The symptoms women experience on the verge of menopause could be vastly different from what they might expect, a new study says.

Women in perimenopause – the time leading up to their final period, as well as the year after – expect to be plagued with hot flashes and night sweats.

However, these women reported symptoms like exhaustion and fatigue far more frequently than those typically associated with menopause, researchers reported Jan. 28 in the journal Menopause.

"This study shines a light on how little we still understand about perimenopause and how much it affects people's daily lives," lead researcher Dr. Mary Hedges said in a news release. She’s a community internal medicine physician at the Mayo Clinic in Jacksonville, Florida.

For the study, researchers analyzed data gathered from more than 17,000 users of Flo, a women’s health application. Participants came from 158 countries.

The study specifically focused on more than 12,000 middle-aged women older than 35, who were approaching the age of menopause.

Those women said they most often had symptoms like fatigue (83%); exhaustion (83%); irritability (80%); low mood (77%); sleep problems (76%), digestive issues (76%); and anxiety (75%).

When asked which symptoms they associate with perimenopause, the women most often named hot flashes (71%), sleep problems (68%) and weight gain (65%).

But women who actually were in perimenopause listed their most common symptoms as exhaustion (95%); fatigue (93%); irritability (91%); sleep problems (89%); depression (88%); and brain fog (87%).

Weight gain affected 79% of women in perimenopause, hot flashes 75% and night sweats 70%, results showed.

“While hot flashes were the most widely recognized symptom, respondents aged 35 years or above most commonly reported experiencing fatigue, physical and mental exhaustion, and irritability,” researchers wrote in their paper.

More research is needed to better understand the symptoms women can expect through the different stages of menopause, researchers said.

They added that future studies also could look at how differences between women affect the symptoms they have, and what can be done to best ease their symptoms.