OBJECTIVE. To examine the effect of adenotonsillectomy (T&A) in children with obstructive sleep-disordered breathing on growth, hyperactivity, and sleep and waking motor activity.METHODS. We studied 54 children who were aged 6 to 12 years and had adenotonsillar hypertrophy and an obstructive apnea-hypopnea index of Ն1 before and 12 months after they all received adenotonsillectomy (T&A). We measured their height, weight, percentage overweight (patient BMI Ϫ BMI at 50th percentile)/ BMI at 50th percentile * 100) and obtained a hyperactivity score from parent report on a standardized behavior questionnaire scale. A subset of 21 of these children were also studied for motor activity by wrist actigraphy for 7 consecutive days and nights before and 12 months after T&A.RESULTS. After T&A, mean obstructive apnea-hypopnea index decreased from 7.6 to 0.6. Height percentile did not change, but weight percentile increased; as a consequence, percentage overweight increased from 32.0% to 36.3%. Hyperactivity scores and total daily motor activity were reduced after T&A. From linear regression, the reduction in hyperactivity scores predicted an increase in percentage overweight. Reduced motor activity was correlated with increased percentage overweight.CONCLUSIONS. An increase in percentage overweight after T&A in children with obstructive sleep-disordered breathing is correlated to decreased child hyperactivity scores and to decreased measured motor activity in the subset studied. These associations suggest that the increase in overweight may be attributable to reductions in physical activity and fidgeting energy expenditure. (OSDB) occurs in ϳ3% of children. 1-3 Adenotonsillar hypertrophy is the most common cause of OSDB in young children, and adenotonsillectomy (T&A) is the primary treatment of obstructive sleep apnea in children. [4][5][6] OSDB in children has been associated with a variety of comorbidities, including hypertension, enuresis, poor scholastic performance, hyperactivity, and attentiondeficit/hyperactivity disorder, and these conditions are also ameliorated with successful treatment of OSDB via T&A. 7,8 OSDB has also been reported to influence somatic growth. Several studies have shown that OSDB is associated with reduced growth in height and weight 5,6,[9][10][11][12] and failure to thrive in infants. 13 These growth alterations have been related to a number of factors, including reduced secretion of growth hormone and insulinlike growth factor-I, 11,14,15 low energy intake as a result of difficulty swallowing, 16 and increased energy expenditure during sleep. 5,16 All of these factors are reported to improve after T&A. 6,11,[14][15][16] Other studies, however, have reported that growth in children with adenotonsillar hypertrophy and OSDB is normal or that these children are actually overweight before treatment. 4,17,18 After T&A, normal-weight and overweight children with or without OSDB rapidly gain weight. 17,18 Thus, although T&A has a beneficial effect on OSDB symptoms 4 and improves the other...