No proof that bad relationships raise blood pressure

"If you have ever blamed your partner for making your blood boil, a new study could be the evidence you need to prove it's true," Mail Online reports. But the association between stress and blood pressure is much less clear-cut than the Mail suggests.

The study involved 1,356 older married couples in the US. They completed two sets of assessments four years apart. The assessments asked questions about their stress levels and marital satisfaction, and also measured their blood pressure. The researchers then looked at how these factors were related to each other. 

The results were quite a mixed bag, which makes it difficult to draw any firm conclusions from them. They generally suggest that husbands had higher blood pressure if their wives were more stressed.

If wives were stressed, their blood pressure was lower if their husbands were also stressed. Poor relationship quality was only detrimental to blood pressure if both partners felt negative about the relationship.

But this study has many limitations, including the difficulty in establishing whether blood pressure changes were definitely seen after stress or relationship problems. We also cannot tell whether a person actually had clinically high blood pressure.

Overall, this study will be of interest to social scientists, but provides no proof that the stress of a bad relationship causes high blood pressure. 

Where did the story come from?

The study was carried out by researchers from the University of Michigan. Data for the study was drawn from the Health and Retirement Study, which is funded by the US National Institute on Aging.

It was published in the Psychological Sciences and Social Sciences series of The Journals of Gerontology.

Mail Online took the results of this study at face value and did not consider its limitations, or explain that there is no proof of cause and effect. 

What kind of research was this?

This was an ongoing cohort study that gathered data on marital status and psychosocial health at one time point, and then looked at whether this was associated with changes in blood pressure over time.

Stress in its various forms has often been thought to have various detrimental effects on health and wellbeing. This study aimed to look at chronic stress associated with a poor marital relationship, and specifically how this was associated with changes in blood pressure.

The researchers expected to see evidence that more stress was linked to higher blood pressure, but also wanted to see if the effects differed between men and women.

The main problem with a study like this is that it can't prove cause and effect, as there are likely to be many other unmeasured factors involved (confounders). 

What did the research involve?

The study used participants in the ongoing nationally representative Health and Retirement Study (HRS) in the US, which includes people born before 1954.

Participants are interviewed every two years. In 2006, psychosocial questionnaires were given in face-to-face interviews. These included an assessment of partner relationships and stress. Participants also had body measures taken, including blood pressure.

Chronic stress was assessed by asking the people involved about whether seven stressful events had been ongoing for at least 12 months:

• physical or emotional problems (in a spouse or child)
• problems with a family member's alcohol or drug use
• difficulties at work
• financial strain
• housing problems
• problems in a close relationship
• helping at least one sick, limited, or frail family member or friend on a regular basis

They responded either "no", "it didn't happen", or "yes, it did". If they responded "yes", they rated this as "not", "somewhat", or "very upsetting".

They also completed a set of questions specifically looking at relationship quality, including the following questions:

• How often does your spouse or partner make too many demands on you?
• How often does he or she criticise you?
• How often does he or she let you down when you are counting on them?
• How often does he or she get on your nerves?

This study used data from the repeat assessments taken four years later in 2010 to see if blood pressure and psychosocial factors changed over time, and how they were associated with each other.

The researchers took the potential confounders of age, ethnicity, education, length of marriage and use of blood pressure medication into account. 

What were the basic results?

A total of 1,356 married couples completed the two assessments in 2006 and 2010. The average age for men was 66 and 63 for women, and they had been married for an average of 36 years.

Average blood pressure (looking at only the upper systolic figure) was slightly higher for husbands (132 in 2006 and 134 four years later) than for wives (127 to 129).

Just over a third of husbands and just under a third of wives were classified as having high blood pressure at both time points. Blood pressure was shown to significantly increase over time in both partners.

Overall, couples reported low levels of chronic stress and low relationship quality, though wives tended to report more of both of these problems than husbands.

The most common problems were the ongoing health problem of a spouse or child, ongoing financial strain, and helping at least one sick or disabled person.

The researchers also found significant associations between reported chronic stress, gender and blood pressure. Some of the findings included:

• husbands had higher blood pressure when their wives reported higher stress
• husbands reporting greater stress had lower blood pressure if their wives reported lower stress
• wives reporting greater stress had lower blood pressure if their husbands reported more stress

This was interpreted as meaning that husbands appear to be more stressed by their wives' stress than the reverse. Wives' stress, meanwhile, seemed to be "buffered" by more stress in the husband.

Looking specifically at questions on relationship quality, the researchers found that if one partner reported negative relationship quality, their blood pressure was higher if the other partner also reported negative relationship quality.

Blood pressure was lower if the partner reported less negative relationship quality. There were no significant effects by gender.

The researchers interpreted this as meaning that higher levels of negative relationship quality are only detrimental when both partners feel negative about the relationship. 

How did the researchers interpret the results?

The researchers concluded that their findings indicate that in a marriage, "(a) stress and relationship quality directly affect the cardiovascular system, (b) relationship quality moderates the effect of stress, and (c) the [two] rather than only the individual should be considered when examining marriage and health". 

Conclusion

Overall, this study looking at the relationships between reported chronic stress, relationship quality and blood pressure in a group of married couples will be of interest to social researchers. But readers should not read too much into these findings.

Though it is quite plausible that ongoing stress can have a detrimental effect on your health (particularly your mental health), this study does not prove that the stress of a bad relationship affects blood pressure.

This study had many limitations:

• It only looked at general associations between stress and relationship quality and blood pressure. It doesn't tell us whether psychosocial factors were associated with clinically meaningful changes in blood pressure, such as a person developing high blood pressure and requiring medication.
• It is difficult to establish a clear temporal relationship by only assessing psychosocial factors and blood pressure at just two time points. For example, we cannot say if a change in blood pressure was caused by the onset of stress or relationship quality problems. 
• The study was only able to ask fairly general questions about chronic stress and satisfaction in the relationship. These questions are unlikely to be able to capture the true nature of these issues and the extent of the effect this is having on the partner.
• It has not been able to take into account the complex influence that personality, physical and mental health, and lifestyle factors are likely to be having on any association between stress, marriage quality and health.
• This was a specific population sample of older married couples from the US who were married for a considerable length of time. The results may not apply to other nationalities, younger people, people married for less time, or people (of any genders) in a committed relationship who are not married.

This study provides no reliable evidence that you can blame your partner for your high blood pressure, as the media suggests.