Description: A recent study sheds light on the measurement and implications of the relationship between increased morbidity and declining disability. The results were not consistent across all populations. This study of the compression of morbidity is part of a wider project called the M-project, led by the four authors, which aims to explore the demographic factors leading to an increase in the adult longevity, investigate the phenomenon called the compression of mortality and develop a new methodological approach to longevity analysis with focus on the modal age at death M.