TABLE 1.

Characteristics of the retrieved studies

Author (reference), year	Study design	Participants	Measures/variables	Main results
Julian et al (51), 2008	Longitudinal/NARCOMS	n=8867 (W: 74%) Age: 48±9 years PDDS: 3 Disease duration: 18±11 years	0–5 Pain Performance Scale Interference with employment loss and initiation over six months Employment status	There was a significant difference between employed and unemployed patients with regard to pain; however, pain was not significantly predictive of employment loss (OR=1; P=0.9) or employment initiation (OR=1; P=0.8).
Glad et al (55), 2010	Cohort	n=188 (W: 64%) Age: 54±9 years Disease duration: 22±3 years; EDSS: 5±2	Impact of nonmotor symptoms on employment Chronic pain: present or not Employment status (full-or part-time) Type of occupation	Prevalence of pain was 54%. Pain was not associated with unemployment. The estimated OR for chronic pain as a prognostic factor for unemployment was 4 (P=0.1).
Glad et al (54), 2011	Cohort	n=188 (W: 64%) Age: 54±9 years Duration: 22±3 years; EDSS: 5±2	Clinical examination/interview/questionnaires Pain: present or not Employment status and type of occupation	63% of the patients reported pain. 32% of the cohort was employed. There was an increasing proportion of patients not being employed in the presence of pain (OR 2 [95% CI 1–6]; P=0.3).
Douglas et al (52), 2008	Cross-sectional	n=219 (W: 82%) Age: 51±12 years (range 24–82) Median MS duration: 9 years (range 0.5–60)	Mailed questionnaire/structured interview Pain intensity (NRS), pain quality (MPQ), location, duration and management. 0–5 GNDS scale to measure disability in domains due to pain. Hours of paid employment per week	67% reported pain. 66% were not in paid work. Comparisons between participants with and without pain did not reveal any significant associations between the presence of pain and employment status (rate of employment in pain group: 31%, and in pain-free group: 37%; P=0.5.
Ehde et al (36), 2003	Cross-sectional	n=442 (W: 75%) Age: 50±11 years Duration of MS: 13±10 years	Mail survey questionnaires 0–10 NRS: Average pain intensity and pain interference on activity and work/SF-36 Employment status: Employed or not	44% reported pain. 39% were employed. Rate of employment in pain group: 35%, pain-free group: 42%, P=0.1; no significant difference in employment rate.
Ehde et al (38), 2006	Cross-sectional	n=180 (W: 78%) Age: 50±11 years (pain); 50±12 years (no pain) Duration of MS: 13±10 years	Postal survey / 0–10 NRS: pain/SF-36 Brief Pain Inventory Scale: Pain interference with normal work. CIQ: lack of handicap, and productive activity/employment status	Pain prevalence was 66%. Persons with pain were less employed (employment rate: with pain 25%, without pain 50%, P<0.001). Productive activity was significantly different between the two groups (pain group reported less productivity).
Forbes et al (59), 2006	Cross-sectional	n=929 (W: 69%) Age: 48±11 years (range 17–81) Duration of MS: 16±10 years	Postal survey using a piloted questionnaire. Presence of pain/0–5 ordinal scales to measure severity of pain and problem with employment due to MS symptoms Multiple Sclerosis Impact Scale-29: disease impact/SF-36	Pain affected 73% of the sample. Mean bodily pain: 56±26 (0–100). 28% of the sample was employed. Those with less pain (68 on BPS) had no problem with employment, while those with more pain (56 on BPS) reported severe problems with employment.
Michalski et al (50), 2011	Cross-sectional	n=38 (W: 82%) Age: 42±11 years Disease duration: 9±7 years (range 1–26); EDSS: 4±2	Pain intensity (NRS), quality (PSS), pain-related behavior (FSR), health care utilization and bodily complaints (GBB-24) Employment status/number of days off work	82% reported pain. Patients with pain had increased days off work, although this was not statistically significant (patients with pain: 70 days off per year; pain-free patients: three days)
Piwko et al (53), 2007	Cross-sectional	n=297 (W: 77%) Age: 49±11 years	Standardized questionnaires/telephone interview Box Score-11 scale/Health Utilities Index Mark 3: pain Pain type and severity and treatment Employment status: employed or not	Pain prevalence was 71%. 13% of patients with pain were employed and 80% were unemployed. In patients without pain these rates were 23% and 70%, respectively. There was no significant difference (P=0.1) in employment status between participants with pain and without pain.
Warnell (58), 1991	Cross-sectional	n=364 (W: 68%) Age: mean 43 years (range 19–74)	An author-developed questionnaire. Pain prevalence, intensity, frequency, quality and location. 0–10 VAS: pain intensity/QOL, employment status	64% reported pain. Pain compromised the ability to work in 49% of subjects. Patients in two groups were similar with regard to employment rate (56% versus 57%).

BPS Bodily pain subscale of the Short Form Health Survey (SF-36); CIQ Community Integration Questionnaire; EDSS Expanded Disability Status Scale; FSR Questionnaire on Pain Regulation; GBB-24 Giessen-subjective complaints list; GNDS Guy’s Neurological Disability Scale; MPQ McGill Pain Questionnaire; MS Multiple sclerosis; NARCOMS North American Research Committee on Multiple Sclerosis; NRS Numeric rating scale; PDDS Patient Determined Disease Steps; PSS Pain Sensation Scale; QOL Quality of life; VAS Visual analogue scale; W Women