Abstract
PURPOSE: Healthy, young individuals are known to exhibit circadian variation in urinary functions. However, the effects of chronic circadian disturbance on voiding functions are largely unknown. The present work compared the effects of rotational shifts on the micturition patterns of female nurses to that in female nurses with routine daytime shifts. METHODS: A total of 19 nurses without lower urinary tract symptoms who worked rotational shifts for an average duration of 2 years were recruited. A voiding diary was kept for 9 consecutive days, and the overactive bladder symptom score (OABSS) questionnaire was completed three times, starting 3 days before their night duties until 3 days after completion of their night duties. For comparison, seven nurses with regular shifts completed a 3-day voiding diary and the OABSS questionnaire. RESULTS: Female nurses working rotational shifts had lower overall urine production and had decreased urination frequency and nocturia than female nurses working regular shifts, even when the nurses who worked rotational shifts had a regular night's sleep for at least 7 days. Upon reinitiation of night duty, overall urine production increased significantly, with no significant changes in urgency and frequency. When these nurses returned to daytime duty, the volume of urine decreased but nocturnal urine production remained high, and the incidence of nocturia also increased significantly. However, the effects on OABSS score were not significant under the study design used. CONCLUSIONS: Long-term rotational shifts resulted in adaptive changes such as decreased urine production and frequency in healthy, young female nurses. In addition, their micturition patterns were significantly affected by abrupt changes in their work schedules. Although working in shifts did not increase urgency or frequency of urination in healthy, young female nurses working rotational shifts for an average 2 years, large-scale studies are needed to systematically analyze the influence of shift work timings on micturition in humans.