For the research, 107 middle-aged, married couples were given glucose meters to keep tabs on their blood sugar. They checked it once in the morning on an empty stomach and then again just before bed every day for 21 days. The couples had been married, on average, for about 12 years.
Each husband or wife was also given a voodoo doll and told it represented their mate. At the end of each day, couples were asked to stick pins in the dolls to reflect the level of anger they were feeling toward their partners. They could use up to 51 pins at a time.
They were asked to complete this task privately since a glimpse at a much-punctured doll might set off a spat all by itself, thus skewing the study results. Each spouse recorded the number of daily pins used in the dolls.
At the end of the study, the couples visited a lab where they completed an additional test. The test pitted each spouse against each other in a video game. The winner of each round of the game was allowed to blast the losing spouse with an unpleasant noise through headphones. Within certain limits (researchers only let the noise level go about as loud a fire alarm), winners could choose how long and how loudly to blare the noise, which researchers recorded as another measure of aggression.
In reality, the couples were playing against a computer and it randomly chose the winner so each person heard the unpleasant noise about the same number of times.
At the end of the study, the researchers compared daily and average blood sugar levels with each partner's aggressive tendencies.
The result? People with lower blood glucose readings -- those that fell under 98 milligrams per deciliter (mg/dL) -- tended to be more aggressive toward their partners than those with evening readings over 121 mg/dL.
Those results remained significant even after researchers took into account how satisfied people said they were in their relationships, overall, and the sex of the partner who was being aggressive. Women tended to have higher daily pin-stick counts than men.
In a nutshell, the researchers said that means a hungry spouse is also more likely to be an angry spouse.
Their take home advice for marital bliss? Eat before you speak.
"Make sure you don't talk to your spouse about something important when you're hungry because hungry people are often cranky and irritable and angry, and we know that angry people are impulsive. Impulsive people say and do things they later regret," said lead study author Brad Bushman, a professor of communication and psychology at the Ohio State University.
The study appeared online April 14 in the Proceedings of the National Academy of Sciences.
There are some important limits to what the study can really prove, however. The study was observational, which means it can't prove cause-and-effect. It could be, for example, that stress and strife cause lower blood sugar levels, not the other way around.
And there wasn't any kind of a control (or comparison) group used, which means researchers don't have any idea how marital aggression might play out in couples who, for example, were asked to eat on a strict schedule to keep their blood sugar levels on a more even keel.
In spite of those limitations, an expert who was not involved in the study pointed to its creative methods.
"Voodoo dolls and loud noises provide novel ways to measure marital aggression. It's a useful approach, because it's not asking couples to describe their interactions -- it's a way to actually look at emotional responses," said Janice Kiecolt-Glaser, a professor of psychiatry and psychology at the Ohio State University who studies the health effects of marriage. She was not involved with the new study.
Another expert, who's a co-author of a book on marital arguing, also noted the unusual study set-up.
"I do have to say that sticking pins to a doll is a creative design -- and their methods are likely not full of 'holes' -- but other research shows that expressing anger leads to more, not less anger, so I would interpret the results with great care," said Howard Markman, a distinguished professor at the University of Colorado.
"Having romantic and healthy dinners with your partner ... banning conflict-oriented discussions during fun times, such as having dinner together, can prevent both anger and low blood sugar," Markman said.
For more tips on having a healthy relationship, visit the National Healthy Marriage Resource Center.
Copyright © 2014 HealthDay. All rights reserved.