The Week That Wasn't: Scented Sleep, Beyond BPA, Insomnia-Diet Link

Ellie Kincaid


February 21, 2020

You may have recently seen articles about research showing that sleeping with a partner's scent improves sleep, another harmful chemical lurking in "BPA-free" plastics, and insomnia increasing sugar intake. Here's why you didn't see them on Medscape Medical News.

Scent of a Partner Improves Sleep

Psychology researchers ran an interesting experiment to see whether the presence of a romantic partner's scent affected how well people slept. They had study participants sleep on pillowcases consisting of t-shirts worn either by their partner or by a stranger. They then compared the participants' sleep quality, as measured by an actigraph sleep watch. A press release from the University of British Columbia quotes the study's lead author as saying that study participants "had an average sleep efficiency improvement of more than two per cent" when sleeping with their partner's shirt. That doesn't seem like a big effect, but the lead author also said the size is similar to that reported for oral melatonin supplements.

This research has been accepted for publication in the journal Psychological Science, according to the press release, but it has not yet appeared on the journal's website. That's a reason for us to pause before covering the research. Plus, the findings don't seem to translate into advice a clinician could give a patient. Presumably, those with romantic partners whose scent would improve their sleep are already getting a dose of it at night.

The Other Bisphenols

Because some plastics manufacturers have adopted alternatives to the endocrine-disrupting chemical bisphenol A (BPA) in products labeled "BPA-free," scientists have tested whether these alternatives are indeed safer. Researchers from the University of Missouri at Columbia fed two groups of female mice BPA and its alternative, bisphenol S (BPS), to study how the chemicals affected placental cells. They found similar changes to gene expression and other cellular qualities in the placentas of mice that ate BPA or BPS, compared with placentas from unexposed mice. BPS should be considered "as hazardous as BPA," they write in an article published in the Proceedings of the National Academy of Sciences.

The researchers note that placental development in humans is different from that in mice, so, beyond being an interesting bit of science, it's unclear what the implications of this study are for clinicians. We don't often cover preclinical research — because it's rarely relevant for our readers treating patients — and didn't see a reason to make an exception for this study.

Sleep and Diet

Poor sleep quality is associated with eating more food and lower-quality food, researchers report in the Journal of the American Heart Association. This finding comes from a study of sleep and cardiovascular risk in which the participants filled out questionnaires about their food intake and submitted self-reported measures of habitual sleep quality.

"By showing that poor sleep quality can be linked to overeating and poor diet quality in women, this study provides insight into a potential mechanism underlying the relationship between sleep quality and cardiometabolic health," the researchers write.

The researchers acknowledge that, because this study was cross-sectional, they cannot determine directionality or causality for the link they observed between lower sleep quality and diet. Future studies could test whether treatments such as cognitive-behavioral therapy for insomnia could help improve cardiometabolic health as well, but it would be premature to predict or encourage the approach on the basis of this study. We didn't think busy clinicians needed to pay attention to this line of research quite yet.

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