota, and colleagues conducted a study to examine long-term effects of change in cardiorespiratory fitness on the incidence of AF/flutter, stroke and all-cause mortality. Previous data have highlighted an inverse association between cardiorespiratory fitness and incident AF, stroke and mortality and, recently, other studies have shown that an interval change in cardiorespiratory fitness has long-term effects on mortality. However, research is lacking on the effect of interval change in cardiorespiratory fitness on risk for AF/flutter and stroke, Hussain said during a presentation.

For this study, functional aerobic capacity was used as an estimate for cardiorespiratory fitness. This is in contrast to other research in this area that has utilized self-reported physical activity as a surrogate to estimate metabolic equivalents (METs), Hussain said.

The researchers analyzed a cohort of 76,000 participants who underwent exercise stress tests at Mayo Clinic in Rochester from 1993 to 2010. The analysis was limited to the population living in Olmsted County and other neighboring countries in Minnesota (n = 14,095) and only those with at least two treadmill exercise stress tests, for a final cohort of 3,096 participants. Participants with prior AF/flutter or stroke and those aged younger than 18 years were excluded. One-quarter of the cohort was female and 93% were white.

During a median follow-up of 13 years, 15.5% of participants died, 13% developed AF/flutter and 11.9% developed stroke.

The cohort was divided into three groups based on gains, losses or stability of functional aerobic capacity during follow-up. Among participants with incident AF/flutter, 13.9% exhibited a loss in cardiorespiratory fitness, 10% exhibited stable cardiorespiratory fitness and 15.8% exhibited gains in cardiorespiratory fitness. Among participants with stroke, 14.1% exhibited a loss in cardiorespiratory fitness, 8.4% exhibited stable cardiorespiratory fitness and 13.2% exhibited gains in cardiorespiratory fitness. Among participants who died, 18.7% exhibited a loss in cardiorespiratory fitness, 11.1% exhibited stable cardiorespiratory fitness and 16.9% exhibited gains in cardiorespiratory fitness, according to the data presented.

A 10% higher functional aerobic capacity at baseline was associated with 8% lower risk for AF/flutter, 10% lower risk for stroke and 17% lower risk for mortality. An interval increase of 10% in functional aerobic capacity resulted in risk reduction by 12% for AF/flutter, 11% for stroke and 18% for mortality, Hussain said.

After multivariate adjustment, participants who exhibited gains in cardiorespiratory fitness had a 26% risk reduction for AF/flutter, 39% risk reduction for stroke and 52% risk reduction for mortality, he said.

In addition, participants were divided into two groups for each exercise stress test and were classified as fit (functional aerobic capacity 90%) or unfit (functional aerobic capacity < 90%). The researchers found that participants who changed their fitness category on a repeat exercise test had a significant change in the risk for incident AF/flutter. Unfit participants who were considered fit on the repeat test had a 44% risk reduction for AF/flutter (HR = 0.66; 95% CI, 0.48-0.91), 12% risk reduction for stroke (HR – 0.88; 95% CI, 0.61-1.21) and 46% risk reduction for all-cause mortality (HR = 0.55; 95% CI, 0.41-0.74). Fit participants who were considered unfit on the repeat test had a 43% increased risk for incident AF/flutter (HR = 1.43; 95% CI, 1.02-2.02), 44% increased risk for stroke (HR = 1.44; 95% CI, 1.02-2.02) and 51% increased risk for all-cause mortality (HR = 1.1-1.12).

“Our study confirms the previously described inverse association of cardiorespiratory fitness with AF/flutter, stroke and mortality ... [and] confirms the long-term effects of an interval change in cardiorespiratory fitness on mortality and outcome. We have, for the first time, shown that an interval change in cardiorespiratory fitness also independently and inversely associates with the risk of incident AF/flutter and stroke,” Hussain said. “

Reference:

Hussain N, et al. Abstract 105. Presented at: American Society for Preventive Cardiology Congress on Atherosclerotic Cardiovascular Disease Prevention; Sept. 16-18, 2016; Boca Raton, Fla.

Disclosure: Hussain reports no relevant financial disclosures.