Endometriosis is not a 'career woman's disease', as it used to be known, but it very much does impact the careers of women.

A two-year-long study among almost 4,000 women in Finland has found those with endometriosis took 10 or more sick days, even at the age of 46, compared to those without endo. They also claimed, on average, 10 more disability days.

The good news is that scientists in Finland found no patterns of early retirement or unemployment when examining data from 348 participants with endometriosis. Still, this research was conducted in a country with relatively good healthcare, welfare, and retirement systems. It's unclear if that would be the case elsewhere.

"To our knowledge, this is the first general population-level study on the association between endometriosis and work ability," the authors write.

Endometriosis is a chronic and often painful disease that has no known cause or cure, despite a rich history of possible theories. For several decades, medical textbooks actually referred to endometriosis as a 'career woman's disease'.

Traditionally, it was thought that those Type-A individuals who put off marriage and pregnancy to pursue a career were more likely to develop the illness. As a result, patients were often given only two treatment choices: get pregnant or get a hysterectomy.

Today, the notion of a 'career woman's disease' has been thoroughly debunked. Emerging research now suggests it's not a woman's career path that shapes her disease but the other way around.

A 2011 analysis across ten countries, for instance, found each woman impacted by endometriosis lost an average of 10.8 hours of work weekly, mainly because their symptoms made it much more difficult to complete tasks.

In 2013, a study in the United States found patients with endometriosis experienced significantly more sick days each year. Even when they were well enough to work, their pain and fatigue made it much harder.

What's more, the longer it took for a person to get diagnosed with endo, the more likely it was for their profession to suffer in the long run.

Retrospective studies suggest people with endo generally receive a lower annual salary and experience slower salary growth.

Even in countries like Switzerland, Germany, and Austria, which have greater social welfare, women with endometriosis say they are less able to work in their desired profession because they live with chronic pain and fatigue.

These previous studies almost all agree that endometriosis has a serious impact on a person's work life, but the new Finnish study is the first to examine how older professionals are impacted, too.

Even though the symptoms of endo can often ease with age and menopause, their findings suggest people with endo continue to take substantially more sick days than other women at age 46.

Luckily, the disease doesn't seem to cause unemployment or force early disability retirement, but endometriosis results in a large spectrum of symptoms and severities.

While treatments like surgery or hormones might work for some, others will continue to experience chronic pain with little relief.

It makes sense then that those with more mild cases are also the ones that remain employed at a later age, even if they do take far more sick days than most.

"Thus," the authors admit, "women still employed at a late fertile age, after hardships related to endometriosis, might have the mildest phenotypes of the disease or be otherwise healthy, which might underestimate the actual effects of endometriosis."

Other people with more severe cases, on the other hand, might have lost their jobs or had to retire earlier in life, so they were missed in the study.

Further research is needed, especially at a population level, so we can quantify the effects of this very common disease.

For too long, complaints from endometriosis patients have gone unheard or have been dismissed entirely. It's about time we started paying attention.

The study was published in Acta Obstetricia et Gynecologica Scandinavica.