Illness uncertainty, partner caregiver burden and support, and relationship satisfaction in fibromyalgia and osteoarthritis patients




Fibromyalgia syndrome (FMS) is characterized by uncertainty in diagnosis, treatment, and outcome. This study assessed the role of uncertainty of illness in relationship satisfaction in patients with FMS and osteoarthritis (OA).


A total of 51 patients with FMS responded to self-report instruments assessing their uncertainty about their illness, functional ability, average pain, and relationship satisfaction. Their partners independently reported on their sense of caregiver burden and their supportiveness toward the patients. Thirty-two patients with OA and their partners served as a control group.


Patients' functional ability and pain were related to partner caregiver burden. Partner caregiver burden was related to lower levels of partner supportiveness for the FMS dyads, but not for the OA dyads. Relationship satisfaction of patients with FMS was related to their higher levels of uncertainty of illness in interaction with their functional disability and pain and their partners' supportiveness. Under high levels of uncertainty of illness, low levels of partner supportiveness were related to lower patient relationship satisfaction, whereas low levels of uncertainty of illness were significant interacting variables in the OA sample.


The results suggest that uncertainty of illness is a prominent feature affecting patients with FMS in their relationships with their partners. Suggestions for additional research to explore the role of uncertainty of illness in social relationships are presented, and the therapeutic implications for patient/partner relationships are explored.


Physical illness is a stressful experience for many medical patients and their partners. This stress is particularly exacerbated when the condition is chronic and debilitating because the illness often requires significant and permanent lifestyle changes. One such illness is fibromyalgia syndrome (FMS), a condition of pervasive, chronic muscular pain and fatigue, more prevalent in women than men (1). FMS is stressful because its etiology is unknown, treatment is not standardized and is often ineffective, and the course of the disease progression is not predictable. Due to this high level of uncertainty inherent in the illness, FMS is often called a “mystery disease” (2).

The negative effects of illness uncertainty are not unique to FMS. A number of studies on both human and animal populations indicate that uncertainty, per se, is disruptive and stressful (3–5) and that its elimination is a positively reinforcing event (6, 7). Uncertainty acts to sensitize the patient to the negative effects of an illness and is related to poor adjustment to illness and reactions to medical treatments (8–10).

FMS is particularly uncertain in comparison with osteoarthritis (OA), a well-understood condition of joint deterioration with reasonably standardized diagnosis and well-understood treatments that has levels of pain comparable with FMS. Patients with OA are less reactive to interpersonal stress than patients with FMS (11). Patients with FMS report significantly higher illness uncertainty than those with OA (12). Furthermore, patients with FMS report having more negative, interpersonally stressful experiences and lower positive affect than those with OA (13, 14).

FMS can be investigated as a dyadic problem as well as a problem for an individual patient. Neither the patient nor the patient's partner truly understands what is wrong, yet both have to adjust over time and under varying circumstances. Such conditions of uncertainty represent additional challenges for patients and their partners, and may impact both the individuals and their relationship above and beyond the comparatively straightforward effects of illness itself. Adjusting to FMS may have detrimental effects on the supportive nature of the relationship with corresponding challenges to relationship satisfaction.

The partner is a potentially important influence in the life of a patient with FMS. The disability experienced by a patient is likely to be significantly related to the sense of burden felt by the patient's partner, who in turn responds to the patient in ways that can be supportive (15), overprotective (16), or discouraging of activity (17). This may create a feedback loop such that patient disability changes partner perception and behavior, which in turn may have a detrimental effect on patient functioning. For instance, caregiver burden itself is positively related to the degree of patient disability (18). Additionally, supportive responses of the partner or caregiver are related to the functional (dis)ability of the patient (19, 20). Higher levels of disability tend to be related to increased partner supportive behaviors (21, 22).

How this feedback loop is affected by illness uncertainty is unclear. To date, no studies have investigated the effect of illness uncertainty when the partner's role is considered as a factor in patient's adjustment. Supportive behaviors on the part of caregivers are related to better patient physical adjustment (23), better hormone regulation (24), and enhanced marital satisfaction (25–28). These relationships may be especially strong in patients who depend more on their spouse for support. Patients with FMS have smaller, less diverse social networks compared with patients with OA, suggesting that they may be more dependent on their partners for support (11).

The current study aimed to clarify questions regarding the roles of patient characteristics and partner support in the patient's relationship satisfaction. We specifically selected patients with FMS and OA who reported in an initial screening that they were living with a partner who also agreed to participate in the study. We predicted that partners of patients with higher levels of pain and disability, especially in the patients with FMS, would report higher levels of burden, but that the sensitizing effects of high levels of illness uncertainty would cause partners' supportiveness to be more highly related to the FMS patients' relationship satisfaction. To expand the comprehensiveness of our assessment, we included 2 measures of patients' illness characteristics, their level of functional disability and a measure of their reported level of pain, and independent partners' reports of their supportiveness.



Participants were recruited from the Phoenix, Arizona region via advertisements, health fairs, and physician contacts for a large-scale study of biologic, psychological, and social variables in patients with FMS and OA. Potential participants who described themselves as having FMS and/or OA symptoms during screening were ultimately classified in either group based on physician confirmation. Because the OA patients also had chronic pain, the use of an OA sample served as a comparison group to give us some control over the variable of pain, a central hallmark of FMS. Only patients who answered that they were living with a spouse/partner at the time of the study were included in the study. The partners themselves were asked to participate, and responses were obtained only from patients and their partners who both signed their respective informed consent forms agreeing to participate.

A total sample of 128 patients were screened into the study. Within that group, a total of 51 patients with FMS and 32 patients with OA responded to the measures of this study; other participants responded to other sections of the study. Patients with FMS had been diagnosed for an average of 5.9 years, and those with OA for an average of 8.7 years; this difference was not significant (t = 1.89, not significant [NS]). The mean age of the patients with FMS was 51.9 years (range 35–69 years) and that of the patients with OA was 58.9 years (range 36—72 years); this difference was significant (t[81] = 3.89, P < 0.001). The proportions of patients who were married versus those living with a partner were nearly identical: 90% of patients with FMS and 91% of those with OA were married, with the remaining 10% of patients with FMS and 9% of those with OA currently living with a partner (χ2 = 0.01, P < 0.93, NS). The mean ages of the partners of the patients with FMS and OA were 53.7 years and 62.3 years, respectively, with the OA partners again being significantly older than the FMS partners (t = 3.38, P < 0.001). The groups were comparable in ethnicity, with 96% of the FMS sample and 100% of the OA sample endorsing their ethnic group as white. The groups reported similar levels of annual total family income, with their mean level falling in the $50,000–$59,000 range; the intersample difference was not significant.


Once screened into the study, all participants returned an informed consent form by mail. Upon receipt of these forms, participants were mailed an initial questionnaire that contained items to assess demographic data, health status (including average pain), and relationship satisfaction, among other variables. Along with this booklet, a separate booklet of instruments was included for reporting by the spouse/partner of the patient; measures of the partners' report of their supportive behavior and caregiver burden were included in this packet. Participants were instructed to complete their response booklets separately. Both booklets were collected when a trained clinician visited the home and conducted an extensive assessment of the patient's pain. At this time, the patient responded to other questionnaires, including the Western Ontario and McMaster Universities (WOMAC) instrument for assessing functional disability. Participants then completed and mailed back the uncertainty scale once during a 10–12-week period when they were completing daily diary interviews. All measures for this segment of the overall project were completed in a 3–4-month period for our participants. We assumed stability of relationships among the variables over this short period.

Assessment instruments.

Uncertainty of illness (patient questionnaire).

The Mishel Uncertainty of Illness Scale (MUIS-C) (8) is a 23-item self-report questionnaire containing questions assessing several dimensions of illness uncertainty (ambiguity, complexity, and unpredictability of symptoms). Previous studies have shown the MUIS-C to be a reliable and valid measure of illness uncertainty across a number of chronic disease states (29–32). The measure has demonstrated good alpha reliability estimates for a variety of illness populations (9, 33).

Relationship satisfaction (patient questionnaire).

An 11-item short form of the Locke/Wallace Marital Adjustment and Prediction Scale (34) provided a measure of the patients' satisfaction with their partner relationship in such dimensions as family finances, friends, ways of dealing with in-laws, etc.

Functional disability (patient report).

The WOMAC (35) includes a 17-item scale of patient reports of difficulty in performing daily activities of self maintenance. Higher scores on this variable are related to poorer levels of physical functioning.

Average pain (patient report).

During the initial screening interview, the patients responded to the following question concerning their pain: “Please choose a number between 0 and 100 that best describes the average level of bodily pain you have experienced over the past week due to your fibromyalgia/osteoarthritis. A zero (0) would mean ‘no pain’ and a one hundred (100) would mean ‘pain as bad as it can be.’”

Caregiver burden (partner report).

The partner report of sense of caregiver burden was assessed by the Poulshock and Deimling 19-item Caregiver Burden Scale (36). The items assessed limitations of activities, lack of time for self, and negative feelings related to the care provided to the partner.

Partner supportive behaviors (partner report).

The support provided by the partner to the patient was assessed using a modification of the social support items of the scale developed by Manne (37). The 12 items were modified to reflect general partner behavior and assessed partner availability as well as emotional and instrumental support provided by the partner in the past month.


The study's variables were first tested for their distributional properties, and all variables were well within acceptable range of skewness and kurtosis. Alpha consistency values were also tested and found to be acceptable. The major analyses proceeded in 3 phases: testing for mean level differences between the FMS and OA samples on all of the study's variables, testing for the zero-order Pearson correlation coefficient relationships on each of the predictor variables on relationship satisfaction, and tests of partial relationships through multiple regression predictions of relationship satisfaction.

Intergroup differences

The mean ± SD and range values for all study variables for both patient groups are displayed in Table 1. Tests of significance of mean differences also are reported. As shown in Table 1, the patients with FMS reported significantly higher illness uncertainty. The samples differed significantly in average pain, but not in functional disability.

Table 1. Significance of differences (t-tests) between patients with FMS and OA on the study's main variables*
VariableFMS (n = 51)OA (n = 32)t
  • *

    Values are the mean ± SD unless otherwise indicated. Ranges for the variables: uncertainty (1.5–4.2), disability (1–4.6), pain (4–100), caregiver burden (1–3.9), supportiveness (1.8–5.0), relationship satisfaction (0.7–5.3). FMS = fibromyalgia syndrome; OA = osteoarthritis.

  • P < 0.001.

Uncertainty of illness2.94 ± 0.562.54 ± 0.46−3.40
Functional disability2.75 ± 0.782.44 ± 0.71−1.80
Average pain60.80 ± 19.7346.22 ± 25.17−2.94
Caregiver burden (partner)2.07 ± 0.741.84 ± 0.55−1.42
Supportiveness (partner)3.40 ± 0.763.41 ± 0.660.08
Relationship satisfaction3.90 ± 0.854.10 ± 0.711.08

Intervariable relationships.

The basic intercorrelations and alpha consistency values (total sample of 83) for the variables are presented in Table 2, with the FMS sample above the diagonal and the OA sample below it. The alpha values are displayed on the diagonal, and showed acceptable levels of reliability in the range 0.86–0.95.

Table 2. Intercorrelations and alpha values of all study variables*
VariableUncertainty of illnessFunctional disabilityAverage painCaregiver burdenPartner supportivenessRelationship satisfaction
  • *

    Data for the fibromyalgia syndrome sample are above the diagonal; data for the osteoarthritis sample are below. Alpha for the combined sample are displayed in the diagonal in parentheses.

  • P < 0.001.

  • P < 0.01.

  • §

    P < 0.05.

  • P < 0.10.

Uncertainty of illness(0.86)−0.15
Functional disability−0.12(0.95)0.710.45−0.20−0.30§
Average pain0.260.55(–)0.22−0.19−0.37
Caregiver burden−−0.48−0.54
Partner supportiveness−0.02−0.37§0.240.16(0.87)0.27
Relationship satisfaction−−0.130.35§(0.88)

In the basic correlations, lower levels of relationship satisfaction were related to poorer WOMAC functioning and to higher average pain in the patients with FMS. However, for the patients with OA there were no significant correlations between either physical condition variable and the patients' relationship satisfaction. The differences between the FMS and OA correlations for the WOMAC variable and relationship satisfaction were significant (z = 2.01, P < 0.05) and they were also significantly different for the average pain correlations (z = 2.27, P < 0.05). Therefore, the patients with FMS showed a significantly greater negative relationship of their functional disability and their average pain with their relationship satisfaction than did the patients with OA.

The data in Table 2 show that the partners of the patients with FMS and OA reported different relationships between their sense of caregiver burden and their partners' physical conditions. The FMS partners' reports of burden were related to poorer levels of the patients' WOMAC functioning (r = 0.45, P < 0.05), and there was a trend for the partners' caregiver burden to be related to the patients' average pain (r = 0.22, P < 0.06). The OA partners' data did not demonstrate any significant relationships between their caregiver burden and any other of the OA patient variables.

Finally, the relationship between partners' caregiver burden and their supportiveness of the patients also varied between the FMS and the OA partners. Although the correlation for the OA sample was not significant, the correlation of −0.48 was significant for the FMS sample (P < 0.01), and the difference between the correlations also was significant (z = 2.40, P < 0.01). FMS partners tended to be less supportive as they felt greater caregiver burden, a pattern not demonstrated in the OA partners.

Multiple regression predictions of relationship satisfaction.

As noted earlier, the FMS and OA samples differed significantly in age, with the patients with OA being older than those with FMS. Age was controlled in each of the sets of multiple regression analyses (reported below). Because none of the analyses were altered significantly when controlling for age, the simpler equations without the inclusion of age are presented here.

The main sets of analyses involved testing the interacting effects of uncertainty, functional disability (or average pain), and the partner supportive behaviors as predictors of the patients' relationship satisfaction. Two 3-variable multiple regression tests were performed for each patient group, one for the pain and one for the functional disability independent variables (Table 3). All main effect terms were centered prior to entry into the prediction equations, and any resulting significant effects were examined by the procedures recommended by Aiken and West (38).

Table 3. Results of multiple regression equations predicting patient relationship satisfaction for both patient groups*
VariableFMS sampleOA sample
  • *

    Values are entered from the full prediction equations. FMS = fibromyalgia syndrome; OA = osteoarthritis; WOMAC = Western Ontario and McMaster Universities functional disability instrument.

  • P < 0.05.

  • P < 0.01.

Test for functioning          
 Step 1          
  WOMAC functioning−0.424.66   0.060.10   
  Illness uncertainty−0.060.14   −0.281.91   
  Partner support0.
 Step 2          
  Functioning × illness uncertainty0.050.08   0.040.04   
  Functioning × partner support−0.221.49   −0.261.32   
  Uncertainty × partner support0.364.930.230.091.44−0.424.190.340.161.94
 Step 3          
  Functioning × uncertainty × support0.−
Test for pain          
 Step 1          
  Average pain−0.448.10   0.060.13   
  Illness uncertainty−0.222.18   −0.6111.64   
  Partner support0.181.600.
 Step 2          
  Pain × uncertainty−0.160.97   −0.486.34   
  Pain × partner support−0.040.08   −0.120.56   
  Uncertainty × partner support0.292.700.240.061.00−
 Step 3          
  Pain × uncertainty × partner support0.344.420.320.084.420.498.370.560.168.37

Uncertainty of illness × functional disability × partner support.

The first main set of analyses involved the participants' reports of uncertainty of illness, their functional disability, and their partners' separately assessed supportive behavior as the independent variable predictors, and the patients' reports of their relationship satisfaction as the dependent variable; these were run separately on each sample of participants. There was one significant double interaction of illness uncertainty and partner support within each sample. Although the same interaction was significant for both groups, probing for the source of the significance revealed that very different patterns were involved in the interactions. For clarity of graphic presentation, Figure 1 combines each of the significant double interactions into 1 display. The regression slopes of support across levels of uncertainty were opposite for the FMS and OA samples. For the patients with FMS, low levels of support were related to lower relationship satisfaction when uncertainty of illness was high, but for the patients with OA, higher levels of support were related to higher relationship satisfaction when uncertainty was low; functional disability was statistically controlled for in these effects.

Figure 1.

Graphic display of the double interactions of uncertainty of illness and partner supportiveness on relationship satisfaction for the patients with fibromyalgia syndrome (FMS) and osteoarthritis (OA). Solid line = low uncertainty; dotted line = high uncertainty.

Uncertainty of illness × pain × support.

The structure of the previous analysis was repeated in this analysis, but functional disability was replaced by the patients' average bodily pain. The 3-way interaction of all predictors was significant for both patient groups. The results are displayed graphically in Figure 2 for the FMS group and Figure 3 for the OA group.

Figure 2.

Graphic display of the regression prediction equation for the relationship satisfaction of the patients with fibromyalgia syndrome. Solid line = low average pain; dotted line = high average pain.

Figure 3.

Graphic display of the regression prediction equation for the relationship satisfaction of the patients with osteoarthritis. Solid line = low average pain; dotted line = high average pain.

Under conditions of high uncertainty of illness and high levels of pain for the FMS sample, lower levels of partner support were related to poorer levels of relationship satisfaction. Conversely, higher support was related to higher satisfaction. None of the other regression slopes for the patients with FMS were significant. This pattern was not reflected in the results for the patients with OA. For the OA group, lower support was related to lower levels of relationship satisfaction under conditions of low uncertainty of illness and low pain. No other regression slopes were significant for this sample.


This study was designed to dissect the complexities of patient characteristics and partner support occurring in FMS and OA. Previous research (12) showed that uncertainty of illness in patients with FMS correlated with a wide range of wellbeing variables such as depression, anxiety, and avoidant and passive coping. This study extended that line of research into the domain of social relationships, specifically to the variables involved in a patient/partner dyad. Given the mysterious nature of FMS, we focused specifically on how uncertainty of illness in the patients with FMS would affect their judgments of their relationship satisfaction. The design included a comparison group of patients with OA whose illness is reasonably well understood and not characterized by great levels of illness uncertainty. The analysis of intergroup differences confirmed our expectation that the FMS sample would report a significantly higher level of illness uncertainty.

Partners of patients experiencing chronic pain conditions such as FMS or OA are subjected to some level of stress and sense of burden, and we speculated that their burden would be related to the functional disability and pain present in the patients. That effect was true for the patients with FMS, most clearly for the functional disability variable, and there was a tendency for the partners' sense of burden also to be related to the patients' average level of pain. In addition, increased partner burden was associated with lower levels of partner support. This pattern was not found in the OA partners, even though they reported comparable levels of caregiver burden. Caregiver burden in OA partners was unrelated to any of the other OA patient or partner variables. In contrast to FMS partners, there was a positive relationship between OA patients' functional disability and partner support such that OA partners were providing more support to partners with greater disability (independent tests not reported here found no relationship between the interactions of WOMAC functioning or average pain when interactions of these variables with uncertainty of illness were used as predictors of caregiver burden; the main effect correlations reported in Table 2 show the correlates of caregiver burden revealed in this study). The obviousness of disability to partners of patients with OA combined with the well-understood etiology of OA appeared to render feelings of burden a separate and distinct feeling, one not contingent on patient disability and pain compared with the contingent relationships found in the FMS sample.

The stresses of adjusting to chronic pain have been shown to be significant influences on relationship adjustment in patients who are living with partners (14, 39). Our results revealed several levels of dyadic factors influencing patient relationship satisfaction; although functional disability or level of average pain both interacted with patient uncertainty and partner support to predict relationship satisfaction for both samples, the patterns within each sample were different.

Relationship satisfaction was negatively related to both physical functioning and pain for patients with FMS, demonstrating a connection between patients' feelings about their partner and their own physical condition. Furthermore, in predicting relationship satisfaction, illness uncertainty of patients with FMS appeared to have a sensitizing effect on these patients when it was at higher levels. Specifically, lower levels of partner supportiveness were related to dissatisfaction only when patients' uncertainty was high. This was true at both high and low levels of functional disability but only at high levels of pain.

FMS partners reported being less supportive when they felt more burdened, and this was related to the poorer WOMAC functioning of patients with FMS and, to some degree, to patients' average pain. The interaction influencing patients' relationship satisfaction when uncertainty levels were high may reflect a heightened sensitivity to partners' responses at those times.

The patients with OA did not report a direct association between relationship satisfaction and supportiveness, and illness uncertainty showed significant interacting influence only at lower levels where higher OA partner support was related to greater relationship satisfaction after controlling for functional disability. The finding that OA partners reported being more supportive when patients' functional disability was higher most likely played a role in this interaction. The interaction between low uncertainty and partner support in predicting relationship satisfaction was also evident in patients with OA with low average pain whose feelings of relationship satisfaction were lower when their partners were less supportive.

In summary, we found a general pattern of patients with FMS having high levels of illness uncertainty, which influenced their dyadic relationship. When these patients were experiencing a greater level of illness uncertainty, their relationship satisfaction was generally lowered by their own physical condition, and was exacerbated by a lack of supportiveness from their partners. This finding is congruent with what we would expect based on other research on uncertainty of illness (8–10, 12). Uncertainty itself is stressful, and the supportiveness of partners is necessary for patients with FMS to have relationship satisfaction similar to that of patients experiencing less uncertainty. Patients with OA did not report high illness uncertainty and, overall, their uncertainty did not show any significant influences on relationship satisfaction when at high levels. Indeed, as shown in Table 2, illness uncertainty did not correlate with any other patient or spouse/partner variables for that group, a finding in line with our general understanding that uncertainty is not as prevalent an influence in patients with a physical illness as well understood as OA.

The results of this study encourage the use of multiple measures of physical condition when studying either group. We found somewhat different patterns of results with the WOMAC physical functioning and average level of pain variables. The FMS group reported higher levels of pain than the OA sample, whereas the groups did not differ in mean levels of functional disability. Interestingly, although disability was positively correlated with partner supportiveness for the OA sample, it was not significantly correlated for the FMS sample. OA partners, then, seem to be sensitive to patient disability in a way that is not characteristic of the FMS partners. Neither group of partners reported supportiveness to be related to the patients' levels of pain. Pain is a more private or less publicly visible aspect of either medical condition, so this effect is perhaps understandable. The FMS partners' sense of burden appears to have been the major determinant of their supportiveness rather than the patients' pain, an effect not found in the patients with OA. Pain seemed to be the more sensitive measure of the dynamics of the patient/partner interactions.

Therapeutically, our data suggest that interventions to improve patient relationship satisfaction might differ for these patient groups. Pincus and Morley (40) provide an elegant model of cognitive processing biases in chronic pain in which the schemas for pain, illness, and self become enmeshed over time, which serves to exacerbate distress and illness behaviors. For patients with FMS (and perhaps other patients for whom uncertainty is a key characteristic of their illness), the connection between their own poor physical condition and their relationship satisfaction suggests that their schemas of self, illness, and relationship should be disentangled, making each element more independent of the others. Their sensitivity related to high illness uncertainty seemed to activate the enmeshment of the illness and relationship schemas; their relationship satisfaction was more dependent on partner support, an association that did not hold when uncertainty was lower. Helping patients understand their uncertainty and how it colors their dyadic adjustment and their expectations from their partners may help weaken that association.

More information of how illness uncertainty impacts patients and their partners could be integrated into treatment programs (17). Partners themselves might be targeted for intervention. The fact that caregiver burden was related to lower supportiveness suggests that the partners might benefit from an intervention to reduce their sense of burden in response to the patients' disease exacerbations. This might be accomplished by encouraging the partner to maintain sources of enjoyment and validation outside of the relationship to defray some of the stress attendant upon living with a chronically ill loved one.

Some strengths and shortcomings of this study should be considered. Having the partners of the patients report on their levels of supportiveness rather than having the patients report on their own perceptions is a methodologic innovation that helps enhance the validity of the relationships assessed in the study. The more common methodology is to have the participant (in this case, the patient) report on the responses of others. This runs the risk that the relationships among variables could be artificially inflated by patients' consistency tendencies or influenced by their psychological and/or physical condition, thus potentially confounding the analyses. Such a risk is avoided by an independent assessment of partners. Our community sampling technique resulted in a predominantly white and middle-class sample, and our results should be tested in other patient populations. Finally, the data were interpreted within a causal framework, but cross-sectional methods cannot guarantee causal inferences. Experimental manipulations or longitudinal assessment methodology can more adequately address this question.


We thank Mr. Brendt Parrish for his contributions to the completion of this study.