Patient-specific affect-abdominal pain interactions in endometriosis: an experience sampling method (ESM) study

Figures & data

Table 1. Baseline characteristics.

	Endometriosis (n = 34)	Healthy controls (n = 31)	p-value
Age (Mean [SD])	35.2 [8.7]	30.7 [8.3]	.037
BMI (Mean [SD])	25.7 [5.1]	23.2 [3.3]	.021
Educational level (n, (%))			.924
High school	2 (6)	2 (6)
College/university	32 (94)	29 (94)
Work status (n, (%))			.002
Student	2 (6)	12 (39)
Unemployed	9 (26)	2 (6)
Employed	23 (68)	17 (55)
Relationship status (n, (%))			.831
Single	8 (24)	8 (26)
In relationship	26 (76)	23 (74)
Use of hormones (n, (%))	25 (74)	20 (64)	.035
Regular use of pain medication (n, (%))	26 (74)	1 (3)	<.001
Smoking (n, (%))	6 (18)	1 (3)	.061
Regular use of alcohol (n, (%))	25 (74)	28 (90)	.081
Unplanned childlessness (n, (%))	4 (12)	0 (0)	.049
Traumatic life event* (n, (%))	4 (12)	2 (6)	.460

SD: standard deviation; n: number of patients.

*Traumatic life events had different causes, such as sexual abuse or losing a parent as a child, however, in 3 out of 6 positive answers the cause was not described.

Table 2. Average symptom scores for endometriosis patients vs healthy controls, measured in real-time, several times a day.

Symptom score	Endometriosis (n = 34)	Healthy controls (n = 31)	p-value
Abdominal pain (Mean [SD])	2.79 [2.33]	0.33 [0.96]	<.001
Negative affect:
Feeling dispirited (Mean [SD])	2.01 [2.15]	1.11 [1.82]	<.001
Feeling stressed (Mean [SD])	2.18 [2.35]	1.81 [2.23]	.037
Positive affect:
Feeling cheerful (Mean [SD])	5.23 [1.92]	6.90 [1.50]	<.001
Feeling relaxed (Mean [SD])	5.38 [1.54]	6.41 [2.13]	<.001

SD: standard deviation.

Table 3. Associations between abdominal pain and affect in endometriosis patients and healthy controls.

	Endometriosis (n = 34) B [SE]	Healthy controls (n = 31) B [SE]
Negative affect:
Feeling dispirited (down)	0.15 [0.03], p < .001	.05 [0.02], p = .020
Feeling stressed	0.12 [0.03], p < .001	−0.02 [0.02], p = .412
Positive affect:
Feeling cheerful	−0.14 [0.04], p < .001	−0.04 [0.02], p = .063
Feeling relaxed	−0.06 [0.02], p = .012	0.00 [0.01], p = .805

Regression coefficient (B) and standard error (SE) were tested using linear mixed models with abdominal pain as the dependent variable and the affective symptom as the independent variable, corrected for repeated measures (AR1 covariate structure).

Figure 1. Longitudinal scores for abdominal pain and “feeling dispirited” for two individual patients. The x-axis represents the 70 consecutive assessments: each within a 90-minute timeframe between 7:30 AM and 10:30 PM for each day with a maximum of 10 assessments per day. The heterogeneity between subjects with endometriosis is shown by the different patterns of symptom scores; also indicated by the difference in corresponding regression coefficients for a. 0.12; b. 1.07.

Figure 2. Temporal associations from abdominal pain at time t to the severity of positive and negative affective symptoms at t + 1, and vice versa. The numbers represent Beta coefficients, tested using multi-level linear regression modeling on ESM data. *P < 0.01; **P < 0.001. Bold numbers represent negative predictions. Only significant associations are shown, therefore all lines represent predictions for endometriosis patients. No significant temporal associations were found for healthy controls. Questionnaires are assessed within a 90-minute timeframe. However, as patients were not obligated to fill in every questionnaire during the day, the follow-up questionnaire could be assessed later on the same day.