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Stimulant use predicts higher BMI trajectory in children with ADHD

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August 23, 2017

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April Bowling

Children with ADHD prescribed stimulant therapy before fifth grade are more likely to have a higher BMI in early adolescence than children who do not receive medication or those who do not have the disorder, according to findings published in Obesity.

In a cross-sectional study, the researchers noted that young children with ADHD prescribed medication can experience reduced growth rates for up to 2 to 3 years, but there is a paucity of evidence regarding any longitudinal associations of more than 3 years between stimulant use and BMI trajectory.

“Unlike those who aren’t medicated, children with ADHD who begin stimulants prior to fifth grade have small, but significantly greater increases in BMI between fifth and eighth grade relative to children who do not have ADHD,” April Bowling, MA, ScD, assistant professor of health sciences at Merrimack College in North Andover, Massachusetts, told Endocrine Today. “This association persists even when we control for the symptoms that might have led to that medication use in the first place. These findings echo other long-term longitudinal analyses which found that children who started stimulants in childhood had increased BMI trajectories by late adolescence.”

Bowling and colleagues analyzed data from 8,250 children participating in the Early Childhood Longitudinal Study 1998-1999 kindergarten cohort, a prospective, observational study of kindergartners and their parents, teachers and schools conducted by the National Center for Education Statistics. Data collection took place in kindergarten and first, third, fifth and eighth grades; in each wave, parents were asked whether their child had a diagnosis of ADHD. Parents of children diagnosed with ADHD were asked whether the child was taking prescription medicine and, if so, for how long. Researchers assessed behavior, dietary patterns (including sugar-sweetened beverage intake) and physical activity via surveys and calculated BMI and BMI z score. Researchers modeled BMI and z score change by ADHD and stimulant start time, examined the odds of unhealthy diet and physical activity predicted by ADHD and stimulant use, and performed mediation analysis assessing any indirect effects of health behaviors.

Within the cohort, 650 children (8%) had ADHD; 380 of those children were prescribed medications to manage symptoms. Among those prescribed medication, 60 were taking medication by first grade; 120 started medication between first and third grade; and 190 started taking medication between third and fifth grade. Researchers observed a lower mean BMI in fifth grade among children with ADHD taking medication when compared with children with ADHD not taking medication or those without the disorder (P < .001); by eighth grade, there were no between-group differences for BMI.

In models using medication start time as a predictor of BMI, researchers found that starting medication before first grade was positively associated with increased BMI change from fifth to eighth grade; starting medication between first and third grade was associated with a nearly 1.2 kg/m² greater increase in BMI change from fifth to eighth grade; and beginning medication between third and fifth grade was positively associated with BMI increases from fifth to eighth grade.

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“For all three medication start times, this association translated to about a 0.3 SD increase in children’s BMI z score from fifth to eighth grade, while children with unmedicated ADHD experienced the same rate of growth as those without an ADHD diagnosis,” the researchers wrote. Adjustment for sex or baseline overweight or obesity did not change the associations.

Researchers also found that children who had ADHD and were taking medication by fifth grade were more likely to have low parent-reported physical activity levels compared with children without ADHD (adjusted OR = 1.27; 95% CI, 1.02-1.59); researchers did not observe this association in children with ADHD who were not taking medication.

Children with ADHD had higher odds of poor diet regardless of medication. After adjusting for medication use, health behaviors were not associated with BMI change, according to researchers.

The other major takeaway from our study is that in this large, diverse sample of children, those with ADHD are at greater risk of poor dietary patterns than children without the diagnosis,” Bowling said. “That increased risk was present regardless of their medication status and after controlling for a variety of other potential confounders.

“Given longitudinal evidence, stimulants should not be viewed as tools to reduce obesity risk among children with ADHD, at least until additional research is conducted,” the researchers wrote. “Conversely, there is not enough evidence to suggest that future obesity risk should deter prescriptions indicated to treat ADHD’s behavioral symptoms. Because children with ADHD appear to be at a higher risk of poor dietary intake regardless of medication use, clinicians should consider lifestyle counseling following an ADHD diagnosis regardless of baseline weight status.” – by Regina Schaffer

Disclosures: The authors report no relevant financial disclosures.

itj+ Perspective

Alana Rodriguez
Perspective

This is a timely study examining BMI in relation to medication use for attention deficit hyperactivity disorder (ADHD). Growth is an important indicator of child health, and helping children reach optimal growth and growth rate is a goal for pediatricians. Further, childhood growth is associated with several negative outcomes across the life course, including risk for obesity and metabolic disease. Moreover, the impact of ADHD medication on growth has been debated for some time.

Important strengths of the study include its longitudinal design and use of a large-scale, nationally representative cohort, ECLS-K. Thus, it adds considerable new knowledge on long-term associations from childhood to adolescence between BMI and medication use. However, as an initial, large-scale, observational study, many questions remain to be explored and tested in future research. Bowling and colleagues considered the start time of medication; however, an even larger sample size is needed to conduct subgroup analyses that consider the differential impact of medication in relation to individuals’ age of adiposity rebound, peak height velocity  and Tanner stage. These times of intense growth may be critical.

It would be beneficial for future studies to separate BMI in its components of height and weight. In the most recent follow-up of the Multimodal Treatment Study of Attention Deficit/Hyperactivity Disorder (Swanson JM, et al. J Child Psychol Psychiatry. 2017; doi: 10.1111/jcpp.12684. doi: 10.1111/jcpp.12684), Swanson and colleagues reported that the cost of ADHD medication is growth suppression of final adult height. Bowling and colleagues report higher BMI trajectory in adolescence. Could this be due to reduced height? Alternatively, could this be due to increased risk of obesity? Interestingly, Bowling and colleagues do not find differences in diet or physical activity among children with ADHD. Thus, the question of whether children who are diagnosed with ADHD are shorter already before medication is initiated remains an issue for further study.  

Alina Rodriguez, PhD

Professor of Psychology,
University of Lincoln School of Psychology,
Lincolnshire, UK Visiting professor,
Department of Epidemiology and Biostatistics, School of Public Health,
Imperial College London

Disclosure: Rodriguez reports no relevant financial disclosures.