Related Experiment Video
Updated: May 10, 2026

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data
Published on: December 9, 2015
Observation period effects on estimation of systemic lupus erythematosus incidence and prevalence in Quebec
Ryan Ng1, Sasha Bernatsky, Elham Rahme
1Division of Clinical Epidemiology, McGill University Health Centre (MUHC), Montreal, Quebec, Canada.
Objective:
To determine how duration of observation affects estimation of incidence and prevalence of systemic lupus erythematosus (SLE).
Methods:
SLE incidence and prevalence estimates from data periods as brief as 3 years (2001-2003) were compared to estimates from a 15-year period (1989-2003).
Results:
The 15-year period incidence was 5.6/100,000 (95% CI 5.0-6.1) and the prevalence was 59.1/100,000 (95% CI 57.4-60.8). When a 3-year period was used, incidence was overestimated by 238.1% and prevalence underestimated by 66.0%.
Conclusion:
SLE incidence and prevalence estimates vary considerably according to the observation period; more than 5 years of data is likely required.
Related Concept Videos
Prevalence and Incidence
Prevalence indicates the proportion of individuals in a population who have a specific disease or health condition at a...
Observational Studies
There are three types of observational studies – Prospective, retrospective, and cross-sectional.
Prospective Study
Prospective studies, also known as longitudinal or cohort studies, are carried out by collecting future data from groups sharing similar characteristics. One example of...
Steps in Outbreak Investigation
Data Collection by Observations
An astronomer viewing the motion and brightness of stars in the sky and recording the data is an example of observational data collection. A botanist recording...
Assumptions of Survival Analysis
Statistical Methods for Analyzing Epidemiological Data
