The use of drugs for attention-deficit/hyperactivity disorder (ADHD) was not associated with an increased risk of serious cardiovascular events like heart attack and stroke in young and middle-age adults, researchers found.
In fact, the rate of heart attack, sudden cardiac death or stroke was significantly lower in current users of the drugs compared with nonusers, according to Laurel Habel of Kaiser Permanente Northern California in Oakland and colleagues.
But that finding, reported online in the Journal of the American Medical Association, was likely the result of a healthy-user bias stemming from an overrepresentation of white, college-educated individuals among current users, the authors noted.
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The findings are consistent with the researchers' parallel study in users of ADHD medications, ages 2 to 24, that was reported last month.
Over the past decade, the use of ADHD medications has increased more rapidly in adults than in children. In 2005, adults accounted for about one-third of issued prescriptions.
Some of the use could be for other conditions, however, as stimulants are approved for narcolepsy and may be used off-label for obesity and fatigue related to depression, stroke, or traumatic brain injury.
Because the medications increase heart rate and blood pressure, there have been concerns about possible adverse cardiovascular effects that have persisted despite epidemiological studies mostly refuting such an association.
In parallel with the study in children, teens, and young adults, Habel and colleagues examined the association between use of ADHD medications and the occurrence of MI, stroke, and sudden cardiac death in adults ages 25 to 64.
They retrospectively analyzed data using electronic healthcare records from four sources -- OptumInsight Epidemiology, Tennessee Medicaid, Kaiser Permanente California, and the HMO Research Network.
Follow-up started from 1986 to 2002 and ended in 2005.
The researchers identified 150,359 individuals who had filled a prescription for methylphenidate, amphetamine, atomoxetine, or pemoline (Cylert) at baseline and matched them to 292,839 nonusers by study site, birth year, sex, and calendar year.
Most of the prescriptions were for methylphenidate (45 percent) and amphetamine (44 percent), with small proportions receiving atomoxetine (8 percent) and pemoline (3 percent).
During 806,182 person-years of follow-up, there were 1,357 heart attacks, 296 sudden cardiac deaths, and 575 strokes overall.
After adjusting for other potential confounders, there was no increase in cardiovascular risk associated with current use of ADHD medications, which was consistent for specific medications and across endpoints. The findings were similar when the analysis was restricted to new users.
Although the study did not show evidence of an elevated cardiovascular risk, the authors noted several limitations of the study, including the use of electronic pharmacy records to determine medication use, the lack of dose data, the exclusion of adults 65 and older, possible misclassification of some of the endpoints, and the limited ability to adjust for some factors, including psychiatric conditions and medications.
ADHD Drugs Safe for Adult Hearts
There was also only moderate statistical power for several comparisons, they wrote.
"A modestly elevated risk cannot be ruled out, given limited power and a lack of complete information on some potentially important risk factors and other factors related to use of these medications," Habel and colleagues wrote.
In an accompanying editorial, Dr. Philip Shaw of the National Human Genome Research Institute in Bethesda, Md., pointed out that any possible absolute risk increase is small.
"Now there is solid evidence -- perhaps even some heartening news -- that physicians can use to address concerns about cardiovascular risk," Shaw wrote.
But, he said, "the study does not obviate either the need for a thorough history and examination of all patients prior to starting any ADHD medications or the need for ongoing evaluations. Psychostimulants have many noncardiovascular adverse effects that must be monitored, including weight loss, appetite suppression, and insomnia."