Low Resting Heart Rate Linked to Violent Crime

Fran Lowry

September 09, 2015

Individuals who have a low resting heart rate are more prone to become violent criminals, victims of crime, and even have more accidents as adults compared with those who have normal resting heart rates, new research suggests.

In a study of more than 700,000 Swedish men, low resting heart rate in late adolescence was associated with an increased risk for violent criminality, nonviolent criminality, exposure to assault, and unintentional injury in adulthood.

The study, led by Antti Latvala, PhD, from the University of Helsinki, in Finland, confirms findings from previous smaller studies on lower resting heart rate as a predictor of adult criminal behavior. The study was published online September 9 in JAMA Psychiatry.

The link between a low resting heart rate and violence has been documented in several studies over the years, but the current study comprises the largest population to date.

Not a Chance Finding

"The finding is not a chance finding," Adrian Raine, DPhil, professor of criminology, psychiatry, and psychology at the University of Pennsylvania, in Philadelphia, who is author of the accompanying editorial, told Medscape Medical News.

Dr Adrian Raine

And with a study population of 700,000 men, the link between low resting heart rate and violent criminality is hard to ignore.

"I found this in my PhD thesis back in 1981," Dr Raine said. "School kids who were antisocial and aggressive had lower resting heart rates. There are many other studies showing the same thing, and the finding by Latvala et al replicates in more than 12 different countries. Their study, however, is by far and away the biggest study ever conducted, and as you see, it is showing that all types of criminal offending, violent offending, drug offending, property offending, even traffic offending are linked to low heart rate.

"So what gives?" he asked. "This is a study of more than 700,000 men. That's a huge number. It forces us to ask, as the authors of this paper do, what is driving this?"

Low HR and Aggressive Behavior in Kids

"Motivation to do this study came from the fact that antisocial and aggressive behavior has been associated with lower resting heart rate in children and adolescents. However, empirical evidence for such an association in adulthood has been very limited," Dr Latvala told Medscape Medical News.

The researchers used data from several Swedish national registries and identified a large dataset of 710,264 Swedish men born between 1958 and 1991.

The men's heart rate was measured at conscription testing for the Swedish military, which was compulsory for all Swedish men at age 18 years until the year 2009.

Using a personal identification number, the researchers were able to link the heart rate information for these men from the conscription register with data from other government registries containing detailed information about crimes, medical treatments, and deaths due to assaults and accidents.

Outcomes were analyzed from January 1, 1973, through December 31, 2009.

In addition, the investigators had various covariate measures available from the conscription testing and from other sources.

The researchers then tested the associations between resting heart rate and later criminal and injury outcomes across an average follow-up period of about 18 years.

The mean resting heart rate (standard deviation [SD]) was 72.2 (12.8) beats per minute.

Compared with 139,511 men in the highest quintile of resting heart rate (≥83 beats per minute), the 132,595 men in the lowest quintile of resting heart rate (≤60 beats per minute) had a 39% higher chance of being convicted of violent crimes (95% confidence interval [CI], 35% - 44%) and a 25% higher chance of being convicted of nonviolent crimes (95% CI, 23% - 28%).

Men in the lowest quintile of resting heart rate were also 39% more likely to have assault injuries (95% CI, 33% - 46%) and unintentional injuries (95% CI, 38% - 41%).

Cardiorespiratory fitness in a subset of 572,610 men did not reduce these associations.

The researchers found similar associations between low systolic blood pressure and violent and nonviolent criminality and assault injuries when systolic blood pressure was studied instead of resting heart rate in more than one million men.

In conclusion, the researchers suggest that resting heart rate and other autonomic measures merit further study as a way of possibly preventing violence and antisocial behavior.

"It would be important to understand better the physiological mechanisms underlying antisocial behavior and violence. Individual differences in these mechanisms could then be used to identify individuals who have an elevated risk for violence," Dr Latvala said.

"Our study confirmed the association between low resting heart rate and subsequent antisocial behavior across adulthood, and now that we know that this is a real association, more detailed research designs ― for example, experimental or genetic research ― can be undertaken to better understand the mechanisms driving this association," Dr Latvala said.

What Gives?

Not everyone with a low resting heart rate becomes violent, noted Dr Raine.

"Low resting heart rate increases the rate of violent crime many years later by 45%, as shown in this study, but why on earth would having a low resting heart rate do this?" he asked.

There are currently two hypotheses to account for the phenomenon.

"One is the fearlessness theory. Some people may commit crime because they are not frightened about the consequences of getting caught. A normal level of anticipatory fear stops many of us from committing crime," Dr Raine said.

Studies in England that measured heart rate in bomb disposal experts in the army found that compared with soldier who were enrolled as control participants, bomb disposal experts had lower resting heart rates.

"Bomb disposal experts are quite fearless. And researchers also found that bomb disposal experts who had been decorated for their bravery have lower resting heart rates than other bomb disposal experts. So you can see how a low resting heart rate reflects a lack of fear and how that might predispose to crime and violence," he said.

The other hypothesis is that low resting heart rate predisposes the individual to seek stimulation.

"The idea here is that heart rate is a matter of arousal. Individuals who impulsively seek stimulation may seek out high-stakes social contexts and make reckless decisions, placing them at risk for being assaulted. For some kids, a way of getting that arousal may be getting into a gang or having a fight," Dr Raine said.

"Violent offending, being injured as a result of violence, and RHR [resting heart rate] come full circle," he concludes in his editorial. "We have known for some time that violent offenders are also injured as a result of violence. Now, the findings by Latvala et al move us to consider low RHR as an unusual suspect underlying this reciprocal association.

"Researchers may consider investing $60 in a heart rate and blood pressure monitor, together with 2 minutes of participant time, to probe further the dual hazards of aggressive behavior and being injured as a result of violence, which are common to a surprising number of psychiatric disorders."

The study was supported by the Swedish Research Council for Health, Working Life and Welfare, the Swedish Research Council, the Swedish Initiative for Research on Microdata in the Social and Medical Sciences, the Academy of Finland, and the Alfred Kordelin Foundation. Dr Latvala and Dr Raine report no relevant financial relationships.

JAMA Psychiatry. Published online September 9, 2015. Abstract, Editorial

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