Spouses who have a close relationship share many things - material and non-material, highs and lows. And when one spouse experiences chronic pain, it can have a ripple effect for the other spouse, affecting sleep and even increasing risks for health problems, say researchers from Penn State University.

A study recently published in the journal PAIN analyzed relationships in which one spouse experienced chronic knee pain. The researchers said they chose knee pain because it oftentimes causes difficulties staying comfortable in bed at night for many patients.

As a result, the team was able to study the effects on the other spouse's slumber.

The researchers, led by Dr. Lynn Martire, had 138 knee osteoarthritis (OA) patients and their spouses complete interviews and 22-day diaries. The subjects were all at least 50 years of age, lived with their partners and were either in long-term relationships or married.

Results from the study showed that the greater a patient's knee pain was at the end of the day, the worse quality of sleep their spouse experienced that night.

By contrast, the researchers noticed that the quality of sleep the spouse experienced did not equate to greater pain for the patient the following day.

So it appears that spouses who have pain are not affected by their partner's lack of sleep, even though the reverse is true.

The effects that the patients' pain had on spousal sleep were not a result of their own disturbances in sleep, the researchers said.

Dr. Martire noted that "spouses whose sleep is compromised may be less able to respond empathically to patients' symptoms and need for support," potentially also putting them at risk for "physical and psychiatric problems."

Greater closeness, less sleep, higher health risks

The researchers predicted that closer relationships would yield stronger results, and they were correct. They found that, with spouses who had a closer relationship, patient pain resulted in "less refreshing sleep for spouses."

The family experts warn that a groggy morning may not be the only effect on the spouses.

Dr. Lynn Martire said:

"Compromised sleep caused by exposure to a loved one's suffering may be one pathway to spousal caregivers' increased risk for health problems, including cardiovascular disease.

Our findings suggest that assessing the extent to which partners are closely involved in each other's lives would help to identify spouses who are especially at risk for being affected by patient symptoms and in need of strategies for maintaining their own health and well-being."

Research published in the Journal of the American Geriatrics Society in 2010 found that people caring for a spouse with dementia were more likely to develop it themselves.

Other research in the same year, however, reported positive elements to caring for a loved one.