Effects of illness perception on negative emotions and fatigue in chronic rheumatic diseases: Rumination as a possible mediator

Table 1 Sociodemographic and disease characteristics of patients with chronic rheumatic diseases

	RA	SLE	t-test or chi-squared test	P value
Overall n (%)	33 (62.3)	20 (37.7)
Gender
Male	7 (21.2)	2 (10.0)	χ2 = 1.110, 1 df	0.292
Female	26 (78.8)	18 (90.0)
mean age (SD)	61.12 ± 15.00	37.10 ± 13.52	t = 5.860	< 0.001
Ethnicity
Chinese	26 (78.8)	11 (55.0)	χ2 = 5.915	0.116
Malay	2 (6.1)	6 (30.0)
Indian	4 (12.1)	2 (10.0)
Others	1 (3.0)	1 (5.0)
Education
Primary school	14 (43.8)	3 (15.0)	χ2 = 6.150	0.046
Secondary school	10 (31.3)	6 (30.0)
Tertiary and university	8 (25.0)	11 (55.0)
Marital status
Married	24 (72.7)	10 (50.0)	χ2 = 0.140	0.085
Single	9 (27.3)	10 (50.0)
Employment
Employed	19 (57.6)	16 (80.0)	χ2 = 7.158	0.007
Unemployed	14 (42.4)	4 (20.0)
Financial status
Poor	3 (9.1)	1 (5.0)	χ2 = 1.620	0.445
Average	26 (78.8)	14 (70.0)
Good	4 (12.1)	5 (25.0)
Duration of illness	4.24 ± 4.30	4.87 ± 5.51	t = 0.454	0.343
Receiving long-term medication
Yes	31 (93.9)	19 (95.0)	χ2 = 0.026	0.871
No	2 (6.1)	1 (5.0)
Hospitalisation in the previous year as a result of RA or SLE
Yes	7 (21.2)	8 (40.0)	χ2 = 2.166	0.141
No	26 (78.8)	12 (60.0)

Discrete variables (gender) were compared using the chi-squared test and df and χ² are presented in the table. Continuous variables were compared with independent sample t test and t values are presented. SLE: Systemic lupus erythematosus; RA: Rheumatoid arthritis.

Table 2 Components of illness perception, rumination and negative emotions in patients with chronic rheumatic diseases

	RA	SLE	t	P value
Various components of illness perception
Perceived identity of illness	4.24 ± 2.24	4.40 ± 2.96	-0.220	0.827
Perceived chronicity of illness	17.21 ± 4.25	20.50 ± 4.05	-2.780	0.008
Perceived cyclical nature of illness	12.18 ± 3.25	12.35 ± 3.17	-0.184	0.855
Perceived consequences of illness	17.58 ± 4.14	19.15 ± 4.20	-1.335	0.188
Perceived illness coherence	15.30 ± 3.82	15.30 ± 3.10	0.003	0.998
Rumination	832.52 ± 470.09	1181.25 ± 355.13	-2.856	0.006
Global fatigue index	18.31 ± 9.71	23.02 ± 8.62	-1.781	0.081
Total DASS score	20.61 ± 19.81	32.20 ± 27.35	-1.785	0.080
Depression score	6.48 ± 7.50	8.30 ± 8.32	-0.820	0.416
Anxiety score	5.94 ± 5.93	10.40 ± 9.64	-2.092	0.041
Stress score	8.18 ± 8.51	13.50 ± 10.89	-1.983	0.053

SLE: Systemic lupus erythematosus; RA: Rheumatoid arthritis; DASS: Depression, anxiety and stress scale-21.

Table 3 Correlations among various components of illness perception, rumination, fatigue, and negative emotions among patients with chronic rheumatic diseases

Illness perception	Fatigue		Negative emotions		Rumination
	r	P value	r	P value	r	P value
Identity of illness	0.482	< 0.001	0.507	< 0.001	0.422	0.002
Chronicity of illness	0.264	0.046	0.296	0.031	0.24	0.043
Cyclical nature of illness	0.477	< 0.001	0.48	< 0.001	0.416	0.002
Consequences of illness	0.451	0.001	0.489	< 0.001	0.443	0.001
Coherence of illness	-0.265	0.045	-0.257	0.063	-0.21	0.048
Rumination	0.703	< 0.001	0.626	< 0.001

Table 4 Mediation effect of rumination on the relationship between illness perception and fatigue/negative emotions using the sobel test

	Fatigue		Negative emotions
	Sobel z value	P value	Sobel z value	P value
Identity of illness	2.96	0.003	2.64	0.008
Chronicity of illness	1.71	0.086	1.67	0.096
Cyclical nature of illness	2.92	0.003	2.61	0.009
Consequences of illness	3.10	0.002	2.74	0.006
Coherence of illness	-1.50	0.135	-1.46	0.143

Table 5 Summary of bootstrap analysis showing the indirect effects of rumination on the three components of illness perception and fatigue and negative emotions

Independent variables	Mediator	Dependent variable	a path coefficient	b path coefficient	c path coefficient	c’ path coefficient	Bootstrap biased correct indirect effects
							Point estimate	Lower	Upper
Identity of illness	Rumination	Fatigue	0.422b	0.703b	0.482b	0.226a	0.457a	0.081	1.116
Cyclical nature of illness	Rumination	Fatigue	0.416b	0.703b	0.477b	0.223a	0.288	-0.097	0.984
Consequences of illness	Rumination	Fatigue	0.443b	0.703b	0.451b	0.174a	0.056	-0.251	0.465
Identity of illness	Rumination	Negative emotions	0.422b	0.626b	0.507b	0.295a	0.714a	0.102	2.029
Cyclical nature of illness	Rumination	Negative emotions	0.416b	0.626b	0.480b	0.266a	0.450	-0.134	1.826
Consequences of illness	Rumination	Negative emotions	0.443b	0.626b	0.489b	0.264a	0.088	-0.370	0.836

^aP < 0.05.

^bP < 0.01.