Patients were enrolled between June 2012 and August 2013 at the Osaka City University hospital. Adult IBD outpatients were eligible only if they met the inclusion criteria for this study. Only patients who were ≥18 years of age and treated with medicine at our hospital were included in the present study. The exclusion criteria included: (1) shift workers; (2) pregnancy and nursing; (3) severe malignant disease; (4) severe sleep disorders such as obstructive sleep apnea syndrome that required nasal continuous positive airway pressure; and (5) home parenteral nutrition or infusion therapy. Patients with a stoma were also excluded because standard symptom-based measures of disease activity are not applicable to these patients. This study was approved by the Osaka City University Ethics Committee and informed consent was obtained from all participants.
Questionnaire and data collection
All participants were asked to complete a self-administered questionnaire aimed at evaluating alcohol drinking habits, smoking status, caffeine intake, sleep disturbances, and HR-QOL. Sleep disturbances were assessed by a Japanese version of the Pittsburg sleep quality index (PSQI) while HR-QOL was evaluated according to a Japanese version of the 8-item short-form health survey (SF-8). The demographics and information including age, sex, height, body weight, types of IBD, disease duration, disease activity, presence or absence of prior surgery for IBD, symptoms, current medications, and comorbidities were collected from medical charts. Body mass index (BMI) was calculated as the ratio between body weight and the squared height (kg/m2).
PSQI and definition of sleep disturbances
The PSQI consisted of 17 individual items that generated the seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction. Each component score ranged from 0 to 3, and the sum of all the component scores provided the total score, with high scores indicating poor sleep (Buysse et al. 1989). In the Japanese version, a PSQI >5.5 has a sensitivity of 80.0–85.7 % for several different patient groups and a specificity of 86.6 % for control subjects (Doi et al. 2000). Patients with a total PSQI >5.5 were classified as patients with sleep disturbances (Doi et al. 2000).
The SF-8 was developed to estimate HR-QOL based on the scores from eight domains and two summaries: physical functioning (PF), role physical (RF), bodily pain (BP), general health perception (GH), vitality (VT), social functioning (SF), role emotional (RE), mental health (MH), physical component summary (PCS), and mental component summary (MCS) (McHorney et al. 1993; Ware et al. 1994). PF, RF, and BP scales show the strongest correlation with the physical component. The mental component correlates show the strongest correlation with the RE and MH scales. Three of the scales (GH, VT, and SF) have significant correlations with both components. Importantly, SF-8 scores show a strong correlation with SF-36 scores. Scores for PCS and MCS are calculated according to the manual of the Japanese version of the SF-8. A score of ~50 is the average for the Japanese adult population in eight domains and two summaries, while a lower score indicates a poorer HR-QOL (Fukuhara and Suzukamo 2004).
We evaluated the disease activity using the Harvey-Bradshaw index (HBI) for CD (Harvey and Bradshaw 1980; Vermeire et al. 2010) and the partial Mayo score (pMayo) for UC (Schroeder et al. 1987; Leong et al. 2014; Lewis et al. 2008). HBI was composed of 5 parameters including general well-being (ranged from 0 to 4), abdominal pain (ranged from 0 to 3), number of liquid stools per day (1 per occurrence), abdominal mass (ranged from 0 to 3), and complications (1 per item such as arthralgia, uveitis, erythema nodosum, aphthous ulcer, pyoderma gangrenosum, anal fissure, new fistula, and abscess). The higher scores indicated more severe disease activity and an HBI greater than 5 was used to define an active disease for cases of CD (Vermeire et al. 2010). The pMayo entailed information on diarrhea, rectal bleeding, and a physician’s global assessment that ranged from 0 to 3. Higher pMayo scores represented greater UC disease activity and pMayo scores greater than 3 were used to defined an active disease for UC (Minami et al. 2015).
Assessment of disease flare
A retrospective cohort study was performed to examine the association between disease flares and sleep disturbances. We investigated the risk factors for disease flares in the year preceding enrolment. The information about disease flare within 1 year from enrollment was assessed by using medical charts. The disease flare was defined as a case with either: (1) more than 2-point increase in disease activity score, (2) cases requiring dose escalation of immunosuppressive therapy such as tacrolimus hydrate, azathioprine, and mercaptopurine, (3) initiation or addition of new drugs such as anti-TNFα biologic agents, (4) treatment with IBD-related surgery, or (5) hospitalization.
Values are presented as mean and standard deviation (SD), frequency (%), or odds ratio (OR) with 95 % confidence intervals (CI). Comparisons between the two groups were performed using the Chi-squared test or the student’s t test. A multiple logistic regression model was created to assess independent associations between risk factors and disease flare within 1 year from enrollment. Data were considered statistically significant at P < 0.05. The statistical analysis was performed with SPSS (21.0 J SPSS Japan, Tokyo, Japan).