The Cooper Institute
 

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH

 
 

ADHD, Stimulant Use, and Cardiovascular Responses to Maximal Exercise

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Live well

Monday, Feb 26, 2018

Over the past two decades, an increasing number of adults have been diagnosed with attention–deficit/hyperactivity disorder (ADHD). This condition is characterized by a short attention span, impulsive behavior, and hyperactivity. The most common method of treatment for ADHD are stimulant drugs, which help to increase the levels of chemicals in the brain called neurotransmitters. Among these are serotonin, dopamine, and norepinephrine. Neurotransmitters allow various regions of the brain to communicate with one another better, which in turn decreases the symptoms of ADHD. Because of  some data showing a small increased risk of ventricular arrhythmia and sudden death among adult stimulant users, there has recently been a much stronger focus on the cardiovascular safety of these medications. For example, Cooper Institute researchers, along with their colleagues at UT Southwestern Medical Center became interested in how the cardiovascular system of stimulant users responded during and following maximal exercise. We will now summarize findings from two of their studies.  

STUDY 1: MAXIMAL TREADMILL TEST

In 2015, 245 Cooper Clinic patients with ADHD who were taking stimulants were matched with a control group of 735 patients who did not have ADHD and were not taking stimulants. All participants underwent a maximal treadmill exercise test. One of the important variables measured during the treadmill test is maximal heart rate (MHR), which is simply the highest heart rate that is attained.

MHR is highly dependent on age, and can be predicted by using the formula 208 – (0.7 x age).
For example, the predicted MHR for a 40 year old is 208 – (0.7 x 40) = 180 beats/minute.

The inability to reach at least 80% of the predicted MHR during a maximal exercise test is known as chronotropic incompetence, which is linked to serious cardiovascular events. The group taking stimulants was 3.3 times more likely to have chronotropic incompetence than the control group. The researchers emphasized that the clinical significance of this finding among those using stimulants needs further investigation.


STUDY 2: RECOVERY PERIOD

The group then decided to further analyze the data, specifically examining what occurred during the recovery period of the treadmill test for these same individuals. In a healthy patient, heart rate decreases substantially during the first minute of recovery from maximal exercise.

For this study, a normal heart rate recovery was defined as more than a 12 beats/minute decrease from the time of exhaustion until 1 minute post-exercise. For example, if the maximal heart rate during the treadmill test was 185 beats/minute and the 1 minute recovery heart rate was 170 beats/minute, then the difference of 15 beats/minute represents a normal heart rate recovery. On the other hand, if the maximal heart rate was 185 beats/minute and the 1 minute recovery heart rate was 175 beats/minute, then the difference of 10 beats/minute represents an abnormal heart rate recovery.

A similar type of grading system was set up to gauge normal versus abnormal blood pressure recovery response. Once again, the cardiovascular responses of the stimulant group were significantly different from the responses of the control group.Stimulant users were nearly twice as likely to have abnormal heart rate recovery and abnormal blood pressure recovery values than the control group. These abnormal responses were actually more common in those who reported high levels of physical activity than in those who reported low levels of activity.


CONCLUSION

The authors concluded that the autonomic nervous system is altered by the use of stimulants, and that this might help explain the small increased risk of ventricular arrhythmias in adults with ADHD who are treated with stimulants. It is important to note that these results should not in any way discourage ADHD individuals who are taking stimulants to avoid regular and moderate bouts of physical activity. Additionally, patients with ADHD should continue to take their medication per their doctor’s instructions.    


References
Westover, A., Nakonezny, P., Barlow, C., Vongpatanasin, W., Adinoff, B., Brown, E., Mortensen, E., Halm, E., DeFina, L. (2015). Exercise outcomes in prevalent users of stimulant medications. Journal of Psychiatric Research, 64:32-39.

Westover, A., Nakonezny, P., Barlow, C., Adinoff, B., Brown, E., Halm, E., Vongpatanasin, W., DeFina, L. (2016).  Heart rate recovery and systolic blood pressure recovery after maximal exercise in prevalent users of stimulant medications. Journal of Clinical Psychopharmacology, 36(3).   




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