Machado GP, Gignac MA, Badley EM. Participation restrictions
among older adults with osteoarthritis: A mediated model of
physical symptoms, activity limitations, and depression. Arthritis
Rheum. 2008 Feb 15;59(1):129-35. [Pub
Med ID 18163415]
Objective
Research emphasizes the negative impact of osteoarthritis (OA) on social
participation, yet few studies have examined the roles of symptoms,
activity limitations, and depression in this relationship. The present longitudinal
study tested a model that hypothesizes that the relationship between
physical symptoms and later participation restrictions among older adults
with OA is mediated by activity limitations and depressive symptoms.
[more…]
That is, persons with OA who report greater pain, fatigue, and stiffness
are more likely to report difficulty with activities and greater
depression. In turn, activity limitations and depressive symptoms should
be associated with later participation difficulties, such as restrictions
in participating in community events, traveling, and visiting with family
and friends.
Methods
Participants were 184 community-dwelling senior adults (age ›55 years)
with a physician diagnosis of OA who were interviewed at 2 time
points 18 months apart. Measures included demographic variables; a derived
physical symptoms measure based on severity of pain, stiffness, and fatigue
in the previous week; and depressive symptoms measured by the Center for
Epidemiologic Studies Depression Scale. Measures of activity limitations
and participation restrictions were derived by factor analysis of questions
about difficulty in everyday life. Sequential multiple linear regression
analyses controlling for demographic and illness-related variables were
used to test for mediation.
[more…]
Six regression models, deemed direct effect models, were initially estimated.
The first three investigated whether severity of physical symptoms
was associated with depressive symptoms, activity limitations, and later
participation restrictions. Two other models investigated whether depressive
symptoms were associated with activity limitations and subsequent participation
restrictions. The last direct effect model investigated whether
activity limitations were associated with later participation restrictions.
Further regression analysis was performed to test for mediation. Based
on standard criteria for mediation, 4 additional regression models, deemed
mediated models, were estimated. The first of these models investigated
whether the effect of physical symptoms on activity limitations was mediated
by depressive symptoms (M1). The other 3 models investigated whether the
effect of physical symptoms on later participation restrictions
was mediated by activity limitations (M2), depressive symptoms (M3), and
both activity limitations and depressive symptoms (M4).
Results
Severity of Time 1 physical symptoms was associated with difficulties in
participation 18 months later. Sequential introduction of variables
showed that this relationship was partially mediated by Time 1 activity
limitations and Time 1 depressive symptoms. When both of these variables
were included in the model, the effect of symptoms severity was completely
mediated.
[more…]
Physical symptoms, depressive symptoms, activity limitations, and participation
restrictions were significantly correlated (p‹0.001) with one another,
fulfilling the first criterion to proceed in further tests for
mediation. Results from the direct effect models are shown in Figure
2A (see selected tables). After controlling for demographics and illness-related
variables, the estimates (ß) from the 6 models for the main independent
variables of interest were all significant at p‹0.01, fulfilling another
criterion for mediation. Having fulfilled all prerequisites to test for
mediation, final models including presumed mediators were tested and
the results are shown in Figures 2B and Table 3 (see selected tables).
Conclusion
This study demonstrates the importance of taking into account both the
physical (activity limitations) and psychological (depressive symptoms)
consequences of OA symptoms and suggests that these factors act
as a pathway to subsequent participation restrictions.
[more…]
Our results emphasize the importance of looking at disablement in OA
as a process and using conceptual models to examine the complexity
of the relationship among variables that measure distinct dimensions
of the consequences of this chronic illness. The finding that
activity limitations and depressive symptoms mediated the relationship
between physical symptoms and later participation restrictions allowed
us to go beyond the results of regular regression analyses. Specifically,
the findings of the current study suggest that symptoms severity does
not directly affect people’s ability to participate in social and
leisure activities. Instead, symptoms such as pain affect people’s
mood and ability to perform other types of tasks such as getting in and
out of a car and standing up from a chair. Difficulties with these tasks
and changes in mood, in turn, are related to social and leisure tasks.
In part, these results may be due to the fact that difficulties with basic
tasks are often part of more complex social and leisure activities.
The importance of mood in participation restrictions suggests that feelings
of upset related to pain may spillover into other areas of life,
leaving people with more difficulty engaging in other activities.
List of Tables and Figures (in the publication)
- Figure 1. Hypothesized model explaining the relationship between
measures of severity of physical symptoms, depressive symptoms,
activity limitations, and participation restrictions.
- Table 1. Sample characteristics (n=184).
- Table 2. Results of factor analysis of items related to difficulty
with activities and percentage of participants with any difficulty
in activities.
- Figure 2. Regression coefficients for A, direct effect models,
and B, mediated models.
- Table 3. Standardized regression coefficients for variables
in mediated models of participation restriction in older adults
with osteoarthritis.
Selected Tables from the Publication (with interpretation)
Figure 2. Regression coefficients for A, direct effect models,
and B, mediated models.
Having fulfilled all prerequisites to test for mediation, final models
including presumed mediators were tested and the results are shown
in Figure 2B (above) and Table 3 (below). The results from model M1 show
that, when accounting for depressive symptoms, the effect of Time 1 physical
symptoms on activity limitations was diminished from 0.50 to 0.42 (16%),
suggesting partial mediation in this relationship. In model M2, after adjusting
for activity limitations, the effect of physical symptoms on later participation
restrictions diminished by 19%, indicating that this relationship
was partially mediated by activity limitations. Model M3 showed that the
effect of physical symptoms on subsequent participation restrictions was
partially mediated by depressive symptoms as shown by a 29% reduction in
the coefficient. Model M4 showed the results of controlling for both mediating
factors (activity limitations and depressive symptoms): Time 1 physical
symptoms were no longer significantly associated with later participation
restrictions (B = 0.12, P = 0.15), corresponding to a 43% decrease from
the direct effect.
Table 3. Standardized regression coefficients for variables in mediated
models of participation restriction in older adults with osteoarthritis.
Supplementary Tables (with interpretation)
No supplementary information is available for this paper.
