Actigraph placement and sleep estimation in children.

STUDY OBJECTIVES: To determine whether actigraph placement affects sleep estimation in children. DESIGN: Descriptive study. SETTING: Naturalistic setting. PARTICIPANTS: Twenty children aged 7-12 years from primary schools. INTERVENTIONS: N/A. MEASUREMENTS: Motor activity was measured from the waist and non-dominant wrist with actigraphs for three consecutive days during a school week. RESULTS: The minute-by-minute agreement of sleep-wake states between the two measurement sites was 92.5%. Wrist- and waist-recorded sleep parameters correlated well and the mean values did not differ. CONCLUSIONS: Although the placement of the actigraph slightly affected the measured activity parameters, its influence on 3-night mean sleep estimates in children was not statistically significant.

Working memory and sleep in 6- to 13-year-old schoolchildren.

OBJECTIVE: To study the associations between sleep quality/quantity and performance in auditory/visual working memory tasks of different load levels. METHOD: Sixty schoolchildren aged 6 to 13 years from normal school classes voluntarily participated. Actigraphy measurement was done during a typical school week for 72 consecutive hours. It was timed together with the working memory experiments to obtain information on children's sleep during that period. The n-back task paradigm was used to examine auditory and visual working memory functions. RESULTS: Lower sleep efficiency and longer sleep latency were associated with a higher percentage of incorrect responses in working memory tasks at all memory load levels (partial correlations, controlling for age, all p values < .05, except in visual 0-back and auditive 2-back tasks); shorter sleep duration was associated with performing tasks at the highest load level only (partial correlations, controlling for age,p < .05). Also in general linear models (controlling for age, gender, and socioeconomic status), sleep efficiency (F = 11.706, p = .050) and latency (F = 3.588, p = .034) were significantly associated with the mean incorrect response rate in auditory working memory tasks. CONCLUSIONS: Sleep quality and quantity affect performance of working memory tasks in school-age children. In children with learning difficulties the possibility of underlying sleep problems should be excluded.

Day length associates with activity level in children living at 60 degrees north.

The associations between day length and activity, rest-activity rhythm, and psychiatric symptoms were studied. Sixty-six healthy children participated in the study during one year. They were monitored for 72 consecutive hours with belt-worn activity monitors (actigraphs) to obtain objective data on their activity levels during the day and night. In addition, the parents filled out the Child Behavior Checklists. It was found, that the mean total and day and night time activity levels were increased and the relative circadian amplitude blunted with the longer day length. It was concluded that day length was associated with activity level and rest-activity rhythm and this association may reflect the seasonal changes in these parameters.

Audiospatial and visuospatial working memory in 6-13 year old school children.

The neural processes subserving working memory, and brain structures underlying this system, continue to develop during childhood. We investigated the effects of age and gender on audiospatial and visuospatial working memory in a nonclinical sample of school-aged children using n-back tasks. The results showed that auditory and visual working memory performance improves with age, suggesting functional maturation of underlying cognitive processes and brain areas. The gender differences found in the performance of working memory tasks suggest a larger degree of immaturity in boys than girls at the age period of 6-10 yr. The differences observed between the mastering of auditory and visual working memory tasks may indicate that visual working memory reaches functional maturity earlier than the corresponding auditory system.