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22-12-2011 | Psychology | Article

ADHD medications not linked to increased risk for adverse cardiac events


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MedWire News: Use of attention-deficit hyperactivity disorder (ADHD) medications in adults is not associated with an increased risk for adverse cardiovascular (CV) events, research suggests.

Lead author Laurel Habel (Kaiser Permanente, Oakland, California, USA) told MedWire News: "While we did not find an increased risk for serious CV events in our study population of young and middle-aged adults, studies such as ours always have some limitations and we cannot completely rule out the possibility that these medications can slightly or modestly increase the risk of these events."

ADHD medications can increase heart rate and blood pressure, he explained.

The team conducted a retrospective population-based cohort study to examine if current use of medications, defined as the period between prescription start date and end of supply, prescribed primarily to treat ADHD is associated with an increased risk for serious CV events (myocardial infarction [MI], sudden cardiac death [SCD], and stroke) in adults aged 25-64 years.

The study used electronic healthcare records from four study sites starting in 1986 at one site and ending in 2005 at all sites. All participants had dispensed prescriptions for methylphenidate, amphetamine, or atomoxetine at baseline.

Each of the 150,359 medication users was matched to two nonusers (no current use and no use in the year before enrollment) on the basis of study site, birth year, gender, and calendar year.

The incidence of serious CV events was then compared between current or new users (no use in the year before baseline) and remote users (greater than 364 days since end of last days supply) to account for potential healthy-user bias.

During 806,182 person-years of follow-up there were 1357 cases of MI, 296 cases of SCD, and 575 cases of stroke.

There were 107,322 person-years of current use, with a crude incidence per 1000 person-years of 1.34 for MI, 0.30 for SCD, and 0.56 for stroke.

In analysis adjusted for matching variables only, the rate ratio (RR) of MI, SCD, or stroke for current versus nonuse of ADHD medications was 0.97. After also adjusting for CV risk score, the RR was modestly lower, at 0.83.

However, this apparent protective association was likely due to "healthy-user bias," stemming from an overrepresentation of White, college-educated individuals among current users, write the authors in JAMA.

For current versus remote use, the RR for the combined endpoint was 1.02. The upper bound of the confidence interval was 1.28, corresponding to an additional 0.19 events per 1000 person-years at ages 25-44 years and an additional 0.77 events per 1000 person-years at ages 45-64 years.

"Our results for periods of current use versus periods remote from last use suffer less from the [healthy-user] bias - and these results do not suggest that ADHD mediations are cardioprotective," Habel pointed out.

"Healthy user bias is a common and well known potential bias in studies such as ours."

Editorialist Philip Shaw commented: "Perhaps the greatest clinical influence of the study by Habel et al will be in how clinicians counsel patients regarding the risk and benefits of ADHD medications."

"Now there is solid evidence - perhaps even some heartening news - that physicians can use to address concerns about CV risk."

Habel agreed: "Our findings may be useful to doctors and patients who are currently taking ADHD medications - or considering taking these medications."

By Piriya Mahendra

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