Development and preliminary validation of the Chinese version of the Sleep-Associated Monitoring Index

Abstract

Objective: To examine the psychometric properties of the Chinese version of the Sleep-Associated Monitoring Index (SAMI) in Taiwanese haemodialysis patients.

Design: An instrument translation and validation study.

Setting: A haemodialysis (HD) unit in a university-affiliated medical centre in northern Taiwan.

Participants: 206 patients who were 18 or above, diagnosed with end-stage renal disease and under maintenance HD twice or thrice a week, 3 h or more per session for more than 3 months.

Methods: A principal component analysis was used to examine the construct validity of the SAMI. The participants were classified into poor (n=160) and good sleepers (n=46) using a cut-off value of 5 on the Pittsburgh Sleep Quality Index (PSQI). All participants filled out the Beck Depression Inventory (BDI) and Back Anxiety Inventory (BAI) along with the SAMI. Internal consistency was examined by the Cronbach's α. To assess test-retest reliability, the participants were asked to fill out the SAMI on a second occasion at a 2-week interval.

Results: Eight subscales emerged from the principal component analysis. Individual with insomnia had significantly higher total SAMI scores (p<0.001). The SAMI total score significantly correlated to the PSQI, BDI, and BAI (r=0.65, 0.67, 0.67; all p<0.001). Cronbach's α was 0.95 for the entire scale. The intra-class correlation coefficient between the initial and retest SAMI total score was 0.72 (p<0.001). The SAMI-Chinese demonstrated an area under the receiver operation characteristic curve of 0.771 (SE=0.044; 95% CI: 0.685-0.857; p<0.001) in detecting individuals with poor sleep. A cut-off value of 51 indicated a sensitivity of 0.86 and a specificity of 0.63 in distinguishing between poor and good sleepers.

Conclusions: The SAMI-Chinese demonstrated excellent construct validity, contrast group validity, external validity, internal consistency, and satisfactory test-retest reliability. It also demonstrated satisfactory diagnostic ability for insomnia.