Experts have uncovered the lifestyle factors that lead to the development of Multiple Sclerosis (MS), a devastating neurological disease that has no cure and affects 2.8 million people worldwide.
For decades, primarily young adults carrying the MS gene were diagnosed with the condition. But recently, there has been an alarming rise in MS diagnoses in seemingly healthy adults in their midlife.
Highlights
- Researchers have revealed several lifestyle and environmental factors that can cause Multiple Sclerosis.
- Actresses Christina Applegate and Selma Blair are among those whose lives and careers were disrupted by the illness.
- Among the factors are a habit that 9.9% of Americans have, and an infection that plagues 95% of Americans.
Hollywood’s Christina Applegate and Selma Blair learning to walk with canes in their 50s, or hearing journalist Tom King talk about his diagnosis at 62, are grim reminders of that reality.
“Developing MS is not a one-hit type of thing,” said Dr. Erin Longbrake, a neurologist specializing in MS. “It's all of the little pebbles being added onto the scale, and it finally tips over into disease.”
Christina Applegate’s life turned upside down with an MS diagnosis at 49
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Christina Applegate had spent decades as one of Hollywood's most recognizable actresses, rising to fame as Kelly Bundy on Married... with Children before earning critical acclaim and Emmy nominations for her roles in Samantha Who? and Netflix's Dead to Me.
Even after overcoming breast cancer in 2008 with a double mastectomy, she continued working steadily, balancing a successful acting career with motherhood.
Everything changed in 2021 when, while filming the final season of Dead to Me, she was diagnosed with MS.
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Applegate has said she initially noticed subtle symptoms, including problems with balance, numbness in her limbs, and subtle tingling in her toes, but attributed them to fatigue before learning the devastating truth.
The disease progressed rapidly. Soon, her symptoms progressed to debilitating leg weakness, intense neuropathic pain, gastrointestinal distress, and vision problems.
Although she has since spoken candidly about her experience and advocated for MS awareness, the Bad Moms actress has also acknowledged the grief of watching her physical abilities and her acting career gradually slip away.
“Where am I with acceptance? Not at all. I hate it,” she said about her diagnosis on Good Morning America in March 2026.
Image credits: Voyagerix/Adobe Stock (Not the actual photo)
A study in Italy found that MS diagnosis in adults in their 60s more than tripled between 2005 and 2020. MS cases among adults aged 50 or older increased from 2.6% before 1970 to nearly 12% after 2010 in a Norwegian study.
While some researchers believe the statistics are due to advances in diagnostic technology or an ever-aging population, most disagree.
“Improved diagnosis is probably not the whole explanation,” UK-based Neurologist Dr. Rab Nawaz Khan told the Daily Mail. “The trend is real — but we cannot point to one proven reason. It's likely that a combination of factors is at play.”
MS-specific studies, including one published in February 2026 on PubMed Central, say that low sun exposure, Vitamin D deficiency, using tobacco, lack of exercise, and obesity are some of the leading causes of MS onset.
A 2019 study also listed overconsumption of coffee, al**hol, and oral tobacco, as well as night-time work, as potential triggers.
Actress Selma Blair drank and used tobacco for years before her MS diagnosis
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Debuting in 1995, Selma Blair built a successful Hollywood career with memorable roles in films like Cruel Intentions, Legally Blonde, and Hellboy.
Behind the scenes, Selma Blair was battling unexplained symptoms since childhood. She experienced chronic pain, numbness, fatigue, and balance problems that were repeatedly dismissed or misdiagnosed.
In her memoir Mean Baby, she said she drank to cope with the physical pain and distress before getting sober in her 30s.
Sometime in 1998, an eye doctor suggested she get herself checked for MS after finding an inflammation in her optic nerves. She brushed it off.
Image credits: Kaspars Grinvalds/Adobe Stock (Not the actual photo)
In 2018, after years of worsening health, Blair was finally diagnosed with multiple sclerosis at age 46. By then, she was struggling with severe muscle spasms, difficulty walking, tremors, chronic pain, cognitive issues, and overwhelming exhaustion.
She has spoken openly about falling frequently, dropping objects, and feeling as though her body was betraying her. She has also talked about quitting tobacco, a vice she maintained for 20 years before her diagnosis, and using nicotine patches instead.
Tobacco happens to be one of the most widely studied factors for MS, and the one habit that seemingly has the biggest influence on MS development.
Research shows that tobacco users are 50% more likely to develop MS than those who don’t, and some studies put the risk percentage even higher, up to nearly double. The more a person smokes, the greater their risk, and those who start young are especially vulnerable.
“Avoiding tobacco cig**ettes is probably the best lifestyle factor and the most important one for lowering your risk of developing MS,” Dr. Michael Kornberg, a neurologist at Johns Hopkins, told the Daily Mail.
A 2022 study published in Frontiers in Immunology compared more than 9,400 MS patients with healthy individuals and found that 44% of the former group were tobacco users, compared with 46% in the latter group. The study concluded that at least 13% of MS cases could be prevented if people avoided tobacco entirely.
The threat extends to those who are passively exposed to it. A Swedish study found that those who were regularly exposed to passive smoke had a 30% higher chance of developing MS compared to those with no exposure.
Health issues affecting a large percentage of Americans have also been linked to MS
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While tobacco is an avoidable choice, contracting mono is not, and the latter remains the strongest-known environmental risk factor for MS.
Mononucleosis, a viral infection caused by the Epstein-Barr virus (EBV), is contracted by about 95% of Americans by the age of 40.
A study found that people infected with EBV were 32 times more likely to develop MS than those who remained uninfected.
More than 99% of people who have MS tested positive for EBV antibodies. In most cases, the infection appeared in the blood about five years before they were diagnosed with MS.
Image credits: Ernst-Günther Krause (NID)/Pexels (Not the actual photo)
“Humans have co-evolved with EBV for a long time, so there are still unknowns as far as what happens if you vaccinate against it,” Dr. Longbrake told the Daily Mail. “We don't know if there might be unintended consequences, but vaccines are being developed.”
According to experts, spending too much time indoors, excessive sunscreen use, and living in northern regions with limited sunlight can also lead to MS in adults.
Unlike most other nutrients, the human body cannot absorb Vitamin D from food but rather absorbs it from the sun’s ultraviolet (UV) rays through the skin. A 2022 study found that nearly two-thirds (around 40%) of Americans have Vitamin D Deficiency (VDD), with 2.6% being severely deficient.
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The absence of Vitamin D, which helps the body absorb calcium, can cause muscle and bone pain, persistent fatigue, and a weakened immune response. Low Vitamin D levels may also weaken the blood-brain barrier, making it easier for rogue immune cells to enter the central nervous system.
“MS patients are usually deficient in vitamin D, and that may have to do with their sun exposure,” Dr. Longbrake told the Daily Mail.
The outlet reported a meta-analysis of 14 studies on the matter, which determined that people with VDD had a 54% higher risk of developing MS than those with sufficient levels.
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