CMT Prevalence Rising in UK, But Patients May Be Living Longer

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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The number of people in the U.K. known to have Charcot-Marie-Tooth disease (CMT) or another neuromuscular disease (NMD) rose by 63% between 2000 and 2019, a study involving almost 13 million people found.

Researchers also observed that while lifetime prevalence — the part of a population given a diagnosis at some point in life — exceeded that of other current estimates, the number of new cases remained constant each year. This suggests that patients are living longer, the researchers noted.

The study, “Prevalence and incidence of neuromuscular conditions in the UK between 2000 and 2019: A retrospective study using primary care data,” was published in the journal PLOS One by a team of researchers at St. George’s Hospital in London.

Knowing how many people have a certain disease is important for healthcare planning as it allows policymakers to understand the burden of that disease on the healthcare system at a given point in time.

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This is of particular importance when it comes to specialized care, such as that required by NMD patients. “In the UK, access to such specialist services, community therapies and social care vary by region, resulting in potential care inequities,” the researchers wrote.

To have an accurate estimate of how many are living with an NMD in the U.K., the researchers searched the Clinical Practice Research Datalink (CPRD) database, an electronic set of primary care data for the country.

“Large-scale electronic primary care datasets can provide up-to-date, accurate epidemiological information on rarer diseases, where specialist diagnoses from hospital discharges and clinic letters are generally well recorded and electronically searchable,” the scientists added.

They looked at both prevalence (total number of cases) and incidence (number of new cases each year) rates from 2000 to 2019. To compare trends over these 20 years, rates were adjusted by age relative to the CPRD population in 2019.

By 2019, the records of 12.6 million patients across the U.K. had been entered into the database.

Of them, 28,230 had been diagnosed with a neuromuscular disease. This amounted to a prevalence rate of 223.6 (NMD’s incidence among every 100,000 people), with males having a higher prevalence (239) than females (208.3). By comparison, the prevalence of NMDs was 136 (per 100,000 people) in 2000.

The prevalence of CMT was 29.5, which was lower than that of Guillain-Barre syndrome (40.1), a rare condition in which the immune system damages the nerves; myasthenia gravis (33.7); and muscular dystrophy (29.5). CMTs prevalence was higher than that of idiopathic inflammatory myopathies (25.0), disorders marked by chronic muscle inflammation and muscle weakness.

Since the start of 2000, the overall prevalence of NMDs rose by 63%, with the greatest increase among adults ages 65 or older. However, overall incidence remained constant.

“The increase in prevalence among older ages suggests increases in life expectancy,” the researchers wrote.

Among all NMDs, CMT showed the greatest increase in prevalence: from 12.3 per 100,000 people in 2000 to 29.5 per 100,000 in 2019. This increase was most evident among children up to age 14 and among adults age 45 and older. The prevalence of CMT in older adults, those 65 and up, “more than tripled from 16.0 to 49.0 per 100,000” over this study’s years, its researchers noted.

“As CMT is associated with a substantial economic burden, it will be important to determine whether these increases we observed in the population are real,” they wrote.

In 2015–19, a total of 8,563 people were diagnosed with some form of an NMD. This represented an estimated rate of 14.1 per 100,000 person-years, and again was higher among males (15.8) than females (12.4).  Person-years is a measure that takes into account both the number of people in a study and the amount of time each person spends in it.

Over these same years, 879 new cases of CMT were reported, representing an estimated rate of 1.44 per 100,000 person-years, and higher among males (1.64) than females (1.25).

“Lifetime recording of many NMDs on primary care records exceed current estimates of people living with these conditions; these are important data for health service and care planning,” the researchers concluded.

“Temporal trends suggest this number is steadily increasing, and while this may partially be due to better recording, it cannot be simply explained by new cases, as incidence remained constant,” they added.