(CNN) The real impact of menstruation on women and society is underestimated, researchers say, as a new study suggests period pain is linked to nearly nine days of lost productivity a year in workplaces and schools.
Researchers surveyed 32,748 Dutch women between the ages of 15 and 45 to evaluate lost productivity associated with menstrual symptoms. They measured both time off from work or school, as well as working or studying while feeling ill -- what the study termed "presenteeism."
The study, which was published Thursday, found that around 1 in 7, just under 14%, had taken time off from work or school during their period and 3.5% said that this happened during every, or nearly every, menstrual cycle.
Some 81% of the Dutch women said they had been less productive as a result of their menstrual symptoms. On average, the researchers calculated, women were absent from work or school 1.3 days per year because of their period and, on average, productivity loss was equivalent to 8.9 days per year.
"Women said that they weren't as productive as they could be while at work -- they needed to go to the toilet every hour or they had a headache and couldn't concentrate," said Theodoor Nieboer, an author of the report and a gynecologist at the Radboud University Medical Center in the Netherlands.
He added that women under the age of 21 were around three times more likely than older women to say they had taken time off because of their menstrual symptoms.
The study, which was published in the BMJ Open medical journal, is the largest of its kind. It also found that when women did call in sick because of period pain, only 1 in 5 told their employer or school the real reason for their absence.
What's more, 68% of respondents said they wished they had the option of more flexible hours to work or study during their period.
"Despite being almost two decades into the 21st century, discussions about [symptoms] may still be rather taboo," Nieboer said. "There's a need for greater openness about the impact of menstrual symptoms on work, and companies need to be more open about this with their female workers."
Nieboer said he did fear that some employers might use the insights from the survey to discriminate against women, but added this was not the right message to take away. Around the world, 1.8 billion women menstruate. The real impact of menstruation was under-appreciated, he said.
"Menstruation-related symptoms cause a great deal of lost productivity, and presenteeism is a bigger contributor to this than absenteeism," he said.
"However, we shouldn't lose sight of the fact that there's plenty of reasons why men might be unproductive in the workplace."
The authors said that their study did have some limitations.
It relied on what women said in the survey rather than measuring actual productivity loss. Also, the respondents were recruited via social media, which may have introduced an element of selection bias, with women with more debilitating menstrual symptoms potentially being more likely to take part.
Menstrual or period leave has been presented as a possible solution for the occasions when a woman might need to stay home due to having uncomfortable symptoms related to her menstrual cycle.
Across several Asian countries, menstrual leave is already offered to working women, Danielle Keiser told CNN last year. Keiser is founder of a global women's health organization called the Menstrual Health Hub.
There are menstrual leave policies in Indonesia, Japan, Vietnam, South Korea, Taiwan and China, according to records from the Menstrual Health Hub, although it's often an entitlement that women don't feel they can take in male-dominated workplaces.
In other parts of the world, menstrual leave policies have emerged more on a company-by-company basis. For instance, Coexist, a group based in the United Kingdom that hosts community spaces, allows employees who opt into its period policy to take time off, work from home, or consider other options such as altering their working hours during their periods.
And in Australia, the Victorian Women's Trust, an advocacy group, offers employees paid days off for painful periods.