12-month survival in nonagenarians inside the Mugello study: on the way to live a century

Background: Life expectancy has increased over the last century and a growing number of people is reaching age 90 years and over. However, data on nonagenarians' health trends are scarce due to difficulties in investigating this specific population. This study aims to identify risk factors for one-year mortality in nonagenarians using data collected within the "Mugello Study". Methods: Complete information on sociodemographic data, cognitive and functional status, lifestyle, medical history, and drug use was collected from 433 nonagenarians, as well as information about survival after 1 year from the interview. Results: The sample included 314 women (72.5%) and 119 men (27.5%) with a median age of 92 years (range 90-99 years). The mortality rate was 20.3% (88 deaths). After adjustment for age and sex, a significantly higher risk of dying within 12 months was observed in individuals with more severe cognitive impairment (HR = 5.011, p < 0.001), more severe disability in basic activities of daily living (HR = 4.193, p < 0.001), sedentary lifestyle (HR = 3.367, p < 0.001), higher number of drugs assumed (HR = 1.118, p = 0.031), and kidney dysfunction (HR = 2.609, p = 0.004). When all the variables were included in the analysis, only older age (HR = 1.079, p = 0.048), lower cognitive function (HR = 2.859, p = 0.015), sedentary lifestyle (HR = 2.030, p = 0.026), and kidney dysfunction (HR = 2.322, p = 0.018) remained significantly associated with reduced survival. Conclusions: Data from the Mugello study support the hypothesis that survival at 12 months in nonagenarians is not a stochastic process and that older age, reduced cognitive function, sedentary lifestyle, and the presence of kidney dysfunction are associated with mortality.