Trends in population health in an era of increasing longevity

Abstract

In Sweden, the number of older adults over the age of 85 increased by 75% since 1990 while the number of centenarians has almost quadrupled. Rapid population ageing is a global phenomenon and projected to continue in almost all countries worldwide, Sweden among them, throughout the 21st century. Since old age is generally associated with a high risk of disease and care-dependency, population ageing often evokes concern. However, population ageing is accompanied by changing disease patterns and by a changing sociodemographic population composition and its consequences for public health are thus not straightforward.

Highlighting heterogeneity in the population, this thesis aims to present changing mortality and morbidity patterns among older adults in Sweden during the past three decades. I thereby aim to increase the understanding of changing health and geriatric care needs in an ageing society and to explore how a changing population structure affects population health. The thesis is based on a linkage of several nationwide population registers covering all individuals over the age of 60 in Sweden. It integrates both epidemiological and demographical methods and focuses on some of the most common and severe diseases in old age. While Studies I and II additionally include cardiovascular diseases and cancer, the two most common causes of death globally, Studies III to V focus on hip fractures – an enormous public health issue in Sweden, where lifetime risks exceed 20% among women and 10% among men.

In Studies I and II, we use life table methods and decomposition techniques to show that remaining life expectancy in old age has increased faster among men and women with a history of cardiovascular diseases and cancer than it has in the general population. Almost half of the total increase in Swedish life expectancy during 1994 to 2016 can be attributed to improved survival among individuals with a history of myocardial infarction alone. As a result of longer life expectancy, disease prevalence increased. These two processes had counteracting influences on the development of life expectancy, but at least for cardiovascular diseases, the positive impact of improved survival far outweighed the negative one caused by rising disease prevalence. In contrast to all other diseases, life expectancy did not increase among older adults with a history of hip fracture.

In Study III, we found the Swedish Hip Fracture Quality Register and National Patient Register to be suitable to study nationwide hip fracture trends. Nevertheless, some patients dying shortly after their fracture were not included in the quality register, indicating a selection towards healthier patients. We further derive algorithms to operationalize first and recurrent hip fractures in the National Patient Register. Study IV shows that the age-standardized incidence of first and recurrent hip fracture has declined between 1998 and 2017 in the total population and in population strata defined by gender, education, comorbidity level, and birth country. Nevertheless, 20% of women and 30% of men died within one year of their first hip fracture and these risks remained essentially unchanged. The lack of mortality improvements could at least partly be attributed to rising comorbidity levels among hip fracture patients.

Study V demonstrates that hip fractures have an immediate negative impact on care trajectories of older patients. However, already before their fracture, older adults who sustained a hip fracture were frailer and more likely to receive geriatric care than the general older population. Our comparison to a health-matched control group suggests that the increase in care use among hip fracture patients might have also occurred in absence of the fracture, even if somewhat later.

In conclusion, life expectancy increases were not limited to the healthy part of the population. Rising life expectancy can at least partly be attributed to tertiary prevention enabling older adults who experienced severe diseases to survive longer. However, trends were not uniform across diseases. While we observed rising life expectancy among older adults with a history of cardiovascular diseases and cancer, hip fracture patients – and especially men – remain a vulnerable population group with increasing comorbidity levels and high mortality risk. Our findings also emphasize the importance of selection processes and the choice of adequate comparison groups when examining the consequences of disease.