Objective measurement of motor activity during cognitive performance in adults with attention-deficit/hyperactivity disorder

S. Lis1, N. Baer1, C. Stein-en-Nosse1, B. Gallhofer1, G. Sammer1, P. Kirsch1,2
Article first published online: 25 FEB 2010

DOI: 10.1111/j.1600-0447.2010.01549.x

© 2010 John Wiley & Sons A/S
Issue
Acta Psychiatrica Scandinavica
Volume 122, Issue 4, pages 285–294, October 2010
Additional Information(Show All)
How to CiteAuthor InformationPublication History
Keywords:
attention-deficit disorder with hyperactivity;motor activity;cognition;actigraphy

Abstract
Lis S, Baer N, Stein-en-Nosse C, Gallhofer B, Sammer G, Kirsch P. Objective measurement of motor activity during cognitive performance in adults with attention-deficit/hyperactivity disorder.

Objective:  This study investigates whether hyperactivity, i.e. an increased level of motor activity, can be observed in adults with attention-deficit/hyperactivity disorder (ADHD).

Method:  An infrared motion-tracking system was used to measure motor activity in 20 unmedicated adults with ADHD and 20 matched healthy controls (HC) during a 1-back working memory task.

Results:  Motor activity was higher in ADHD. It increased with the duration of testing and co-varied with cognitive performance in ADHD only. Subjective and objective measurements of motor activity were related in HC, but not in ADHD.

Conclusion:  Higher levels of motor activity in ADHD are objectively measurable not only in children, but in adults as well. It is linked to cognitive performance arguing against distinguishable diagnostic subtypes. The objective measurement of motor activity seems to extend the description of ADHD symptoms derived from rating scales and might thus help to bridge the gap between psychopathological symptom description and neurobiological alterations.

Significant outcomes
•
 A higher level of motor activity can be measured objectively in attention-deficit/hyperactivity disorder (ADHD) not only in children, but in adults as well. Differences between ADHD patients and healthy subjects increase with the duration of a cognitive testing situation.
•
 A higher level of motor activity is accompanied by more severe cognitive impairments in ADHD.
•
 In contrast to healthy subjects, ADHD patients fail to assess their level of motor activity.
Limitations
•
 The assessment of motor activity was limited to motion tracking of a headband reflector attached to the forehead without including additional measurements of hyperactivity derived from additional reflectors or actigraphy.
•
 Motor activity was measured during a standardised cognitive testing situation only.
•
 The relatively small sample size prevented a detailed analysis of alterations in subtypes of attention-deficit/hyperactivity disorder.

Introduction
Besides attention deficits and impulsiveness, hyperactivity constitutes one of the core symptoms of attention-deficit/hyperactivity disorder (ADHD, 1). It is defined as an excessive or developmentally inappropriate level of motor or vocal activity. According to DSM IV, symptoms of hyperactivity in children include such behaviours as fidgeting with hands or feet, squirming in seat, leaving seat in situations in which remaining seated is expected, running about, climbing excessively and acting as if driven by a motor.

In child ADHD, a multitude of studies have objectively measured alterations in activity level applying actigraphy and motion-tracking systems. They have been used to discriminate children with ADHD from healthy ones (2–4), to evaluate pharmacological treatments (5–7), to improve hyperactivity in feedback trainings (8) and to relate symptoms to neurobiological alterations (9).

Attention-deficit/hyperactivity disorder has traditionally been regarded as a childhood disorder; however, in up to 80% of the affected children the disorder persists into adulthood (10). In contrast to impulsiveness and attention deficits that are assumed to persist into adulthood, the severity of hyperactivity is regarded to change over the span of life, i.e. to attenuate with increasing age (11). The gross motor overactivity observable in children is assumed to change towards greater difficulties with fidgeting and a more subtle sense of restlessness in adults with ADHD. Nevertheless, 74% of adults with ADHD report frequently fidgeting with their hands or feet and 66% complain of having difficulties remaining seated (12). In contrast to the well-established use of objective measurements of motor activity in children, the assessment of the severity of hyperactivity relies in adults primarily on the subjective ratings based upon questionnaires. Generally, these subjective measurement procedures are weakened by the fact that they might be biased by comparison standards or phenomena like the Halo-effect (13), which in turn often results in low inter-rater reliabilities (14, 15).

Only two studies have applied actigraphic methods to investigate motor activity in adult ADHD (16, 17). While both studies point to an objectively measurable higher level of motor activity in adults with ADHS, the validity of their data is limited due to some methodological limitations. Tuisku et al. (17) had analysed an atypical sample as their subjects had primarily been diagnosed as antisocial offenders and the diagnosis of ADHD had not been confirmed according to established procedures. Boonstra et al. (16) had measured motor activity in a naturalistic setting over a period of 7 days by means of actigraphy and found a 17% elevated daytime activity level. However, non-standardised settings have the disadvantage that actigraphic parameters might be influenced by everyday activities. To control for this, Boonstra et al. coded the participants’ occupation and the physical load of their activities and found no differences between patients and controls. Nevertheless, there remains some uncertainty regarding the sharpness of coding and whether all factors that might influence motor activity were taken into consideration. An alternative approach might be to register motor activity during a standardised cognitive testing situation to control for the effect of different professions or leisure-time activities. Although this might constitute an artificial situation, the recording of motor activity during cognitive task solving has shown to be especially suited to identify differences in motor activity between groups in children with ADHD (18, 19). Additionally, a testing situation might be appropriate to simulate those situations in daily living as e.g. office work during which an increased level of motor activity might result in problems because relative rest is expected by a social environment. Beyond that, the simultaneous measurement of motor activity and cognitive functioning allows an analysis of the relationship between the level of motor activity and alterations in cognitive functioning.

http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0447.2010.01549.x/full