Introduction Actigraphy is a valid measure to assess sleep and circadian rhythm abnormalities. It is listed in the diagnostic criteria for several sleep disorders where single night polysomnography is insufficient (ICSD-2). However, the optimal recording time for measurement remains unclear. We hypothesised that 7 days would provide similar data as recording for 14 days.
Patients & Methods We analysed 3 consecutive years of actigraphy data obtained within a tertiary sleep referral centre. Data were recorded continuously for two weeks using the AW2 Actiwatch (Cambridge NeuroTechnology, UK), using Actiwatch Sleep Analysis 5 software for analysis of the data. Parameters, including sleep efficiency (SE), sleep latency (SL), sleep fragmentation index (SFI), total sleep time (TST) and wake after sleep onset (WASO), were classified into week 1, week 2 and an overall average for the duration of 14 days. In addition, two experienced consultants working in the sleep laboratory compared the results of week 1 vs. week 2 independently, visually analysing the data for circadian rhythmicity and fragmentation of the pattern; allowing calculation of the itraclass correlation coefficient (ICC), κ.
Results The actigraphies of 239 patients (51.9% (124) male; mean age 42 (16) years) were analysed. There was no difference in SE, SL, SFI or WASO between week 1, week 2 and 14 days average recording. A difference was found between TST week 1 (399.9, 95% CI 389.9–409.9 mins) and TST week 2 (388.7, 95% CI 378.3–399.1 mins), but not between TST for 14 days average recording and either week (394.3, 95% CI 384.7–403.9 mins). Independent scorers achieved a strong agreement in the rhythmicity of the sleep pattern (ICC κ 0.734, p<0.001) and a low agreement for the fragmentation of the pattern (ICC κ 0.380, p<0.001).
Conclusion One week of actigraphy provides similar data to two week actigraphy, despite subtle differences between different weeks. One week actigraphy should be recommended as standard to maximise efficiency of the clinical service.