First Look at Effects of Resting Heart Rate and Exercise on Heart-Disease Deaths

From Heartwire

Lisa Nainggolan

January 12, 2010 (Trondheim, Norway) — A high resting heart rate (HR) is associated with a higher risk of death from ischemic heart disease (IHD), particularly in younger women, new research shows [1]. While women were able to temper this adverse effect to some extent by exercising, the same did not seem to be true in men, the researchers report.

The risk of dying from IHD rose 18% for every 10-beats-per-minute (bpm) increase in resting HR in women up to the age of 70, report Dr Javaid Nauman (Norwegian University of Science and Technology, Trondheim, Norway) and colleagues in a study published online January 11, 2010 in the Journal of Epidemiology & Community Health. In men, there was around a 10% higher risk of IHD mortality for every 10 bpm increase in resting HR, regardless of age.

This is the first study to account for the combined effect of resting heart rate and physical activity on deaths from ischemic heart disease in a population that was reported to be free from cardiovascular disease at baseline, say Nauman et al.

Nauman told heartwire that in apparently healthy individuals, "clinicians are reluctant to prescribe heart-rate–lowering drugs," so an important message from this study is that there are nonpharmacological means to modulate heart rate. "By engaging in physical activity of moderate or high intensity, you can keep your heart rate in check and get the benefits. Do some workout and you will get the reward."

Men in Highest Quintile of Resting HR 73% More Likely to Die From IHD

In their prospective cohort study, the researchers enrolled and followed 25 000 men and 25 000 women from a county in Norway who were free from cardiovascular disease at baseline, from 1984 to 1986, in the HUNT study.

Information was collected on general health and lifestyle, including the frequency and intensity of exercise performed in a week, with five response options: 0, <1, 1, 2–3, and >4 times. Those who reported exercising at least once a week were also asked about the average duration (<15, 15–30, 30–60, >60 minutes) and intensity (light, moderate, or vigorous) of exercise. To assess the effect of total exercise volume, a summary score was constructed combining information on frequency, duration, and intensity.

During a mean of 18.2 years of follow-up, 2566 men and 1814 women died from cardiovascular causes. Resting HR was positively associated with the risk of cardiovascular disease, in particular IHD, in men, showing a gradual increase in mortality with increasing HR.

In men whose HR was 101 bpm or more (the highest quintile), the adjusted hazard ratio for IHD mortality was 1.73 compared with those in the reference group, whose resting HR was considered to be in the "normal" range of 61 to 72 bpm.

Among men, this association did not substantially differ by age. For each increment of 10 resting heart beats per minute among men, there was a 10% higher risk of death from IHD in those under 70 (p=0.004) and an 11% higher risk of death in the older age group (p=0.01).

Effects in Women Appear Age-Dependent

In women, the adjusted hazard ratio was 1.42 for IHD mortality in the highest quintile of women compared with those in the reference group.

In contrast to the men, the effects of resting HR were strongly dependent on age in women. Younger women (under 70) in the highest quintile for resting HR were twice as likely to die from IHD as those in the reference group (adjusted hazard ratio 2.11). But in those aged 70 and over, the corresponding hazard ratio was 0.95.

For each increment of 10 resting heart beats per minute, the risk of death from IHD was 18% higher in women less than 70 (p<0.001); no such association was observed among women 70 years and older.

"This effect could be caused by deaths at a relatively young age in women who were particularly vulnerable to a high resting HR," the researchers speculate.

"The present results contribute to extend the literature on the epidemiology of cardiovascular disease among women, as previously, data among women have been sparse, except for one large cohort study of postmenopausal women that showed that resting HR is an independent predictor of coronary events," say Nauman et al.

Physical Activity Protective, Particularly in Women

People who reported no physical activity were at consistently higher risk of CVD than those who reported any level of physical activity.

The findings with regard to exercise in women suggest that by being physically active, women with a high resting heart rate could avoid cardiovascular complications, say the Norwegian doctors.

Why exercise did not seem to attenuate the association of high resting HR with deaths from IHD among men remains unclear, they add, although it could be that men, "more so than women, tend to overestimate their levels of physical activity, and this in turn could have influenced the results.

"Future studies are warranted to investigate the association of resting HR and physical activity to assess the combination of intensity and volumes to have an optimal influence on IHD mortality," they conclude.

http://www.medscape.com/viewarticle/714974?sssdmh=dm1.580257&src=nldne&uac=71630FV