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International Journal of
Environmental Research
and Public Health
Article
Patterns in the Occurrence and Duration of
Musculoskeletal Pain and Interference with Work
among Eldercare Workers—A One-Year Longitudinal
Study with Measurements Every Four Weeks
Charlotte Diana Nørregaard Rasmussen
1,
*, Kristina Karstad
1
, Karen Søgaard
2
,
Reiner Rugulies
1,3,4
, Alex Burdorf
5
and Andreas Holtermann
1,2
1
2
3
4
5
*
National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark
Department of Sports Science and Clinical Biomechanics and Department of Clinical Research,
University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Department of Public Health, University of Copenhagen, Nørregade 10, 1165 København, Denmark
Department of Psychology, University of Copenhagen, Nørregade 10, 1165 København, Denmark
Department of Public Health, Erasmus MC, University Medical Centre, Doctor Molewaterplein 40,
3015 GD Rotterdam, The Netherlands
Correspondence: [email protected]
Received: 5 July 2019; Accepted: 16 August 2019; Published: 20 August 2019
Abstract:
The objective of this study was to examine patterns of musculoskeletal pain episodes over
time. We conducted a one-year follow-up study among 275 eldercare workers with measurements of
musculoskeletal pain (low back pain (LBP) and neck/shoulder pain (NSP)) and pain-related work
interference (PWI) reported via text message every four weeks. We found a constant, high four-weekly
prevalence of LBP and NSP (between 61% and 72%). The distributions of pain episodes for LBP
and NSP were similar with approximately 30% of the episodes being 7 days or less per four weeks.
There was also a high recurrence of pain, with 33% reporting LBP or NSP every four weeks. In addition,
24% had pain at every measurement in both the low back and neck/shoulder regions combined
throughout the year. On days with LBP or NSP, approximately 59% also reported interference
with work, and 18% of the eldercare workers reported that pain interfered with their work all
measurements throughout the year. A high proportion of eldercare workers reported pain every
four weeks throughout the year and the four-weekly prevalence of pain remained high and constant
on a group level. During most days with pain, eldercare workers were hampered in their regular
work activities.
Keywords:
prevalence; low back pain; neck pain; shoulder pain; recurrence; recovery; pain episodes
1. Introduction
The prevalence of, and burden from, musculoskeletal disorders (MSDs) is high throughout the
world with considerable societal costs [1–3]. MSDs are estimated to cause 21% of the total years lived
with disability [4] and are a main cause of absence from work worldwide [1,3]. Even though low back
pain (LBP) and neck/shoulder pain (NSP) are very common health problems, little is known about how
they evolve over time. Thus, whether pain is likely to improve, reoccur, persist, or worsen remains an
important question. More frequent measurements to track the patterns of pain over time will increase
our understanding of MSDs and how they evolve over time [1].
Many previous studies have relied on assessments of MSDs conducted every 3 to 6 months or
even yearly [5,6]. Since most pain episodes may be shorter than 3 months, these studies are not likely to
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www.mdpi.com/journal/ijerph
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capture all fluctuations in MSDs. Text messaging makes it possible to collect data on pain on a monthly,
weekly, daily, or even an hourly basis. Text-messaging-based assessment has shown high compliance
rates unaffected by age, sex, and season and is also very user friendly for several populations [7,8].
When studying pain, it is important to differentiate pain severity from pain interference. Whereas
severity refers to the magnitude of pain, interference refers to pain’s impact on activities [9], including
work [10]. While the 12-month prevalence of pain-related interference with activities has been found
to be 18% among a general working population [11], few studies have investigated the prevalence of
pain-related work interference (PWI) [11]. To our knowledge, no previous studies have investigated
PWI with frequent measurements. Thus, there is an urgent need to increase the understanding of
MSDs and their consequences for workers, including information about PWI and its patterns over time.
To understand how pain changes over time, we studied LBP, NSP, and PWI over a period of one
year through text messages every fourth week among eldercare workers. To our knowledge, this is the
first study to investigate the patterns (episodes of pain) of LBP and NSP and PWI in a longitudinal
study with a 1-year follow-up period with a high frequency of measurements. More specifically,
the aim of this study was to investigate the episodes of LBP, NSP, and PWI in a longitudinal study with
a 1-year follow-up period with a high frequency of measurements and an emphasis on prevalence and
length of episodes.
2. Materials and Methods
The present study was a longitudinal study with a 1-year follow-up period with measurements of
MSDs every four weeks among 275 eldercare workers. For this, we used the prospective workplace
observational study, the Danish Observational Study of Eldercare work and musculoskeletal disorderS
(DOSES), which was designed to examine longitudinal associations between physical and psychosocial
working conditions and the occurrence of MSD and its consequences among eldercare workers [12].
The study received ethical approval from the Danish Data Protection Agency and the Ethics Committee
for the regional capital of Denmark (H-4-2013-028).
2.1. Setting and Participants
The setting for the study was nursing homes in Denmark. We contacted 83 nursing homes by
sending emails. Of those, 20 nursing homes responded with interest in the study and were then
included in the study. The 20 nursing homes were located in Zeeland in the eastern part of Denmark
and had approximately 30–120 residents each. The nursing homes represented both large and small
nursing homes as well as both public and private nursing homes. Eligible participants were employed
more than 15 h a week, were between 18 to 65 years of age, and provided direct care to residents during
at least 25% of their working time. The exclusion criteria to the study were administrative personnel,
kitchen and cleaning personnel and nurses, workers employed on night shifts, and workers who were
long-term sick-listed, pregnant, or not being permanently employed. Written informed consent was
obtained from all participants.
2.2. Data Collection Procedure
The baseline data collection ran from September 2013 to December 2014 with nursing
homes entering the study at different time points during this time period. At baseline,
a structured, self-administered, electronic questionnaire was answered. The questionnaire included
socio-demographic measures, i.e., sex, ethnicity (being born in Denmark or not), health and behavior,
i.e., questions on pain (days), pain intensity in the previous four weeks on a scale from 0–10 (0
=
no pain
and 10
=
worst pain imaginable, a slightly modified Nordic Musculoskeletal Questionnaire [13]),
and smoking. Moreover, body mass index (BMI) (body weight (kg)/(body height (m))
2
) was
objectively measured.
A text message survey (SMS) with measurements of pain was conducted for one year at each
nursing home starting after the baseline data collection (SMS Track
®
system(SMS Track APS, Esbjerg,
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Denmark)) [14]). Every fourth week (on a Monday), the respondents received an automated text
message to their private mobile phone that they were expected to answer by using a text message.
If an answer was not provided, a reminder was sent on Wednesday. If answers were still missing,
we called the participant by phone to get their response.
2.3. Outcomes
Every four weeks, LBP was measured by SMS as days with pain in the lower back. The question
posed was “During the past four weeks, how many days have you had pain in your lower back region?
(Answer from 0–28)”. Likewise, every four weeks, NSP was measured by SMS as days with pain in the
neck/shoulder region. The question posed was “During the past four weeks, how many days have you
had pain in your neck/shoulder region? (Answer from 0–28)”. Finally, every four weeks, pain-related
work interference (PWI) was measured by SMS as days where pain interfered with work. The question
posed was “During the past four weeks, how many days due to your pain in your lower back and/or
pain in neck/shoulders have you had difficulty performing your work (i.e., affected/complicated the
performance of your work tasks)? (Answer from 0–28)” [15]. The question on PWI was only asked if
the participants reported pain in either the lower back or neck/shoulder.
2.4. Definitions of Episodes of Pain
An episode of pain was defined as occurring at least one day with pain per measurement
(four weeks) [2,16,17]. Thus, the four-week prevalence was defined as the proportion of the population
experiencing at least one episode of pain at each time point. The one-year prevalence was defined
as the proportion of the population experiencing at least one pain episode during the one-year
follow-up period. Likewise, a pain-free period consisted of four consecutive weeks without pain [17].
Thus, a period of recovery (recovery) was defined as four weeks (one measurement) without pain
following a period with pain and was interpreted as an improvement in pain. Worsening of pain was
defined as a measurement with pain following a measurement without pain. Repeated pain/repeated
pain free was defined as two or more successive measurements with no change in pain status. Constant
pain/constant pain free was defined as all measurements with pain/no pain.
2.5. Statistics
We used descriptive techniques to present the episodes of LBP, NSP and PWI over time. To avoid
different denominators during the follow-up due to loss during follow-up, the episodes in the presence
of LBP, NSP, and PWI were described among participants with a full dataset with all 14 monthly pain
measurements throughout the year. We conducted a nonresponse analysis to examine whether those
without full answers differed in comparison to those included in the analysis. The episodes of pain
were described using the different categories (constant pain free, repeated pain free, improvement,
worsening pain, repeated pain, and constant pain). All calculations were performed in IBM SPSS
Statistics, version 21 (IBM, Armonk, NY, USA).
3. Results
Initially there were 449 workers from 20 different nursing homes included in the text message
survey. A full dataset with 14 completed measurements consisted of
n
=
275 for LBP,
n
=
273 for NSP,
and
n
=
209 for pain-related work interference (PWI). The discrepancy in the numbers in the datasets
with NSP, LBP, and PWI is due to the possibility of having full answers on either LBP, NSP, or PWI
and missing answers to the others. Only those with full answers on NSP or LBP were included in the
respective analysis. There were no significant differences in age, sex, ethnicity, smoking, body mass
index, and musculoskeletal pain between those included in the text message survey (n
=
449) and
those included in the analysis (n
=
275) (data not shown). The reason for the loss to follow up was
mainly due to participants not answering all text messages throughout the year rather than dropping
out of the study.
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The characteristics of the study population can be seen in Table
1.
The study population consisted
of mostly females (94%). The average age was 47 years, most participants (83%) were born in Denmark,
and 28% reported no LBP or no NSP in the three months before the text message survey. The average
LBP intensity (on a scale from 0 to 10) was 4, and the average NSP intensity was 3 (on a scale from 0
to 10) (Table
1).
Table 1.
Baseline characteristics of 275 eldercare workers in 20 nursing homes in Denmark.
Baseline Characteristic
Mean
(SD)
Age (years)
Sex (female)
Ethnicity (born in Denmark)
Smokers
Body mass index (kg/m
2
)
Low back pain previous 12 weeks
0 days
1–2 days
3–7 days
8–14 days
15–30 days
31–60 days
61–84 days
Neck/shoulder pain previous 12 weeks
0 days
1–2 days
3–7 days
8–14 days
15–30 days
31–60 days
61–84 days
Low back pain intensity (0–10)
Neck/shoulder pain intensity (0–10)
4 (2.3)
3 (2.4)
27 (5.4)
74 (28%)
28 (11%)
53 (20%)
37 (14%)
28 (11%)
21 (8%)
25 (9%)
74 (28%)
32 (12%)
52 (20%)
26 (10%)
36 (14%)
20 (8%)
27 (10%)
47 (10.4)
259 (94%)
228 (83%)
95 (36%)
Numbers
(%)
Data are mean (SD) or numbers (%).
3.1. Duration of Pain (Days per Four Weeks, Days per Year, and Length of Episodes)
The average number of days with LBP per four weeks was 7 (SD: 7.3), and the average number
of days with LBP during the one-year follow-up period was 97 (SD: 100.9). Likewise, the average
number of days with NSP per four weeks was 7 (SD: 7.5), and the average number of days with NSP
during the one-year follow-up was 100 (SD: 105.2). The number of days with PWI per four weeks was
5 (SD: 5.8) and the average number of days with PWI during the one-year follow-up period was 66
(SD: 80.6) (Table
2).
Figure
1
shows the distribution in percentage of length of pain episodes from 1–28 days in all
three pain variables (LBP, NSP, and PWI), averaged from 14 four-weekly measurements. No-pain
episodes (0 days with pain) were registered in 35% of LBP episodes and in 33% of NSP episodes.
The distributions of pain episodes for LBP, NSP, and PWI were similar with approximately 30% of the
episodes being 7 days or less. However, approximately 8% of the pain episodes for LBP and NSP were
28 days during the four-week recall period, compared to approximately 4% for PWI.
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Table 2.
Average duration of low back pain and neck/shoulder pain and pain-related interference with
work (total days per four weeks and total days per year).
Presence of Musculoskeletal Complaints per Person
Mean
Median (Interquartile Range)
Low back pain (total days per year)
97
98 (128)
Low back pain (days per four weeks)
7
7 (9.14)
100
83 (134)
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Neck/shoulder pain
x
Public Health
,
(total days per year)
5 of
Neck/shoulder pain (days per four weeks)
7
6 (10.04)
Pain-related interference
However approximately 8%
66
episodes being 7 days or less.
with work (total days per year)
of the pain episodes
30 (95.00)
and NSP
for LBP
Pain-related interference with work (days per four weeks)
5
2 (6.79)
were 28 days during the four-week recall period, compared to approximately 4% for PWI.
Data are means and medians (interquartile range).
%
%
%
%
%
%
%
%
%
%
%
%
LBP
NSP
PIW
Days
Figure 1.
Distribution in percentage of the study population of the length of pain episodes lasting from
Figure 1.
Distribution in percentage
NSP: neck/shoulder pain;
of the
pain-related interference with work.
1 to 28 days. LBP: low back pain;
of the study population
PWI:
length of pain episodes lasting
from 1 to 28 days. LBP: low back pain; NSP: neck/shoulder pain; PWI: pain-related interference with
3.1.1. Patterns of Pain Episodes
work.
Figures
2–4
show the distribution of categories of pain over one year. When we combined the three
1. Patterns
of pain (i.e., constant pain, repeated pain, and worsening pain), the four-week prevalence of
categories
of Pain Episodes
LBP varied between
show
and
distribution
one-year prevalence of 91%. The four-weekly prevalence of
Figures 2, and 4
61%
the
70% with a
of categories of pain over one year. When we combined
the
NSP varied between
p in (i.e
72% with
pain, repeated p in and
91%. The four-weekly
four-week
of
three categories of
63% and
const nt
a one-year prevalence of
worsening pain) the
prevalence
reporting
LBP v ried between 61% and 70% with one-year prevalence of 91%. The four-weekly
prevalence of
combined LBP and NSP varied between
a
49% and 56% with a one-year prevalence of 79%.
Overall, the prevalence was relatively stable over time, but
prevalence of 91%. The four-weekly
prevalence of NSP v ried between 63% nd 72% with a one-year
on an individual level, the figures also
show great fluctuations in pain
LBP and NSP v ried between 49% and % with a one-year
prevalence of reporting combined
status. For instance, workers were relatively stable pain-free over
time (repeated pain free) or relatively stable in
relatively stable over time, but on an individual
prevalence of 79%. Overall, the prevalence was
pain over time (repeated pain). However, many varied
between the categories “improvement” and
in p in status. For instance, workers were relatively
level the figures lso show gre t fluctuations
“worsening”. For both LBP and NSP, 33% of the eldercare
workers had pain at every measurement throughout the year. In addition, 24% had pain at every
stable p in-free over time (repeated pain free) or relatively stable in pain over time (repeated pain)
measurement in both the low
the categories improvement” and “worsening”.
year.
However, m ny v ried between
back and neck/shoulder combined throughout the
For both LBP and
Figure
2
eldercare
percentages
pain
population divided into categories of
year. In
pain at each
NSP 33% of the
shows the
workers had
of the
at every measurement throughout the
low back
addition,
of the 14 measurement points. Improvement is categorized as a measurement with low back pain
24% had pain at every measurement in both the low back and neck/shoulder combined throughout
the
(an episode of low back pain) followed by a measurement without low back pain (recovery). Worsening
year.
is defined as a measurement without low back pain followed by a measurement with low back pain.
Repeated pain/repeated pain free in low back is defined as two or more successive measurements with
pain/no pain in the lower back.
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%
%
%
%
%
%
%
%
%
%
%
Measure e t
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Co sta t Pai
Free i lo a k
Repeated Pai
Free i lo a k
I pro e e t i
pai i lo a k
Worse i g i
pai i lo a k
Repeated Pai i
lo a k
Figure 2.
Patterns of low back pain episodes over one year.
Figur
P tterns of low b ck p in episodes over one year.
,x
7 of
%
The figure shows the percentages of the population divided into categories of pain at each of
the 1 measurement points. Improvement is categorized as a measurement with pain (an episode of
%
pain) followed by a measurement without pain (recovery). Worsening is defined as a measurement
without pain followed by a measurement with pain Repeated p in/repeated p in free is defined as
%
two or more successive measurements with pain/no pain.
%
%
%
%
%
%
%
%
Measure e t
Co sta t Pai Free i
e k/shoulder
Repeated Pai Free i
e k/shoulder
I pro e e t i pai i
e k/shoulder
Worse i g i pai i
e k/shoulder
Repeated Pai i
e k/shoulder
Co sta t Pai i
e k/shoulder
Figure 3.
Patterns of neck/shoulder pain episodes over one year.
Figure 3.
Patterns of neck/shoulder pain episodes over one year.
The figure shows the percentages of the population divided into categories of pain at each of
the 1 measurement points. Improvement is categorized as a measurement with pain (an episode of
pain) followed by a measurement without pain (recovery). Worsening is defined as a measurement
without pain followed by a measurement with pain Repeated p in/repeated p in free is defined as
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Figure
3
shows the percentages of the population divided into categories of neck/shoulder pain at
each of the 14 measurement points. Improvement is categorized as a measurement with neck/shoulder
pain (an episode of neck/shoulder pain) followed by a measurement without neck/shoulder pain
(recovery). Worsening is defined as a measurement without neck/shoulder pain followed by
a measurement with neck/shoulder pain. Repeated pain/repeated pain free in neck/shoulder is
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defined as two or more successive measurements with pain/no pain in neck/shoulder.
%
%
%
%
%
%
%
%
%
%
%
Measure e t
Figure 4.
Patterns of combined low back pain and neck/shoulder pain episodes over one year.
Co sta t Pai Free i
e k/shoulder a d lo
Repeated Pai Free i
e k/shoulder a d lo
I pro e e t i pai i
e k/shoulder a d lo
Worse i g i pai i
e k/shoulder a d lo
Repeated Pai i
e k/shoulder a d lo
Co sta t Pai i
e k/shoulder a d lo
a k
a k
a k
a k
a k
a k
Figure
4
shows the percentages of the population divided into categories of pain in neck/shoulder
and low back at
shows the percentages of the population divided into categories
as a measurement
The figure
each of the 14 measurement points. Improvement is categorized
of pain at each of
with pain in neck/shoulder and low back (an episode of pain
a measurement with pain
back) followed
the 1 measurement points. Improvement is categorized as
in neck/shoulder and low
(an episode of
by a measurement
a measurement without pain (recovery).
back (recovery). Worsening
measurement
pain) followed by
without pain in neck/shoulder and low
Worsening is defined as a
is defined as
a measurement without pain in neck/shoulder and low back followed by a measurement
defined as
without pain followed by a measurement with pain Repeated p in/repeated p in free is
with pain
in neck/shoulder and low back. Repeated pain/repeated pain free in neck/shoulder and low back is
two or more successive measurements with pain/no pain.
defined as two or more successive measurements with pain/no pain in neck/shoulder and low back.
3.1.2.
with work (total days per four weeks and tot l days per ye r).
Pain-Related Work Interference
Table 2
Average duration of low back pain and neck/shoulder pain and pain-related interference
Figure 4.
Patterns of combined low back pain and neck/shoulder pain episodes over one year.
The distributions of PWI every four weeks were similar for those
Median (Interquartile
experiencing LBP and
Presenc of Musculoskeletal
experiencing
r Person
an
those experiencing NSP. When
Compl ints p
LBP or NSP, approximately 59%
Range)
of participants,
on average, experienced interference
ys per year)
Low b ck p in (total d
with work activities (Figure
5).
Looking at all eldercare workers,
( )
the four-weekly prevalence
(days per four weeks)
44% and 61% with a one-year prevalence of 88%,
of PWI varied between
Low back pain
(9.14)
and 18% of the eldercare
p in (tot
reported that pain interfered with their work every four weeks
workers
l days per year)
Neck/shoulder
( )
throughout the year (Figure
6).
Neck/shoulder pain (days per four weeks)
(10.04)
Pain-related interference with work (tot l d ys per year)
Pain-related interference with work (days per four weeks)
Data are means and medians (interquartile r nge).
(
)
2 (6 9)
Pain-Related Work Interference
The distributions of PWI every four weeks were similar for those experiencing LBP and those
experiencing NSP When experiencing LBP or NSP pproximately % of p rticipants on average
experienced interference with work activities (Figure 5). Looking at all eldercare workers, the
four-weekly prevalence of PWI v ried between 44% nd 61% with a one-year prevalence of %, and
18% of the eldercare workers reported that p in interfered with their work every four weeks
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%
%
%
%
%
%
Figure 5.
Distribution of pain-related work interference among those experiencing NSP and LBP.
Figure 5.
Distribution of pain-related work interference among those experiencing NSP and LBP.
Figure 5.
Distribution of pain-related work interference among those experiencing NSP and LBP.
NSP
NSP
LBP
LBP
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
Figure 6.
Patterns of episodes of pain-related work interference over one year. The figure shows the
Figure 6.
Patterns of episodes of pain-related work interference over one year. The figure shows the
percentages of the population divided into different categories at each of the 14 measurement points.
percentages of the population divided into different interference over of the 14 measurement points.
Figure 6.
Patterns of episodes of pain-related
with
categories at each
interference (PWI) (an episode
Improvement is categorized as a measurement
work
pain-related work
one year. The figure shows the
Improvement is categorized as a measurement with pain-related work 14 measurement points.
percentages of the
by a measurement without PWI (recovery). Worsening
the interference (PWI) (an
with PWI) followed
population divided into different categories at each of
is defined as a measurement
episode with PWI) followed by a a measurement with pain-related work interference (PWI) as
Improvement is categorized as measurement without PWI (recovery). Worsening is defined (an
without PWI followed by a measurement with PWI. Repeated PWI/repeated PWI free is defined as two
measurement PWI) followed by a measurement without PWIPWI. Repeated PWI/repeated PWI free
episode with without PWI followed by a measurement with (recovery). Worsening is defined as
or more successive measurements with PWI/no PWI.
is defined as two or more successive measurements withwith PWI. Repeated PWI/repeated PWI free
measurement without PWI followed by a measurement PWI/no PWI.
4. Discussion
as two or more successive measurements with PWI/no PWI.
is defined
Co sta t free of PWI
Repeated free of PWI
Co sta t PWI
IRepeated e t of PWI
pro e PWI
Worse e geoft PWI
I pro i
of PWI
Repeated g of PWI
Worse i PWI
Co sta t PWI
Repeated PWI
Co sta t PWI
4. Discussion
We found a constant, high four-week prevalence of LBP and NSP. The distribution of pain episodes
4. Discussion
We found
were similar with approximately 30%
LBP
episodes
The distribution of
per
for LBP and NSP
constant, high four-week prevalence of
of the
and NSP.
being 7 days or less
p in
episodes found and
approximately 8% of
prevalence of LBP and NSP.
NSP
being
4 weeks
p in
four weeks. However,
NSP were similar with
the pain episodes for LBP and
The distribution of
long.
We for LBP constant, high four-week approximately 30% of the episodes
were
7 d ys or less
per four weeks.
high
NSP approximately 8% of the p in episodes for LBP and NSP 7 d 4 or less
There was also a
However, were similar with approximately 30% of the episodes beingwereys weeks
episodes for LBP and
recurrence of pain, with 33% of participants reporting LBP or NSP every four
long.
and
w s also a high approximately
and
with
every
episodes for reporting
with
or NSP every
weeks
There
24% reporting combined LBP
pain, of the33% of
four weeks.
LBP
days
NSP were 4 weeks
per four weeks. However, recurrence of 8%
NSP
p in participants
On
and LBP
LBP or NSP,
four weeks ands24% reporting combined LBP and NSP every
with work.
On d ys with LBP or NSP
approximately 59% of
a
participants also reported
with 33% of participants reporting LBP or NSP every
long. There w also high recurrence of pain,
interference
four weeks.
approximately 59% of p rticipants also reported interference with weeks. On d ys with LBP or NSP
four weeks and 24% reporting combined LBP and NSP every four work.
4.1. Prevalence of
59% of p
NSP
approximately
LBP and
rticipants also reported interference with work.
Prevalence of LBP and NSP
Our findings suggest that the prevalence of both LBP and NSP in eldercare workers is very
Prevalence of LBP and
a
that the prevalence of both LBP and NSP
of
eldercare
much higher for
high
high
Our findings suggest
monthly basis. The one-year prevalence
in
LBP was
workers is very
our
when measured on
NSP
when measured
91% compared
sis. The one-year prevalence NSP in
been found to be
for our high
population with
on a monthly b
to
prevalence of both LBP andof LBP was much workers
55% among
Our findings suggest that the
the annual prevalence which has
eldercare higher is very
popul measured on a comp red to the annual prevalence which h s been found higher for among
when tion with 91% monthly b sis. The one-year prevalence of LBP was much to be 55% our
popul tion with 91% comp red to the annual prevalence which h s been found to be 55% among
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eldercare workers [18] and 38% in the general population, respectively [16]. The four-week prevalence
of LBP varied between 61% and 70%, which is much higher than the 31% observed in the general
population [16]. The four-week prevalence of NSP varied between 63% and 72% and the one-year
prevalence was 91%, which is also higher than the mean annual prevalence in eldercare workers
(42%) [18] and in the general working population (27–48%) [19]. Moreover, 33% of the eldercare workers
reported LBP and NSP in all measurements throughout the year. In comparison, a study on LBP in the
general population found that 12% had pain more or less all of the time [20]. Considering both body
regions (NSP and LBP), nearly 60% of the eldercare workers reported pain in at least one region at
all measurements. This aligns with a previous study which showed that when present, the pain is
persistent rather than episodic [21,22]. The observed yearly prevalence measured with the repeated
SMS assessment was high compared to previous findings in the literature. This suggests that either the
repeated measures assessments are overestimating or the traditional single retrospective assessments
are underestimating the prevalence, or a combination of both possibilities may be occurring. Since the
participants were asked to provide baseline information about LBP, NSP, and PWI from the previous
12 weeks, this baseline information was compared with the follow-up 4-weekly measurements to see if
the longitudinal results at follow up were higher than those at baseline. Using the same definition for
prevalence (< 1 day with pain), the prevalence at baseline for the 12-week period was 72% for both LBP
and NSP, which is quite comparable to the monthly prevalence that we found in our study (variation
between 61% and 72%).
In this study, we analyzed pain cases every four weeks. Large variations in the case definition of
pain exist in the literature [2]. For instance, more than 300 case definitions for neck pain have been
identified [23]. Therefore, it is difficult to compare findings because of the use of different questions,
variations in case definitions, and other methodological inconsistencies in previous studies. We used
the definitions described in the Global Prevalence of Low Back Pain and in the review of the Global
burden of neck pain [2,16] yielding findings comparable to those used in large population studies.
4.2. Multimorbidity of LBP and NSP
Previous studies have documented that subjects often report musculoskeletal pain in multiple
body sites [24,25]. The one-year prevalence of LBP and NSP combined in our study was 79% and
the 4-week prevalence of LBP and NSP combined varied between 49% and 56%. This is comparable
to the findings in the study by Haukka et al., who found that 83% of their subjects reported pain in
both the lower back and neck [24]. In addition, 24% had pain every four weeks in the lower back and
neck/shoulder regions combined throughout the year, compared to the 33% reporting either LBP or NSP
all measurements throughout the year. These findings imply that pain episodes are not independent.
4.3. Pain-Related Work Interference
The one-year prevalence of pain-related work interference (PWI) of 88% is considerably higher
than previous findings, where the prevalence of pain-related interference with activities has been found
to be 18% in a general working population [11]. In addition, 18% of the eldercare workers reported PWI
every four weeks throughout the year. Disability due to pain and duration of pain have been found to
be significant predictors for dropout from the eldercare sector 2 years after qualification [26]. We also
found that the distributions of PWI every four weeks were similar for those experiencing LBP or NSP.
It is surprising that in spite of the experience of interference on the majority of days, this has not been
bothersome enough to take sick leave. This is in accordance with the finding in a qualitative study
investigating workers’ strategies towards pain. They found that pain made it more difficult to work,
but job activities were completed nonetheless [27]. Another study found that among older individuals,
health interventions that address chronic musculoskeletal pain may promote subjective health and
quality of life as well as improve mental health [28]. To our knowledge, the present study is the first to
show the magnitude of pain-related interference with work in eldercare workers and warrants further
investigations to find solutions for eldercare workers to be able to remain in their jobs for more years.
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4.4. Episodes of Pain
In our study, we found some variation in the length of episodes with most episodes being one week
or less and only a few being four weeks long. Our study also showed that a substantial proportion of
the eldercare workers had some fluctuations with many recurrent episodes of pain during the one-year
follow-up period. In comparison, another study among healthcare workers observed that 46% of the
subjects with pain varied between being cases or not during a 3-year period [29]. This underlines the
need for replacing previous categorizations of pain as being acute, subacute, or chronic in nature with
more accurate descriptions of time-varying recurrent and prolonged episodes of pain.
4.5. Methodological Issues
Previous studies on the patterns of pain episodes have mostly relied only on a few measurements
taken over time interspersed by long intervals, e.g., years [6]. Such studies may not capture detailed
patterns or fluctuations in pain. In contrast, frequent, repeated measurements of pain facilitate accurate
and precise identification of individual patterns of pain episodes [30] and minimize recall bias [31,32].
The use of measurements of pain every four weeks in the current study is therefore a major strength.
A limitation in this study is the combined NSP question, which did not separate the neck region
from the shoulder region. However, a previous study showed a high concurrence of neck and shoulder
complaints [6]. We only included between 47% and 61% of the original study population in our
analysis, which may have given rise to selection bias. However, baseline measurements of pain
were almost exactly similar to those during repeated follow-up, and we did an analysis to check for
differences in demographic and pain variables between the two populations and found no statistical
differences between them, suggesting that the reported pain was not substantially influenced by
selective participation. Another limitation is the lack of a comparison group to compare the prevalence
of pain in working populations without physically strenuous working conditions.
We followed the eldercare workers every four weeks throughout one year to establish the patterns
of musculoskeletal pain episodes. We chose to use simple descriptive statistics to describe the patterns
of pain episodes in detail. We found that pain was either persistent or episodic rather than presenting
in just one well-defined episode, and therefore, single time-point outcomes are not optimal measures
of musculoskeletal pain. Cohort studies on risk factors for the prevalence of pain should not only pay
attention to new episodes but should also analyze risk factors for constant pain, constant pain-free status,
as well as fluctuations in pain (e.g., improvement and worsening). Also, the use of musculoskeletal
pain as an outcome in intervention studies should be revisited, including considering an increase in the
follow-up period to ensure well-described patterns of pain episodes before and after an intervention
are collected.
5. Conclusions
In summary, LBP and NSP among eldercare workers were characterized by high four-week and
yearly prevalence. Although, at the population level, the prevalence of pain remained constant, the
patterns of pain episodes within individuals demonstrated strong fluctuations. Finally, when studying
pain, it is important to differentiate between pain and functional limitations due to pain. In our study,
we investigated pain-related interference with work. An important finding of our study is that, on most
days with pain, there was also interference with work. More studies on pain-related work interference
(PWI) are needed to establish prognostic factors and to improve diagnosis and treatment when pain
is so severe that it impacts an individual’s ability to work. We also need more studies to evaluate
whether PWI is more predictive of future sick leave and work ability than LBP and NSP alone.
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Author Contributions:
Conceptualization, C.D.N.R, A.H., and A.B.; methodology, C.D.N.R, A.H., K.S., and A.B.;
formal analysis, C.D.N.R.; investigation, A.H., K.K., and R.R.; writing—original draft preparation, C.D.N.R.;
writing—review and editing, C.D.N.R., K.K., A.H., A.B., R.R., and K.S.
Funding:
This study was funded by a grant from the Danish government, through a grant to the FOR-SOSU
program (SATS, 2004) at the National Research Centre for the Working Environment.
Acknowledgments:
We thank the workplaces and workers who contributed to the study.
Conflicts of Interest:
The authors declare no conflict of interest.
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2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).