Evaluation of latent links between irritable bowel syndrome and sleep quality

Table 1 Clinical subtypes, physical and life-habit variables of irritable bowel syndrome patients

	Item categories	Patients (%)
IBS subtype	M-IBS	29.6
	D-IBS	33.8
	C-IBS	36.6
Age (yr)	≤ 50	78.9
	> 50	21.1
Sex	Male	22.5
	Female	77.5
BMI (kg/m2)	≤ 25	76.1
	> 25	23.9
Smoking	No	74.6
	Yes	25.4
Alcohol consumption	Non-/occasional drinkers	82.4
	Light drinkers (< 30 g ethanol/d)	17.6
Coffee consumption	< 2 cups/d	55.6
	≥ 2 cups/d	44.4
Physical activity	No	66.2
	Yes	33.8
Water consumption	< 1.5 L/d	61.3
	≥ 1.5 L/d	38.7

IBS: Irritable bowel syndrome; BMI: Body mass index.

Table 2 Distribution of responses to the items in the irritable bowel syndrome Symptom Severity Score across categories (low, medium and high)

IBS-SSS items	Category (score interval)	Patients (%)
Pain severity	Low: ≤ 40	31.0
	Medium: 40-70	43.7
	High: > 70	25.4
Pain frequency	Low: ≤ 20	19.7
	Medium: 20-70	33.8
	High: > 70	46.5
Distension	Low: ≤ 40	30.3
	Medium: 40-70	28.2
	High: > 70	41.5
Dissatisfaction with defecatory function	Low: ≤ 40	12.7
	Medium: 40-70	26.8
	High: > 70	60.6
Interference with daily life style	Low: ≤ 40	28.9
	Medium: 40-70	32.4
	High: > 70	38.7

IBS-SSS: Irritable bowel syndrome Symptom Severity Score.

Table 3 Distribution of responses to Pittsburgh Sleep Quality Index items

PSQI items	Item scores	Patients (%)
Subjective sleep quality	0	14.1
	1	62.7
	2	20.4
	3	2.8
Sleep latency	0	52.8
	1	28.2
	2	14.1
	3	4.9
Sleep duration	0	43.7
	1	35.9
	2	14.8
	3	5.6
Habitual sleep efficiency	0	54.9
	1	33.8
	2	7.7
	3	3.5
Sleep disturbances	0	8.5
	1	81.0
	2	9.9
	3	0.7
Use of sleeping medication	0	81.0
	1	3.5
	2	2.1
	3	13.4
Daytime dysfunction	0	31.0
	1	50.7
	2	13.4
	3	4.9

PSQI: Pittsburgh Sleep Quality Index.

Table 4 Contingency table for the global irritable bowel syndrome Symptom Severity Score and global Pittsburgh Sleep Quality Index score

	Global PSQI score
	Good	Poor
Global IBS-SSS
Mild	7	3
Moderate	44	25
Severe	31	32

IBS-SSS: Irritable bowel syndrome Symptom Severity Score; PSQI: Pittsburgh Sleep Quality Index.

Table 5 For each patient, feature regression coefficients (posterior means) and 95% confidence interval for the latent severities of both irritable bowel syndrome and sleep disturbances are shown

Patient features	Categories	IBS latent severity, coef (95% CI)	Sleep disturbances latent severity, coef (95% CI)
IBS subtype	Mixed	0	0
	Diarrhoea	-0.10 (-0.45 to 0.24)	0.02 (-0.42 to 0.46)
	Constipation	0.32 (-0.05 to 0.69)	0.16 (-0.30 to 0.65)
Age (yr)	≤ 50	0	0
	> 50	-0.38 (-0.75 to -0.02)1	0.49 (0.02 to 0.96)1
Sex	Male	0	0
	Female	0.10 (-0.24 to 0.46)	-0.53 (-0.95 to -0.07)1
BMI (kg/m2)	≤ 25	0	0
	> 25	0.04 (-0.32 to 0.38)	0.09 (-0.33 to 0.52)
Smoking	No	0	0
	Yes	0.07 (-0.27 to 0.41)	-0.04 (0.45 to 0.38)
Alcohol consumption	Non-/occasional drinkers	0	0
	Light drinkers	-0.22 (-0.60 to 0.16)	-0.60 (-1.08 to -0.12)1
Coffee consumption	< 2 cups/d	0	0
	≥ 2 cups/d	-0.31 (-0.60 to -0.01)1	-0.08 (-0.44 to 0.26)
Physical activity	No	0	0
	Yes	-0.18 (-0.48 to 0.11)	-0.29 (-0.68 to 0.08)
Water consumption	< 1.5 L/d	0	0
	≥ 1.5 L/d	0.27 (-0.03 to 0.56)	0.07 (-0.29 to 0.42)

¹Significant differences between covariables. IBS: Irritable bowel syndrome. CI: Confidence interval; BMI: Body mass index.