{'fraction_non_alphanumeric': 0.012514220705346985, 'fraction_numerical': 0.0, 'mean_word_length': 5.3768115942028984, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Random Changepoint Model for Joint Modeling of Cognitive Decline and Dementia

Summary We propose a joint model for cognitive decline and risk of dementia to describe the pre‐diagnosis phase of dementia. We aim to estimate the time when the cognitive evolution of subjects in the pre‐dementia phase becomes distinguishable from normal evolution and to study whether the shape of cognitive decline depends on educational level. The model combines a piecewise polynomial mixed model with a random changepoint for the evolution of the cognitive test and a log‐normal model depending on the random changepoint for the time to dementia. Parameters are estimated by maximum likelihood using a Newton–Raphson‐like algorithm. The expected cognitive evolution given age to dementia is then derived and the marginal distribution of dementia is estimated to check the log‐normal assumption.