Study: Healthy romantic relationships may decrease stress and inflammation for breast cancer survivors

IN-DEPTH REVIEW OF RESEARCH

Study background:

A key factor affecting health is the intimate relationships in a person's life. People with satisfying relationships live longer and are healthier than people who are in dissatisfying relationships or are without a partner. Breast cancer survivors with supportive partners have lower stress than those with conflicting or avoidant partners.

Stress is associated with physical as well as emotional effects. Healthy people with elevated stress have increased levels of inflammation, seen as higher amounts of certain immune system components in the blood, e.g., C-reactive protein (CRP) or inflammatory cytokine proteins.

For people with breast cancer, inflammation is linked to poorer outcomes, including increased recurrence, increased rates of other diseases and earlier mortality. Prior studies showed that breast cancer patients with higher levels of stress have more inflammation that those with lower stress.

Stress may be a connector between relationship satisfaction and inflammation. People in less secure relationships have higher cortisol levels (a hormone that regulates stress responses) and poorer immune system function. Most previous studies focused on negative aspects of relationships, looking at the effect of  poor quality and hostile relationships on inflammation. In this study, researchers were interested to see whether positive, stable relationships benefit women with breast cancer.

Researchers of this study wanted to know:

Whether romantic relationships directly or indirectly affect inflammation by influencing stress levels. This study tests that idea that breast cancer patients who are satisfied in their romantic relationships also have lower stress and less inflammation.

Populations looked at in this study:

The study participants were 139 women with breast cancer (stage 0-3C) who were married or had a domestic partner. Average age was 55. Among participants, 85 percent were White, 7 percent were Black and 7 percent did not indicate their race.

These participants were enrolled in a larger study (209 women) on fatigue and immune function. Seventy of the women from the larger study were excluded because they were single, divorced or widowed. Women with a prior history of cancer other than skin cancer were also excluded, as were those with visual, hearing or cognitive problems that prevented completion of the study. Researchers enrolled participants in the study within three months of their breast cancer diagnosis and before they began treatment.

Study design:

Researchers met with each participant three times: before their cancer treatment began, and then at six months and 18 months after their treatment ended. At each visit, participants filled out surveys about their relationship satisfaction and their stress level in the week prior. The surveys allowed researchers to quantify relationship satisfaction and stress. Researchers also evaluated participants’ blood samples for proteins that are related to inflammation by measuring the levels of CRP and a combined measure of cytokine proteins. To look at the interaction between relationship satisfaction, stress and inflammation, researchers calculated the correlations using a statistical analysis called multilevel mediation analysis.

Researchers analyzed data from the group as a whole to see how these factors changed with time among the participants. They also looked at the data for each woman. This allowed them to track how a particular woman's relationship satisfaction changed during the study and how it impacted her own stress and inflammation rather than in comparison to other participants.

Study findings: 

Breast cancer survivors who were highly satisfied with their relationships had lower stress and lower levels of inflammation. A woman’s level of satisfaction in her romantic relationship is a good predictor of her inflammation levels.

• Satisfaction with relationships was highest before treatment and lower after treatment, but did not change between 6 and 18 months posttreatment.
• Higher stress was linked to greater levels of the inflammatory protein C-Reactive Protein (CRP)
• Higher stress was also linked to greater levels of inflammatory cytokines (interlukin-6, interlukin-1-beta and tumor necrosis factor alpha)
• Perceived stress decreased with time.
• Older women were more likely to have lower stress levels.
• Other factors, including body mass index (BMI, a measure of weight), education level and chemotherapy treatment were not associated with perceived stress.

Women with satisfying relationships had less stress, and women with less stress had lower inflammation. But does a woman's relationship satisfaction directly lead to lower inflammation? Do relationships affect stress, which in turn impacts inflammation? Or does stress affect relationships, which affects inflammation?

• Statistical analyses showed that relationship satisfaction indirectly affected inflammation. How much stress a woman perceived was associated with her level of inflammation.
• Statistical models supported the idea that satisfying relationships lead to lower stress, not that lower stress leads to relationship satisfaction.
• The group as a whole showed the same overall result: that relationships affected stress, which in turn affected inflammation. This result was also seen in individual women. Women who were more satisfied with their relationships during one one visit had lower stress and inflammation during that particular visit compared to other visits.

While these results show a correlation of relationship satisfaction, stress and inflammation, they do not necessarily indicate cause and effect. Whether this correlation indicates that relationship satisfaction leads to differences in stress levels will require additional testing (e.g., testing whether an intervention to improve relationship satisfaction leads to decreased stress).

Strengths and Limitations:

• This study followed women before and after breast cancer treatment. This prospective approach was a strength of this study.
• This study lacked a control group of women without breast cancer. While this was a limitation, related studies suggest that relationship satisfaction is linked to stress and inflammation in healthy women. Tracking data for each participant individually provided internal controls: the change of a particular woman's relationship satisfaction, stress and inflammation could be compared between visits. Women who were highly satisfied and less satisfied in their relationships were compared for the overall findings. These internal controls helped to support the study conclusions in the absence of a true control group.
• The lack of diversity among the participants was a limitation. The findings may not be representative of the population as a whole. The majority of women were White. Seven percent of participants were Black, but this isn’t significant representation. No Hispanic or Asian American women participated.
• Another impact of the lack of diversity pointed out by the researchers is factors that may be associated with stress and inflammation levels (other diseases, BMI, education level, cancer treatment) were similar among all of the participants. While researchers did control statistically for whether these factors might account for their observations, the lack of differences would obscure impacts that these factors may have. These factors may also impact inflammation, stress and/or relationship satisfaction.
• The number of participants was sufficient for the main point of the study, but it was too small to say anything about the impact of cancer subtype or stage.
• This study found correlations between satisfying relationships, stress and inflammation. These correlations may or may not be causal. These correlations must be tested with an intervention to determine if they cause the correlations observed. For example, whether interventions that improve relationship satisfaction directly decrease stress is unknown.

Context:

These findings fit well with prior research showing that relationships affect inflammation in healthy people. Similarly, this work confirms that relationships of breast cancer survivors affect inflammation.  This work also shows that the relationships of breast cancer survivors impact their perceived stress, and that in turn affects inflammation. Other research connects high inflammation to an increased risk of recurrence, other diseases and earlier death. This work suggests that interventions that lower stress may be beneficial in lowering inflammation and its physiological effects.

Conclusions:

Women who were more satisfied with their romantic relationships experienced less stress and lower inflammation.