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Published on: January 11, 2020
Left-censored dementia incidences in estimating cohort effects
Rafael Weißbach1, Yongdai Kim2, Achim Dörre3
1Chair in Statistics and Econometrics, Faculty for Economic and Social Sciences, University of Rostock, 18051, Rostock, Germany. rafael.weissbach@uni-rostock.de.
This study reveals a concerning linear increase in dementia incidence across German birth cohorts. However, accounting for early-diagnosed cases significantly alters this trend, highlighting the impact of left-censoring on dementia risk analysis.
Area of Science:
- Epidemiology
- Biostatistics
- Gerontology
Background:
- Dementia incidence trends are crucial for public health planning.
- Previous analyses may not fully account for left-censored data (individuals diagnosed before the study start).
- Understanding cohort-specific dementia risk is essential.
Purpose of the Study:
- To estimate dementia incidence hazard for German birth cohorts (1900-1954).
- To investigate the impact of left-censoring on dementia incidence trends.
- To analyze age-specific dementia risk patterns.
Main Methods:
- Utilized data from Germany's largest health insurance company (2004-2012).
- Employed a multiplicative hazard model.
- Incorporated uncensored, right-censored, and left-censored dementia cases (N=36,000 + 200,000 + 11,000).
Main Results:
- A positive, linear trend in dementia hazard was initially observed across cohorts.
- Inclusion of left-censored data significantly reduced the trend's slope due to cohort imbalance (Simpson's paradox).
- Age-specific dementia hazard varied when left-censoring was included, suggesting omitted covariates.
Conclusions:
- Left-censoring is critical for accurate dementia incidence estimation and trend analysis.
- Simpson's paradox can mask true cohort effects in dementia research.
- Further research should explore omitted covariates influencing age-specific dementia risk.
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