Abstract
Background: Sleep quality is a complex construct to evaluate empirically, and yet the Pittsburg Sleep Quality Index (PSQI) is commonly used in studies as their only measure of sleep quality. Furthermore, the PSQI may not be the best sleep quality measure for older adults post coronary artery bypass graft (CABG), due to its reliance on the cognitive capacity to reflect on the past month. Purpose: The present study was conducted to compare the PSQI's predictive validity as a subjective measure of sleep quality with an objective sleep quality (as measured by actigraphy). Methods: 80 male participants aged 45-65years-who underwent coronary artery bypass graft CABG since 6 weeks - were randomized to two groups: aerobic group (AG), and combined aerobic and resistance group (ARG). Training lasted ten consecutive weeks with 30 uninterrupted sessions. The actigraph together with Pittsburg sleep quality index (PSQI) were used in sleep quality assessment. The actigraph (Actiwatch Minimitter Company, Incorporated (INC) - Sunriver, OR, USA) was placed on the non-dominant wrist and activities were monitored continuously while being recorded at one minute intervals. The participants kept the device for a period of 96 hours, filled PSQI, and did 6MWT before the first and last training sessions. Pearson’s correlation was used to assess the relationship between the data obtained from these 2 assessment methods. Results: Our results suggest perceived sleep quality is quite different from objective reality, at least for this group. Previous studies have shown the PSQI to be a valuable tool for assessing subjective sleep quality; however, our findings indicate for middle aged adults who did CABG the PSQI should not be used as a substitute for actigraphy, or vice versa. Conclusion: The best practice is to include both subjective and objective measures when examining sleep quality in older adults (i.e., the PSQI,and actigraphy).

Key words: Sleep quality, exercise, CABG, actigraphy, PSQI.