In sickness and in health: Married couples' bodies start to match up biologically

A study of 1,500 wedded couples found remarkably similarities at a physiological level

Marriage, Wedding, Physiology, health, Shannon Mejia,

Nancy and Donald Featherstone, whose matching sets of identical clothing filled four wardrobes in their home [Modamob]

Walking through a busy thoroughfare on a sunny day, it’s often easy to spot the loving couples who’ve spent decades together. Regardless of whether they share a physical appearance, they’ve synced up in countless ways, sharing a rhythm of life that means their movements align in silent symmetry. And according to new research, those similarities are more than just skin deep.

In a paper presented at the AGM of the Gerontological Society of America, researcher Shannon Mejia and her University of Michigan team investigated the health indicators from more than 1,500 wedded couples from all across the US. The participants in the study were split into two subgroups: one covered couples who’d tied the knot 20 years before, while the other examined those who had celebrated their golden anniversary of 50 years. And the results showed that the wedded couples show remarkable similarities in their kidney function, cholesterol levels, and grip strength.

This phenomenon is referred to as ‘couples concordance in health’, with two leading theories as to why it happens; on the one hand, psychologists posit the possibility of mate selection, which often results in seeking out a partner who is from a similar pool as yourself, in terms of race, education and age. On the other hand, it could be based on the conditions and shared experiences couples share over a lifetime together, where health is the direct result of that time spent as a family.

A surprising outcome from this study was that it was actually the participants from the shorter-marriage group who showed greater levels of similarities, but Mejia says that this is somewhat biased – the 20-year married couples included partners who walked down the aisle as sprightly 25-year-olds, as well as those who made a more modest stroll at the age of 45. And when it came to those men and women who were older when saying ‘I do’, their lifestyle patterns and health habits were already well established before marriage.

The study goes against one of the prevailing tides held in medicine across the Western world, namely that our own health is an individual trait, not something we might share with a spouse. This “independence assumption,” as it is known, doesn’t tend to account for environmental factors, as Mejia told Science of Us.

“It’s something that researchers have learned to control for, because it’s known that people in groups are more similar to one another than a random person on the other side of the world,” Mejia says. “In our case, we’re looking at couples. We’re taking what used to be taken as a nuisance — the non-independence of the data — [and it] becomes our outcome of interest.”

All in all, it means that when you sit through the vows at a family wedding over the months to come, when the couples look into each others’ eyes and vow to love each other in sickness and in health, it turns out there’s a lot more to that that just tradition.

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