Reporting delay and corrected incidence of multiple sclerosis

Area of Science:

• Epidemiology
• Biostatistics

Background:

• Accurate incidence measurement is crucial for understanding disease trends.
• Reporting delays can significantly distort epidemiological data, necessitating statistical adjustments.

Purpose of the Study:

• To develop and apply statistical models for adjusting multiple sclerosis (MS) incidence data for reporting delays.
• To compare crude and adjusted MS incidence rates.
• To identify trends in MS incidence based on age groups.

Main Methods:

• Application of two statistical models: a delay distribution model and a regression model.
• Utilizing data from the Danish Multiple Sclerosis Registry.
• Incorporating principles from the Cox proportional hazards model for goodness-of-fit assessment with time-dependent and independent covariates.

Main Results:

• The goodness-of-fit analysis indicated the need to analyze age groups (onset <40 and onset ≥40 years) separately.
• Adjusted incidence rates were calculated using estimated delays and their variances.
• Crude and adjusted incidence rates were compared, revealing an increasing trend in MS incidence since 1965, predominantly in the younger age group.

Conclusions:

• Statistical adjustment for reporting delays provides a more accurate estimation of multiple sclerosis incidence.
• The incidence of multiple sclerosis has been increasing since 1965, with a notable rise in individuals under 40 years of age.
• Separate analysis of age groups is essential for robust epidemiological findings in multiple sclerosis.