Predictors of chronic pain
are reported in Table I. The mean pain intensity for
responders with pain at T1 was 4.7 (SD 2.0) and the
mean pain sensitivity (PSQ) was 3.9 (SD 1.5) among
all respondents at T1. The prevalence of NP was
54.5%. Of all the respondents at T1, the prevalence of
LP was 18.0%, RP-Medium 20.7%, RP-Heavy 4.9%,
and WSP 1.9%.
Table I also reports physical and psychological
comorbidities. The most common comorbidities at
T1 were as follows: CVDs (25.3%), RA/OA (21.8%),
and CNS disorders (20.4%).
Predicting pain intensity at T1
The univariable and multivariable analyses are pre-
sented in Table II. Univariable analyses showed that
all the examined variables at T0, except citizenship,
had p-values below 0.05 in their associations with pain
intensity at T1. In the multivariable analysis, without
any pain characteristics at T0 included, female sex,
immigrant, traumatic injuries, RA/OA, CVDs, pulmo-
nary, GI, CNS and metabolic disorders, and depression
at T0 were positive predictors of pain intensity at T1,
whereas age and higher education were protective
predictors (Table II; multivariable model 1).
When the 3 investigated characteristics of pain
at T0 were introduced as predictors, they were all
187
positive predictors (Table II; multivariable model 2).
Female sex, traumatic injuries, CVDs, and pulmonary
disorders remained as positive predictors. Only high
education remained as a protective predictor (Table II;
multivariable model 2).
Predicting spread of pain at T1
The univariable and multivariable analyses are presen-
ted in Table III. Univariable analysis showed that all the
examined variables at T0, except for citizenship, were
clearly associated with spread of pain at T1 (p < 0.001).
Multivariate analysis, without any pain characteristics
at T0, showed that being female, immigrant, all studied
comorbidities except for pulmonary and urogenital
disorders, and tumours/cancer were positive significant
predictors of spread of pain at T1, whereas higher edu-
cation and unemployment were significant protective
predictors (Table III; multivariable model 1).
When the 3 pain characteristics at T0 were intro-
duced as predictors, the following variables remained
as positive predictors: female, traumatic injuries, RA/
OA, CNS, and GI disorders, whereas higher education
and unemployment disappeared as predictors (Table
III; model 2). In addition, all pain characteristics at T0
were positive predictors for spread of pain at T1 (Table
III; multivariable model 2).
Table II. Baseline predictors (T0) for pain intensity at 2-year follow-up (T1)
Multivariable 1
Multivariable 2
(N = 4,473; 15.7% missing data)* (N = 3,823; 28.1% missing data)*
Univariable
Baseline predictors
Estimate (B) 95% CI
Estimate (B) 95% CI
Pain spreading a
Pain sensitivity
Age, years 0.51 0.48, 0.54 < 0.001 0.52
0.27
0.10 0.47, 0.56 < 0.001
0.24, 0.31 < 0.001
0.05, 0.15 < 0.001 Marital status (married/other b ) 0.35 0.24, 0.46 < 0.001 0.34
0.14 0.07, 0.20 < 0.001 0.08
–0.35 –0.41, –0.28 < 0.001 –0.29
0.35 0.25, 0.46 < 0.001 0.59
p-value Estimate (B) 95% CI
p-value
0.43 0.40, 0.47 < 0.001
–
–
0.001 0.13
0.08
–0.03 0.06, 0.20
0.04, 0.11
–0.11, 0.05 < 0.001
< 0.001
0.501
0.23, 0.46 < 0.001 0.14 0.03, 0.26 0.019
0.00, 0.16 0.052 0.06 –0.02, 0.13 0.163
–0.37, –0.21 < 0.001 –0.13 –0.22, –0.05 0.001
0.03 –0.11, 0.16 0.712 0.02 –0.12, 0.16 0.765
0.41, 0.77 < 0.001 0.31 0.12, 0.51 0.002 0.05 –0.16, 0.28 0.739
0.38
–0.18 –0.03, 0.78
0.070
–0.22, –0.13 < 0.001 –
–0.03 –
–0.08, 0.03 –
0.322 –
–0.04 –
–0.09, 0.02 –
0.166
0.65 0.50, 0.79 < 0.001 0.45 0.30, 0.60 < 0.001 0.25 0.10, 0.39 0.001
Cardiovascular disorders (yes/no b ) 0.69 0.58, 0.81 < 0.001 0.45 0.32, 0.57 < 0.001 0.11 –0.01, 0.24 0.077
0.47 0.35, 0.59 < 0.001 0.31 0.17, 0.44 < 0.001 0.21 0.07, 0.35 0.002
Pulmonary disorders (yes/no ) 0.65 0.49, 0.81 < 0.001 0.32 0.15, 0.49 < 0.001 0.22 0.05, 0.38 0.011
Disorders of the CNS (yes/no b ) 0.55 0.42, 0.67 < 0.001 0.29 0.15, 0.42 < 0.001 0.12 –0.02, 0.25 0.091
0.40 0.28, 0.52 < 0.001 0.17 0.04, 0.30 0.012 –0.02 –0.15, 0.10 0.716
Skin diseases (yes/no b ) 0.58 0.36, 0.80 < 0.001 0.23 –0.01, 0.47 0.061 0.05 –0.19, 0.28 0.696
0.25 0.10, 0.41 0.001 0.03 –0.13, 0.19 0.694 0.01 –0.15, 0.17 0.891
0.28 0.01, 0.54 0.041 0.03 –0.27, 0.32 0.851 0.14 –0.17, 0.45 0.364
0.55 0.39, 0.70 < 0.001 0.23 0.07, 0.40 0.006 0.03 –0.13, 0.19 0.297
0.57 0.43, 0.70 < 0.001 0.31 0.16, 0.45 < 0.001 0.13 –0.02, 0.27 0.082
0.46 0.33, 0.59 < 0.001 – –
Pain intensity
Sex (female/male b )
Educational level (university/other b )
Employment (unemployed/employed b )
Country of birth (abroad/Sweden b )
Citizenship (other/Sweden b )
Household income, Euros per year
Traumatic injuries (yes/no b )
Rheumatoid arthritis-osteoarthritis (yes/no b )
b
Gastrointestinal disorders (yes/no b )
Urogenital disorders (yes/no b )
Tumours/cancer (yes/no b )
Metabolic disorders (yes/no b )
b
Depression (yes/no )
Anxiety (yes/no b )
p-value
–
–
–
–0.13
–
–
–
–0.21, –0.06
–
–
–
–
–
*N = number of complete cases included in the models out of a total of 5,305 valid responses for pain intensity. Pain intensity was measured only in pain population.
a
Baseline spread of pain was entered to the models as covariate with 5 levels 0 = no pain, 1 = local pain, 2 = Regional Pain-Medium, 3 = Regional Pain-Heavy, and
4 = widespread pain. b Reference category.
CNS: central nervous system; B: unstandardized regression coefficient; CI: Wald confidence interval; multivariable 1: all baseline variables together in 1 model
without baseline pain dimensions; Multivariable 2: all baseline variables from multivariable model 1, including baseline pain dimensions. Significant differences in bold.
J Rehabil Med 51, 2019