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Being part of a couple comes with Netflix compromises, reduced closet space and unsolicited updates on indigestion. But it's also a boon to health, according to years of relationship research. To understand why paired-up people see more birthdays and less disease than their solo counterparts, scientists have pried into the private lives of twosomes and studied what goes down after the PJs come on. Sleep, they've found, is a relevant factor in how partners treat and understand each other. A decade of data has shown that good sleepers feel better about the state of their unions, and that strong unions beget restful nights. Except, the data doesn't apply to all 51 million couples across the country. Same-sex couples have been left out entirely.

The omission isn't an oversight, nor is it exclusive to sleep science. Prioritizing normatized populations is common across disciplines. Reliable studies hinge on comparisons of "like" subjects — apples to apples. And, while same-sex couples may be seen as the oranges to straight couples' apples, they're oranges who make up a growing subset of the nation. The U.S. is home to about 491,000 gay married couples, per a 2016 Gallup poll, not accounting for lovebirds who haven’t made it legal. 

Some researchers see the exclusion of gay couples in relationship studies as a hurdle to jump in time. Others are pushing to speed up the process and using new research methods to accommodate diversity without running afoul of bad science. Right now, we don’t really know how a bad night’s sleep affects a grumpy man with a wife versus a grumpy man with a husband. Men and women appear to experience shuteye differently, and it’s not clear how biological sex, gender roles and the thorny confluence of the two inform those differences. The existing research on dozing duos is, basically, science for straight people.

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What Science Says About How (Straight) Couples Sleep

At 63 years old, sleep science is a young field. Still, the subset of research focused on dyadic shuteye, meaning sleep in twosomes, or "dyads," is a zygote by comparison.

“The work on sleep in the social context within couples is very new,” said Wendy Troxel, a behavioral scientist at the RAND corporation and professor at the University of Pittsburgh whose name appears on the bulk of peer-reviewed sleep-and-relationship studies. “Most of my work has come out in the past 10 years, and there aren’t many other researchers doing the type of work that I am.”

A review of research published since 2007 suggests that Troxel and others have put out maybe 20 papers — including observational studies, data analysis and review papers — on dyadic sleep in committed couples. Collectively, the work offers a snapshot of sleeping a deux: Couples say they sleep better with their partners but objectively log better Zzzs when they split up. Rocky relationships predict rocky rest and vice versa. When marriages are strong, couples sleep better than single people do. When marriages are a mess, the trend dissolves. But pry open these general findings and the snapshot starts to pixelate.

Let’s say we wanted to deconstruct the influence of biological sex versus socially constructed roles. That actually is a really compelling reason, I think, to study sleep in heterosexual and same-sex couples simultaneously.

Not only does sleep affect certain couples more than others; the sleep-relationship link also manifests differently in men and women, and not in a way that's consistent. For wives, marital distress seems to drive sleep struggles more than marital joy does. In one recent study on married couples, Troxel associated wives' levels of insomnia with their husbands' ratings of marital satisfaction more than their own. Then again, when it came to sleep concordance — shared schedules, deep-sleep rhythms and the like — synced-up sleep reflected marital satisfaction in wives, not husbands. As the saying goes, happy wife, harmonized Zzzs? 

A good night's sleep is also linked to different behaviors for men and women. Hitting the sack boosted evaluations of marriage for men considerably more than for women in one study. And self-disclosure, "the act of revealing personal thoughts and feelings," emerged as a path to good shuteye for women, but not for men, in another study.

“Women’s traditional roles are as caretakers of the family,” said Troxel. “There are hypotheses that it’s one of the reasons women are more likely to have insomnia than men, because of that conditioned vigilance to be caretakers in the middle of the night.”

Studying sleep in couples is part of a bigger effort to figure out how relationship status informs health and wellbeing. On average, the 66 percent of Americans in long term, committed relationships will live longer, and with fewer health complications, than those who make a go of it by themselves. If probing couples' after-dark lives contributes to understanding the dynamics of relationships — strong and weak, blooming and fading — then that probing might have significant health outcomes.   

Across the body of work, however, wives are women with husbands and husbands are men with wives. While the research establishes big-idea points about sleep and relationships and hits on nuances in the intersection of biology and identity, it also uniformly leaves out gay couples. In fact, researchers only mentioned the absence of gay couples as a limitation of their work in one study. 

Excluding minority groups from a study may not render it incorrect. But, that doesn’t make the results broadly applicable. It all depends on the underlying question. 

To use an extreme example, let’s say a study on sleep and hate speech in urban America only included white people. If it found that participants who reported experiencing hate speech also reported insomnia, then we could, in theory, apply the findings to all victims of hate speech, across the race spectrum. But, given the world in 2016, and our country's history of racial tension, we know social context is important — too important to justify making the white-to-black leap. In fact, doing so would seem downright Drumpf-ian.

Troxel thinks it's reasonable to assume the big-picture takeaway from her work would apply across all couples. "My work focuses a lot on relationships that provide a sense of emotional safety and security, that should be beneficial for sleep.”

In other words, being in a good relationship should promote good sleep, and vice versa. But, beyond this broad finding, she does not think we know how the sleep-and-relationship dynamics of a husband-and-wife duo would translate to a gay couple. 

“I would be hesitant to generalize [the outcome of studies on heterosexual couples’ sleep] until we test it,” says Troxel, “and I think that’s what good science is about. Let’s say we wanted to deconstruct the influence of biological sex versus socially constructed roles. That actually is a really compelling reason, I think, to study sleep in heterosexual and same-sex couples simultaneously, provided that you have a large enough sample to get at that specific question.” 

Where Are the Same-Sex Studies?

 

In designing studies, Troxel has explicitly recruited people in heterosexual partnerships who don't have disorders of the mind or sleep.

“The reason my studies have been sort of focused on heterosexual couples only,” said Troxel, “is really due to the fact that I’ve focused on sleep within couples and there’s always a health outcome, in my case a cardiovascular health outcome.” 

Troxel’s work is funded by The National Heart, Lung and Blood Institute (NHLBI), the branch of the National Institute of Health (NIH) under which sleep research falls. To design a study that explores sleep, relationship functioning and cardiovascular health in couples, whether or homosexual or heterosexual, Troxel said she’d need “an enormously large sample” so she could tease apart how sex and gender affect sleep, via cardiovascular health. To flesh that out, she’d have to determine which physiological and behavioral differences are a product of being a biological male and which are a product of being the “man” in the couple. 

In Troxel’s research, a same-sex couple would be a confounder, which in an observational study is an unaccounted-for element that renders different groups, or members within one group, incomparable. In other words, it’s the quality that turns an apple into an orange. According to a 2011 paper, the term comes the Medieval Latin verb “confudere,” for “mixing.” 

It might be uncomfortable to think of a gay couple as a smear on validity, but researchers are working within an established paradigm for running experiments and making sense of the outcomes. They can try and break the mold, but there’s no guarantee someone will pay them to do it.

"It's not that I don’t want (to include same-sex couples). I would love to do that study," said Troxel. "I think it’s a completely compelling research question, to understand if similar dynamics would play out in a same-sex relationship."

If scientists seem fussy about the manner in which they collect data, then perhaps they’re justified.

To secure funding in a new area of research “you often have to establish that [the phenomenon you’re studying] is in fact a true thing, and then you get funding to do larger and more diverse samples," said Troxel.

Put another way: Science builds on itself, explained Heather Maranges, a psychology PhD student at Florida State University who co-authored the study on sleep and marital assessments: 

To ask and answer a new question, you need the scientific findings of the past to develop that question, decide how to test it empirically, and to develop hypotheses about its answer. The lion's share of relationship research has been done with heterosexual couples, and so that's the foundation that current research is built on, and so many more biological and social variables come into play that may make it difficult to start new research lines with non-hetero samples.

If scientists seem fussy about the manner in which they collect data, then perhaps they’re justified. In addition to securing funding, they bear the burden of getting things right. A flawed study might fade into the background. But, it could also become a source of authority, as was the case for a crooked 2012 study that claimed to show the harmful effects of same-sex parenting. The study relied on intel from adult children who retroactively dished on the same-sex relationships their parents may have once held. As methodologies go, this type of “proxy report” doesn’t pass muster. The findings were discredited, but not before they fueled a legal assault on same-sex adoption and marriage rights.

The Other Side of the Rainbow

New areas of science traditionally begin with explorations of “normal” subjects. In other words? White men. As researcher Nancy Walton wrote on her research ethics blog about past discrimination in clinical trials:

For many years in many studies, care was taken only to include participants who made up a relatively homogeneous group in order to minimize confounding factors. The result? We learned a lot about older, white males because they were the most dominant and powerful group. We learned about how heart disease affects older, white males. What a heart attack looks like in an older white male. How medications to treat chronic hypertension work in older, white males. You get the idea. Meanwhile a whole bunch of black men were dying from hypertension. Little to nothing was known about the disease, how to prevent it or treat it, in black men.

But, over the last three years, we have seen research methods adjust to shifting social realities. The recent surge in extra-marital cohabitation, for example, gave rise to new, better data about unmarried couples and ways to study them, as a 2015 analysis of research on same-sex couples showed. So, how and when can our current knowledge of rest and relationships become useful to the more-than 650,000 same sex couples hitting the sack in the US?

When old-school science doesn’t accommodate the world we live in, what’s a progressive researcher to do? Try a new method.

Rather than let science build on itself, and wait for research on heterosexual couples to mature, some researchers are moving into new territory now: straight and non-straight, together at last.

Studying people in pairs is tricky. A study subject is usually a single person. But, when the spotlight falls on dyadic behavior, two become one. Most traditional methods of analyzing dyadic data require members of dyads to be distinguishable from each other. When researchers explore the impact of gender on different sex-couples, they can tell halves of a couple apart by their sex. This doesn’t work for same-sex couples. 

So, when old-school science doesn’t accommodate the world we live in, what’s a progressive researcher to do? Try a new method. Katrina Walsemann, a population scientist at the University of Michigan, is in the middle of a study on marital interactions and sleep quality, in which she compares gay, lesbian and heterosexual couples. "Sleep problems are a significant public health problem, said Walsemann, "and sexual minority couples have been overlooked in research focused on sleep and relationship quality." 

Walsemann borrowed data from HARP, an ongoing project at The University of Texas at Austin that explores the health impact of marriage. The researchers behind HARP set out to figure out what members of long term relationships do that manifests in longer, less disease-ridden lives. How, for example, does having a spouse influence the way people eat or see doctors? And how does being in a heterosexual or same-sex marriage matter for men vs. women? 

"Having data that includes sufficient numbers of same-sex and opposite-couples has been relatively rare," said Walsemann. "It wasn’t until recently that the federal government started collecting information on sexual orientation on our national health surveys."

Walsemann is using an approach (pioneered by others) that explicitly considers the sex, gender and sexual orientation of each respondent and their spouse. By pulling out this information, researchers can figure out the significance of being a man or woman, being in a relationship with a man or woman, and being in a gay couple compared to a straight couple.

So, if the key difference in the impact of sleep on marital satisfaction has to do with biological sex, gay men and straight men would look similar. If the key is the sex of a significant other, gay men and straight women would look similar. And if the key is whether a couple is same-sex or different-sex, lesbian women and gay men would look similar.

Walsemann isn't willing to discuss results yet. But regardless of what the study shows about sex or gender, there's inherent value in learning how to investigate the world as it is, rather than as an all-apples version of how it might have once been. Research is supposed to challenge our beliefs and expland our knowledge. When the world changes, so too must science. And, as Troxel pointed out, the benefits of studying same-sex couples supersede intellectual expansion. 

“We know from heterosexual relationships that married people live happier, healthier, longer lives,” says Troxell. “And so, why wouldn’t we want to extend that to everyone?”

A wonderful thought, but will it get funded?