People in marriages that steadily get sweeter have lower cholesterol and healthier weight than marriages that stay the same, according to a new 16-year study. But both were preferable to marriages that got worse: couples in them were more likely to develop high blood pressure later in life.

The study, published in the Journal of Epidemiology & Community Health, isn’t the first to suggest a link between marital quality and heart health. But most research has only looked at relationship satisfaction at one point in time, which makes it tough to determine whether marriage really has a protective effect on health, or if healthier people simply tend to be in happier marriages.

The new research measured marital ups and downs over the years to see if they went along with changes in heart health. To do so, researchers analyzed data from a long-running study of parents and children in Britain, in which fathers were surveyed about their marriage quality when their children were about 3, and again at about age 9.

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More than 2,000 people completed the survey once at the start of the study and again six years later, and 620 completed a follow-up analysis about a decade after the study’s start. At that time, the men had their blood pressure, resting heart rate, body mass index (BMI), cholesterol and fasting glucose levels measured, all of which indicate heart-disease risk factors.

Interestingly, there was very little difference in cardiovascular risk profiles between men who had consistently good relationships and those who had consistently bad ones during the study. But after adjusting for several influencing factors, including age, education, height and household income, the researchers noticed small but distinct patterns for men whose marriages had either improved or deteriorated during that time.

Men who said their marriage got better over the years had lower LDL—or “bad”—cholesterol and healthier weights (about 1 BMI unit less) at the end of the study, compared to those whose relationship satisfaction was consistently good for those years.

Meanwhile, those whose relationships got worse ended up with blood pressure an average of 2.74 points higher than those with consistently good marriages.

The researchers write in the paper that it makes sense that changes in marital quality could trigger these types of changes in cardiovascular health, and that they may not become obvious until after a “latency period” of several years.

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The fact that people in consistently good marriages fared no better than those in bad ones is contradictory to other research, but the researchers say their data about marital quality over time may paint a more complete picture. People in unchanging relationships may become habituated to their circumstances, the authors hypothesize, which may keep them from benefiting as much as those whose relationships steadily improve.

The study, however, can’t draw cause-and-effect conclusions. The authors point out that a large number of people dropped out before the final measurements were taken and that those who remained were more likely to report better marriage quality and fewer health and financial problems.

Because the people in the study are still relatively young, it’s also unclear whether more risk factors will actually lead to more heart disease. The researchers also don’t know if their findings would apply to women—but in the paper, they refer to a 2014 study in which worsening relationships were linked to worsening cardiovascular health more strongly for wives than for husbands. (Men “may be less likely to internalize a poor relationship than women,” the authors of that study speculated.)

There are still a lot of unknowns about the link between marital quality and heart health. But in their paper, the authors raise the possibility that working to improve the former may help improve the latter. “Further research needs to determine if effective marriage counseling, or when appropriate, abandoning a deteriorating relationship, has longer term physical health benefits over and above psychological well-being,” they write.

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