Causes of Death Among 9000 Danish Centenarians and Semisuper-Centenarians in the 1970–2012 Period

As most centenarians suffer from multiple diseases, they are at high risk of dying – but what do they ultimately die of? This question has scarcely been examined. We have carried out a register-based study of the causes of death (CoD) among Danish centenarians. Among 8559 centenarian deaths in the 1970–2012 period, the most common CoD was in the category of cardio- and cerebrovascular diseases (CVD); at the end of the study period, this CoD accounted for one-third of the deaths in this age group. The mortality rate for CVD as an underlying CoD was more than halved during the period (from 358 to 170 per 1000 person-years). In contrast, the mortality rate for cancer remained stable during the whole period, but at a very low level (15–20 per 1000 person-years). Cancer made up a much smaller share of underlying CoDs among this age group (3–4%) than among 85–99-year-olds (15%). The mortality rate for pneumonia remained at a constant level (about 50 per 1000 person-years) of around 10% among centenarians and 5% among 85–99-year-olds. The underlying CoD groups that were reported with increasing frequency during the period were mental diseases, including dementia, which increased sevenfold; and ill-defined conditions/senility, which increased fourfold. The latter CoD group accounted for 28% of deaths among centenarians in the most recent years, and for more than one-third of deaths among semi-supercentenarians (aged 105–109). The increase in the proportion of deaths for which the CoD was listed as ill-defined conditions/senility was probably partly due to the under-diagnosis of diseases among centenarians, especially of heart diseases. However, a substantial proportion of these deaths may have been attributable to “old age” – i.e., a combination of several diseases and organ deficiencies – and not to a single underlying cause.