estover and Halm et al, BMC Cardiovasc Disord.2012;12:41 ) showed an increased risk in 1 of 7 studies in children and adolescents and in 2 of 3 studies involving adults.
Dr. Dalsgaard and colleagues report that although their new findings are consistent with the 1 study in the review showing an increased risk (Winterstein et al. 2007), their observation period was significantly longer (9.5 vs 2.3 years), which likely explains the finding of a higher risk (HR, 2.2 vs 1.2).
Commenting on the study’s findings for Medscape Medical News, Arthur N. Westover, MD, of the Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, and lead author on the 10-study review, suggested that another explanation for the higher risk could be the inclusion of a broad scope of cardiovascular events.
“The investigators used a very broad outcome, essentially any kind of cardiovascular event, whether serious or not,” he said.
“When you broaden the outcome to include any kind of cardiovascular event, you are more likely to find a signal, but less able to determine whether it is clinically meaningful,” he said.
“For example, in the study, 40% of the cases were ‘cardiovascular disease not otherwise specified,’ ” he noted. “For a clinician or patient, it may be hard to interpret what that means.”
In contrast, he noted, another prominent study that looked at only serious cardiovascular events, including stroke, heart attack, and sudden death (Cooper, et al, N Engl J Med. 2011;365:1896-1904 ), which was reported by Medscape Medical News, did not find an increased risk.
Likewise, the new study also did not show an increased risk for death or serious cardiovascular events among stimulant users, Dr. Westover pointed out.
Mark Olfson, MD, MPH, professor of psychiatry at Columbia University Medical Center in New York City, and lead author on another of the studies included in Dr. Westover’s review ( J Am Acad Child Adolesc Psychiatry. 2012;51:147-56 ), added that an important limitation of the new study is a lack of information on other therapies that patients received.
“In contrast to most pharmacoepidemiological studies on this topic, the new study finds an association between stimulant treatment and a wide range of cardiovascular events,” he told Medscape Medical News.
“However, without more information on the other medications that the patients were receiving, such as corticosteroids, erythromycin, and oral contraceptives, and the distribution of known disease risk factors, such as prothrombotic states, hyperlipidemia, asthma, and obesity, it is difficult to evaluate the clinical significance of the current findings.”
Among the key challenges in any of the efforts to evaluate cardiovascular risk associated with ADHD psychostimulants is the simple fact that such events, though serious when they do occur, are still highly uncommon, Dr. Olfson added.
“Cardiovascular events in ostensibly healthy young people with ADHD are thankfully quite rare,” he said.
“The [events’] uncommonness has made it exceptionally difficult to determine who is at risk for these potentially catastrophic events.”
The authors and Dr. Olfson report no relevant financial relationships. Dr. Westover reports that he is the recipient of a National Institutes of Health grant for research into ADHD drug risks.
J Child Adolesc Psychopharmacol. Published online June 23, 2014. Full text