Actigraphy, as a measure of sleep, is most accurate when used to differentiate major periods of sleep and waking. Short periods of sleep and wakefulness are much more difficult to recognize actigraphically than are long ones. The sleep parameters most closely estimated by actigraphy are sleep duration, sleep efficiency, and waking after sleep onset. Even these parameters are difficult to assess, however, because they are very sensitive to individual differences in sleep and movement patterns. Depending upon these individual characteristics and patients' specific clinical problems, the correlation of actigraphically determined sleep parameters with actual sleep measurements may vary from good to poor.
Sleep latency is more difficult to estimate.
When the severity of a sleep disturbance reported by the patient or caretaker seems inconsistent with clinical impressions or laboratory findings. Technical considerations Actigraphic studies should be conducted for a minimum of three consecutive 24-hour periods. Interpretation must be done manually by visual inspection following procedures outlined, and algorithms validated for, the specific device in use. Automatic scoring may be used in addition to manual methods of scoring. The role of actigraphy in the evaluation of sleep disorders.