(CNN) Heart failure tied to use of methamphetamines is on the rise among US veterans, suggests a preliminary study presented Tuesday at the annual scientific meeting of the American Heart Association.

Meth is chemically similar to the nervous system stimulant amphetamine. It is typically inhaled or smoked, swallowed, snorted or injected once dissolved in water or alcohol. More than 4.7% of Americans report trying this drug at least once, according to the National Institute of Drug Abuse.

"Methamphetamine is an addictive drug, which could have a wide range of effects on patients' physical and mental well-being," said Dr. Marin Nishimura, the study author and internal medicine resident at the University of California, San Diego. "In addition to the heart, methamphetamine has been shown to have toxic effects on the brain."

Thousands of veterans studied

Nishimura and her team became interested in meth-associated heart failure "because we noticed that we have been seeing increasing cases of this condition in the hospital where we practice."

They reviewed the medical records of heart failure patients at San Diego VA Medical Center between 2005 and 2015 to see which had used meth. All told, the team looked at records for 9,588 patients and found 480 with a documented history of meth abuse.

"The proportion of patients that used methamphetamine was increasing from 2005 to 2015," Nishimura said: from 1.7% of total heart patients at this facility in 2005 to 8% in 2015.

Patients in the two groups -- users and non-users of meth -- had striking differences, she said.

"Heart failure patients with methamphetamine abuse were younger, more likely to be homeless, unemployed and diagnosed with other substance-abuse and psychiatric conditions," Nishimura said.

On average, the meth users with heart failure were 61 years old. This is considerably younger than the average age of non-meth-using heart failure patients at the facility: 72 years old. Meth users were also more likely to have post-traumatic stress disorder and depression.

In addition, meth users were less likely to have atrial fibrillation -- an irregular heartbeat that can lead to blood clots, stroke and heart failure -- than non-meth users.

And, compared with non-using VA heart patients, those who used meth were less likely to have significant coronary artery disease yet tended to visit the ER more frequently.

Nishimura believes she and her colleagues need to address these issues to better take care of VA patients. "Furthermore, these differences may give us a clue as to when we should be screening for methamphetamine use when patients are newly diagnosed with heart failure," she added.

Still, more research is needed, because the findings are based solely on a small number of veterans at a single medical center in San Diego, which means the study is too limited, she cautioned.

'Vulnerable population'

Dr. Harshal Kirane, director of addiction services at Staten Island University Hospital in New York, said the new study "is yet another call to address the challenging needs of US veterans." Kirane was not involved in the research.

"Methamphetamine use is associated with numerous well-established health consequences in essentially all systems of the body," he said, adding that "methamphetamine-associated cardiomyopathy," in which the heart muscle deteriorates as a result of meth use, is still only "partially understood."

Slightly more than 5% of the heart failure hospitalizations in the US are attributable to stimulant use, he said.

Meanwhile, patterns of drug use continuously evolve, he noted, "as well as the potential for medical consequences from drug use."

"Military veterans are an especially vulnerable population for developing mental health and substance use issues," Kirane said.

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He added that the new research "raises important questions" about why veterans may be using methamphetamine and what challenges they face in "accessing care for substance use disorders and general medical issues."

"It also raises questions about the underlying biology of the heart that may make some individuals exquisitely vulnerable to developing heart failure from methamphetamine use," he said.

The fact that potent illicit drugs can be manufactured from over-the-counter medications "has contributed to increased methamphetamine use in regions of the country less accessible to major drug trafficking pathways such as rural communities," Kirane said.

Though it's "unclear" why an increase in meth use has occurred among veterans, Nishimura agrees with Kirane's basic assessment.

"What's certainly contributing to the current popularity is likely due to the fact that it can be synthesized in small-scale laboratories," she said. "And sold at relatively low street prices."