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criteria, the median methodological quality of all 16
studies was 12/15 (range 8–15). There were 12 studies
of high quality, 3 of moderate quality and one of low
quality. The intraclass correlation coefficient for the
inter-rater agreement between the 2 reviewers was
0.879 (95% CI 0.667–0.956).
Study characteristics
The 16 included studies were published between 1993
and 2017. The characteristics of the included studies
are shown in Table III. Studies consisted of 1 prospec-
tive, 1 retrospective cohort, and 13 cross-sectional and
1 case-control studies representing 9 countries. The
sample size ranged from 52 to 6237. The age of the
participants ranged between 17 and 86 years. Of the in-
cluded studies, 2 examined the general population (42,
43), 13 examined the working population (34, 36–41,
44–49) and one evaluated elite athletes (swimmers)
(35). Clinical diagnostic tests (Hawkins-Kennedy/
Neer’s test/Empty can/painful arc/resisted abduction,
internal rotation, external rotation or forward flexion
of the shoulder) were performed in 14 studies to de-
termine the diagnosis of rotator cuff tendinopathy, and
2 studies combined the use of clinical diagnostic test
and imaging to confirm the diagnosis of rotator cuff
tendinopathy (38, 42). Details of the diagnostic criteria
of each study are summarized in Table III. The overall
prevalence of rotator cuff tendinopathy ranged between
1.2% and 40% (general population = 1.2% (43), wor-
king population = 2.0–40% (34, 36, 37, 39–41, 44–49)
and elite swimmers = 1.7% (35)).
Narrative synthesis
Factors that were associated with increased risk of
rotator cuff tendinopathy are summarized in Table III.
Overall, 22 potential risk factors were identified and
were categorized into:
Demographics. Age above 50 years old (OR ranged
between 1.03 and 4.10) (34, 36, 38, 41, 44, 49); Female
sex (OR = 0.33, 95% CI = 0.14–0.78) (37); and Previous
shoulder injury (χ 2 = 24.9, p < 0.001) (35).
Systematic diseases. Diabetes (OR ranged between
2.90 and 4.70) (41–44); Hypertension/cardiovascular
disease (OR = 4.49, 95% CI = 1.66–12.2) (34); and
Osteoarthritis (OR = 2.39, 95% CI = 1.41–4.07) (42).
Anthropometrics. Shoulder instability (χ 2 = 30.5,
p < 0.001) (35); and Increased waist circumference
(OR = 2.0, 95% CI 1.10–3.50) (43).
www.medicaljournals.se/jrm
Mechanical factors. Work with the shoulder above 90°
(OR ranged between 3.30 and 4.70) (36, 41, 42, 49);
Repeated and sustained arm abduction (OR = 2.60, 95%
CI 1.40–5.0) (36); Heavy manual work (OR = 3.81,
95% CI 1.93–7.51) (42); Repetitive work (OR ranged
between 2.90 and 3.12) (39, 44); High frequency of
work (OR ranged between 2.02 and 3.35) (39, 45, 46);
High force exposure of work (OR ranged between 3.33
and 4.80) (39, 45); and Vibration work (OR ranged
between 1.04 and 2.83) (45, 47, 48).
Sports activities. Swimming (OR = 1.98, 95% CI
1.11–3.53) (42); and Weight training (OR = 2.32, 95%
CI 1.07–5.05) (42).
Psychological factors. High psychological demand
(OR ranged between 1.30 and 3.19) (40, 44, 49); Low
co-worker support and work with temporary workers
(OR = 2.20, 95% CI 1.20–4.20) (36); Low job control/
decision authority (OR ranged between 0.79 and 6.68)
(40, 44–46); Poor safety commitment (OR = 1.66, 95%
CI 1.16–2.38) (40); and Job dissatisfaction (OR = 3.11,
95% CI 1.52–6.37) (34).
Meta-analysis
An OR with 95% CI was available for only 10 of the
included studies due to limitations in the data presented
(34, 36–38, 41–44, 46, 49). Thus, pooled meta-analysis
was feasible for only 5 factors. These were age above
50 years (Fig. 2), female sex (Fig. 3), diabetes (Fig. 4),
working with the shoulder above 90° (Fig. 5), and psy-
chological demand (Fig. 6). Strong evidence showed that
age above 50 years among the working population (OR
3.31 (95% CI 2.30–4.76, Z = 6.43, p < 0.001) and diabetes
among the general and working population (OR 2.24,
95% CI 1.37–3.65, Z = 3.21, p = 0.001) were associated
with increased risk of rotator cuff tendinopathy, and the
between-study heterogeneity for both factors was low
(between study I 2 index=0%) so pooled analyses were
deemed valid. Moderate evidence showed that working
with the shoulder above 90° was revealed to be associated
with increased risk of rotator cuff tendinopathy among
the working population (OR 2.41, 95% CI 1.31–4.45,
Z = 2.82, p = 0.005), but high levels of between-study
heterogeneity (I 2 index = 83%). Nevertheless, female
sex (OR 1.31, 95% CI 0.83–2.05, Z = 1.15, p = 0.25) and
psychological demand (OR 1.40, 95% CI = 0.95–2.08,
Z = 1.69, p = 0.09) may not be associated with increased
risk of rotator cuff tendinopathy among the working
population, and the between-study heterogeneity was
moderate (I 2 index = 69% and 64%, respectively).