Compression and Expansion of Morbidity­Secular Trends Among Cohorts of the Same Age

BACKGROUND: Morbidity is said to be compressed when the interval from the onset of a disease or disability to death becomes shorter over time, or when the incidence of the disease or disability declines over time. In the reverse situation, morbidity is said to be expanded. METHODS: This review is based on national and international studies retrieved by a selective literature search on secular trends in morbidity and mortality. The findings were derived from data from surveys and registries, and from the routine data of health insurance carriers. RESULTS: Three different types of secular trends in morbidity were seen. For some diseases (e.g., lung cancer, stroke, and dementia), morbidity among the elderly was compressed over time. On the other hand, for multimorbidity and type 2 diabetes including comorbidities, morbidity expanded over time. Unexpectedly, a double development was seen in certain other conditions, with both compression among the elderly and expansion among the middle-aged: this was particularly so for myo - cardial infarction, grip strength, and indicators of general health. CONCLUSION: The notion of morbidity being reduced by compression seems less tenable in view of the double development just mentioned. The findings suggest that the observed secular trend toward better health among the elderly has not persisted among the more recently born cohorts. This can have negative effects on social security systems, particularly with respect to retirement ages being deferred or made more flexible, as well as the cost of health care.