According to new research from The BMJ, at least 15 million adults may experience long-term smell deficiencies, while 12 million adults may struggle with taste. The research also found that only 74% of patients reported smell recovery and 79% reported taste recovery 30 days after initial infection, but recovery rates increased with each passing month.

Researchers reviewed 18 observational studies involving nearly 4,000 patients and learned that women were less likely to recover their sense of smell and taste compared with men. Meanwhile, patients who experienced “greater initial severity of smell loss and those with nasal congestion were less likely to recover their sense of smell,” according to a press release about the study.

Additionally, researchers believe most patients are anticipated to recover their sense of smell or taste within the first three months following infection, but “a major group of patients might develop long lasting dysfunction that requires timely identification, personalized treatment, and long term follow-up.”

Indeed, a change in one’s sense of taste or smell is just one of many symptoms of long COVID. Loss of taste and smell can also be the result of other illnesses, such as the common cold, flu, and sinus infections, as well as certain medications and age. Total loss of smell (anosmia) or loss of taste (ageusia) is uncommon.

For those looking to proactively repair their sense of smell or taste, there is olfactory training, which involves sniffing the same four scents every day, about 20 seconds for each scent, according to AbScent, a U.K.-based charity dedicated to ending smell disorders.

As rhinologist Dr. Zara Patel, a professor of otolaryngology, head and neck surgery, at Stanford University School of Medicine, recently told CNN, “The way I explain it to patients is if you had a stroke, and it made your arm not work, you would go to physical therapy, you would do rehab. That’s exactly what olfactory training is for your sense of smell.”