Paris, France - In the first study to ever assess the prognostic value of a change in heart rate (HR) over a number of years, French doctors have found that there is a relation between this variable and mortality [1]. Dr Xavier Jouven (Hôpital Européen Georges Pompidou, Paris, France) and colleagues report their findings in a study published online November 7, 2008 in the American Journal of Cardiology.

They found that in a cohort of healthy policemen, HR at rest and its change over five years were both predictors of death, independent of the standard cardiovascular risk factors. Those whose HR rose by more than three beats per minute (bpm) over this time period had an almost 20% increased mortality risk compared with men whose HR remained unchanged.

Jouven told heartwire that this is "an important paper and the second step" in a jigsaw. "We knew before that a person with a high heart rate has a high mortality. Now this article shows we are advancing in the research concerning the potential association between HR and mortality."

Change in HR over a five-year period conferred additional information beyond HR at rest and the usual risk factors.

Dr Franz Messerli (St Luke's-Roosevelt Hospital, New York) commented to heartwire: "The present study is unique in that it shows that patients whose heart rate increased during a five-year period had an . . . increased mortality risk. Of note, the policemen who did best were the ones who had a low heart rate at the beginning of the Paris Prospective Study 1 and whose heart rate remained unchanged."

The observational, although prospective, study followed 5139 asymptomatic men (aged 42 to 53 years) who were recruited from 1967 to 1972 and had their HRs measured at rest in standardized conditions every year for five consecutive years. HR change was defined as the difference between HR at examination 5 and HR at inclusion. Subjects were divided into the following tertiles: decrease >4 bpm; unchanged (from -4 to +3 bpm); or increase >3 bpm.

After adjustments were made for confounding factors, including baseline HR at rest, compared with subjects with unchanged HRs, those with decreased HRs during the five years had a 14% decreased mortality risk (RR 0.86, 95% CI 0.74-1.00; p=0.05), whereas men with increased HRs during the five years had a 19% increased mortality risk (RR 1.19, 95% CI 1.04-1.37; p<0.012).

Because the study was performed in relatively young French policemen, the generalizability of the findings to women or a more unselected or recent population cohort is unclear, the researchers point out.

They say that the association between high HR at rest and mortality is consistent with data already published in a number of epidemiologic studies and that high HR at rest could reflect underlying abnormalities, possibly via increased mechanical stress on the arterial wall and heart.

"We found that change in HR over a five-year period conferred additional information beyond HR at rest and the usual risk factors [and] was an independent predictor of mortality in middle-aged men," they observe.

Messerli told heartwire that "the most common reason for a slow heart rate in young to middle-aged subjects, such as in the present study, is regular conditioning. Conceivably, therefore, subjects in this group were the ones who exercised regularly and continued to exercise regularly throughout the five-year period, thereby keeping heart rate slow. As expected, [body-mass index] BMI was lowest in this group.

"It is of little surprise, then, that these slow-heart-rate policemen had a drastically lower mortality than those who started out with an increased heart rate [that] accelerated . . . even more during the five-year period," he added.

Jouven told heartwire that the next step to prove an association will be with some kind of interventional trial aimed at investigating whether an induced HR decrease—with, for example regular exercise—is associated with a decrease in mortality risk. "If we change HR, do we change mortality?" he wondered.