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A too-fast heartbeat in early adulthood is a warning sign for increased risk of cardiovascular problems decades later on, a Japanese study suggests.

The study of 614 residents of a rural farming community in southwestern Japan found that a heart rate greater than 80 beats a minute during a first examination in 1979 predicted the development of obesity and diabetes, which contribute to heart problems.

The findings, from Kurume University School of Medicine, were published online Dec. 11 in the American Journal of Hypertension.

A fast heart rate is a signal from the sympathetic nervous system, a part of the autonomic nervous system, which is the body’s automatic pilot that governs instinctive responses, explained Mercedes Carnethon, assistant professor of preventive medicine at Northwestern University’s Feinberg School of Medicine. She found the same rapid heartbeat association in a group of Americans she studied.

“If someone has a consistently fast heart rate, it is because of increased input from the sympathetic part of the nervous system because the body is preparing to respond to stress,” Carnethon said. “There is an increase in levels of blood glucose — essentially because the body is storing energy to prepare for fight or flight, so that predisposes to diabetes.”

Carnethon’s study followed Chicago residents even longer than the Japanese researchers. “Over a 33-year follow-up, we showed that people with a higher heart rate were more likely to have Medicare claims for diabetes-related conditions,” she said.

There’s a possible clinical use for the findings, Carnethon said, since doctors routinely listen to the heart rate.

“It is a very simple measure, regularly taken in clinical practice, that could be potentially useful because it suggests where there might be a higher incidence of heart risk and mortality,” she said. “It is a first stage to alert the clinician that there might be something worth investigating.”

The similar findings in the two studies half a world apart are noteworthy, Carnethon said. “We are always happy to see findings replicated by different investigators in different settings,” she said.

Meanwhile, researchers are reporting a different built-in mechanism that protects a lucky few individuals from heart disease — a genetic mutation that seems to reduce blood levels of the fats called triglycerides.

The mutation was found in members of the Old Order Amish community in Pennsylvania, said the lead investigator, Toni I. Pollin, an assistant professor of medicine at the University of Maryland School of Medicine.

Pollin and her colleagues looked through the complete genetic complement of more than 800 members of the Amish community. “We looked at genes involved in the response to dietary fat,” she said. “One region came up strong on chromosome 11. This genetic marker was not too far from a cluster of genes involved in lipid metabolism.”

The researchers closed in on one gene, designated APOC-3, according to a report in the Dec. 12 issue of the journal Science. That gene makes a protein that inhibits the breakdown of triglycerides. About 5 percent of the Amish in the study had a mutated form of the gene that limited production of the protein, and so they had low blood lipid levels.

“It is an apparent cardioprotective mechanism,” Pollin said. “It raises the hope that by decreasing production of APOC-3 it could potentially be therapeutic.”

It’s possible that a drug designed to target the gene could be used to reduce levels of blood fats and thus reduce coronary risk, Pollin said.

The mutation has not been found outside the Amish community, Pollin said. “We have looked at 200 healthy individuals and have not found it, she said.

High heart rates linked to obesity, diabetes

High resting heart rates may be linked to the development of obesity and diabetes, a Japanese study shows.

Heart rate is regulated by the sympathetic nervous system (SNS), a network of neurons in the body operating without conscious thought. It is also believed to affect the large intestine, blood vessels, pupil dilation, perspiration and blood pressure.

In an article published in the American Journal of Hypertension, researchers in Japan said people with resting heart rates of over 80 beats per minute had higher odds of developing insulin resistance, diabetes and cardiovascular problems.

The project was one of the first studies to assess the impact of higher heart rates on the body’s metabolism. It involved 614 participants who were followed over a period of 20 years.

The participants were divided into four groups: those with heart beat rates of under 60, 60-69, 70-79 and over 80.

Compared to those with heart rates of under 60, those who had rates of more than 80 were 1.34 times more likely to be obese, 1.2 times more likely to develop insulin resistance and 4.39 times more likely to end up diabetic.

“These findings provide a mechanism that might explain how obesity and the SNS are linked. This may, in turn, increase understanding of their causal role in the development of heart attack and stroke, the leading causes of death worldwide,” the researchers said in a statement.

The researchers believe that excessive nerve activities may lead to obesity because they lower the amount of fat burn in the body.