Improved Sleep Quality and Work Performance Among Shift Workers Consuming a “Foods with Function Claims” Containing Asparagus Extract

Abstract

The purpose of this study was to examine whether Foods with Function Claims (FFC) containing asparagus extract effectively improved sleep quality and work performance in shift workers. An intervention study with a before-and-after intervention design was conducted on nurses engaged in two-shift work at a hospital, ingesting a FFC containing asparagus extract. The evaluation period lasted at least two weeks, including three nights shifts during the period. Before and after ingestion, Pittsburgh Sleep Questionnaire Index (PSQI), Utrecht Work Engagement Scale (UWES), Sleep quality (VAS-rated), impaired work functioning, and psychiatric symptoms were evaluated. A diary record, wearing of an activity meter, and a Psychomotor vigilance test were also performed at baseline and after intervention. Data were analyzed by the paired t-test or the Wilcoxon rank sum test. Among 34 participants, 33 completed the study. The results of the primary outcome measures showed significant improvements in PSQI and Sleep Quality in the night of the day after a night shift (PSQI total score: base line 7.41/ post intervention 6.03: P < 0.001; sleep quality: base line 4.48/post intervention 6.00: P < 0.001). The results of the secondary outcome measures showed significant improvements in UWES and feeling of fatigue. There was also trend of improvement in sleep efficiency and the reaction time. There was no significant improvement in impaired work functioning. This study showed that regular consumption of an FFC containing asparagus extract could improve sleep quality, feeling of fatigue, and work engagement among shift workers. Some caution, however, is needed when interpreting the results because of the before-and-after intervention design without a control group.