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Myasthenia gravis: a changing pattern of incidence
I Casetta1, E Groppo, R De Gennaro
1Section of Clinical Neurology, Department of Medical and Surgical Sciences of Communication and Behavior, Neuroscience Center, University of Ferrara, Corso della Giovecca 203, 44100, Ferrara, Italy. cti@unife.it
Abstract:
The annual incidence of myasthenia gravis (MG) ranges from 3 to 30 per 1,000,000 people. Since the mid-1980s, an increasing incidence has been reported, mainly due to late-onset MG. Whether the increase was due to population aging, improved diagnosis and case collection, or a true excess of incidence cases is still under debate. We used a complete enumeration approach by reviewing all possible sources of case collection in the province of Ferrara, Italy, to estimate the MG incidence and its temporal trend over the study period (1985-2007). The mean annual age-adjusted incidence of MG was 18 per 1,000,000, without any significant temporal trend. The incidence rates in the period 1985-1990 were 14 both for early and late-onset MG. Thereafter, a significant increase in incidence of late-onset MG (p < 0.05), and a decrease in early onset MG were detected (p < 0.01). These findings were related to nonthymoma MG. The median age at onset of the disease steadily increased over time. A changing pattern of MG incidence with an increase in frequency of late-onset and a decrease of early onset MG was found in the last years, giving a significant shift to older age at onset of the disease. Unknown environmental factors may have driven this change in MG epidemiology.
Insights
Myasthenia gravis (MG) incidence shows a shift towards later onset, with increasing late-onset cases and decreasing early-onset cases. This epidemiological change in MG may be influenced by unidentified environmental factors.
Area of Science:
- Neurology
- Epidemiology
Background:
- Myasthenia gravis (MG) incidence has been reported to be increasing since the mid-1980s, primarily due to late-onset cases.
- The reasons for this increase, whether population aging, improved diagnostics, or a true rise in incidence, remain debated.
Purpose of the Study:
- To estimate the incidence and temporal trends of myasthenia gravis (MG) in the province of Ferrara, Italy, from 1985 to 2007.
- To investigate changes in the age of onset for MG over time.
Main Methods:
- A complete enumeration approach was employed, reviewing all case sources in Ferrara, Italy.
- Age-adjusted incidence rates were calculated and analyzed for temporal trends.
- Incidence rates for early-onset and late-onset MG were compared over different periods.
Main Results:
- The mean annual age-adjusted MG incidence was 18 per 1,000,000, with no overall significant temporal trend.
- While early-onset MG incidence decreased (p < 0.01), late-onset MG incidence significantly increased (p < 0.05) after 1990.
- The median age at disease onset steadily increased over the study period, particularly for nonthymoma MG.
Conclusions:
- A significant shift in MG epidemiology towards later onset has occurred, characterized by an increasing frequency of late-onset MG and a decreasing frequency of early-onset MG.
- This changing pattern suggests potential influence from unknown environmental factors impacting MG epidemiology.
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