Does Keeping a Sleep Diary Alter the Perception of Sleep Quality? Testing Measurement Reactivity in Healthy Adults

Measurement reactivity, where the act of measuring a behavior changes that behavior, has been documented across various health outcomes. However, its effects on sleep remain understudied, despite the widespread use of sleep diaries in clinical and research settings. In this randomized experiment, 190 healthy young adults (aged 18-40 years; 63% female) were assigned to complete either a sleep diary (Consensus Sleep Diary) or a physical activity diary (Physical Activity Scale) for seven days. All participants completed the Pittsburgh Sleep Quality Index (PSQI) and the International Physical Activity Questionnaire (IPAQ) before and after the diary period. Daily diary completion rates were high (97.3%). Linear mixed-effects models revealed no significant main effects of time (pre vs. post) or condition (sleep vs. physical activity diary), and no significant interaction between time and condition for either PSQI or IPAQ scores. These results suggest stability in sleep quality and physical activity measures, with no evidence of measurement reactivity. An exploratory analysis comparing "good" and "poor" sleepers (based on baseline PSQI scores) found a significant effect of sleep quality group and a time × group interaction on PSQI scores. In this adequately powered short-term study of young adults, we found no evidence of measurement reactivity to daily sleep diaries. These findings suggest that in healthy individuals, completing a week of sleep diaries is unlikely to impact PSQI scores substantially. We discuss our results in terms of the direct controllability of sleep quality, which might make it less susceptible to measurement reactivity relative to other health outcomes.