This Early MS Warning Sign Occurs in 80 Percent of Patients, Experts Say

You should talk to your doctor if you're experiencing this problem.

Multiple sclerosis (MS) is both an unpredictable and long-lasting disease, which makes it an unnerving diagnosis. Worse yet, MS is hard to diagnose, since its symptoms often mimic other common conditions, leading many people with MS to be frequently misdiagnosed. In fact, a June 2021 study published in the journal Neurology found that early MS symptoms are frequently missed for up to five years before patients get the proper diagnosis. To help you figure out what to look for, there's one symptom that occurs early in this central nervous system disease and affects four in five patients. Read on to find out the most common early symptom of MS.

RELATED: If You Notice This While Walking, It May Be an Early Sign of MS.

Nearly 80 percent of people diagnosed with MS first notice fatigue.

Depressed woman awake in the night, she is touching her forehead and suffering from insomnia

A 2021 study published in the Multiple Sclerosis Journal analyzed more than 200 MS patients the year after their diagnosis and found that the most common early symptom was fatigue. According to the National Multiple Sclerosis Society (NMSS), nearly 80 percent of people diagnosed with MS experience unexplained fatigue early on.

People with MS can have multiple types of fatigue, like sleep deprivation due to bladder dysfunction or nocturnal muscle spasms, or fatigue as a result of having to expend more effort just to accomplish daily tasks. But the NMSS says one type of fatigue, referred to as lassitude, is unique to people with MS. This kind of fatigue "generally occurs on a daily basis, may occur early in the morning, even after a restful night's sleep, tends to worsen as the day progresses, tends to be aggravated by heat and humidity, comes on easily and suddenly, is generally more severe than normal fatigue, and is more likely to interfere with daily responsibilities," according to the organization.

RELATED: Selma Blair Reveals the First Sign She Had Multiple Sclerosis.

MS may present as weakness or heaviness in your legs specifically.

Closeup shot of an unrecognisable woman rubbing her knee in pain while working from home

Fatigue related to MS typically happens when nerves deteriorate in the spinal column, which tends to result in weakness that is most noticeable in the legs at first, per the Physio Centers of Africa.

"Often people say that their legs feel heavy and they're hard to lift," Gloria Hou, MD, the medical co-director of the University of Washington Medicine Multiple Sclerosis Center in Seattle, Washington, told WebMD. "That's a very typical description for neurologic weakness."

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Heat sensitivity is another common MS symptom that shows up early on.

person enjoying the electric fan, cooling his face at home, during summer heat

Fatigue is not the only symptom the majority of MS patients experience early on. According to a 2018 study published in the journal Temperature, around 60 to 80 percent of patients with MS also experience a particular kind of heat sensitivity known as the Uhthoff sign or Uhthoff syndrome.

This is a condition in which even a minor increase in core body temperature of a quarter of a degree can temporarily worsen a patient's neurological symptoms, causing MS patients to potentially experience enhanced muscle weakness, visual impairment, cognitive problems, imbalance, or even fatigue.

There's a long list of other MS symptoms to look out for since the disease affects everyone differently.

male having eyesight problems and wearing eyeglasses while gazing and reading message on smartphone during breakfast at home. Old man having eye blurred vision indoors.

According to the NMSS, other common symptoms of MS include the MS hug, which is a squeezing sensation around the torso; walking difficulties; numbness or tingling; stiffness; muscle spasms; vision problems; vertigo; dizziness; bladder dysfunction; sexual problems; constipation; loss of bowel control; pain; itching; cognitive changes; emotional changes; and depression. Other MS symptoms that may occur, but are less common among patients include speech problems, loss of taste, swallowing problems, seizures, breathing issues, and hearing loss.

Ultimately though, the disease can show up in different ways for everyone, so if something feels off to you, you should talk to your doctor. "MS symptoms are variable and unpredictable," the NMSS warns. "No two people have exactly the same symptoms, and each person's symptoms can change or fluctuate over time."

RELATED: This Was the First Sign of MS "Sopranos" Star Jamie-Lynn Sigler Noticed.

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