FinnDiane LifeOne Study - Impact of ageing on people with type 1 diabetes, a prospective observational cohort study

IntroductionLife expectancy for people with type 1 diabetes has increased due to improved treatment of diabetes and its comorbidities, allowing many to reach old age. Still, we lack knowledge of how individuals with type 1 diabetes age. On one hand, those who reach older age can be considered survivors, but on the other hand their long-standing diabetes might still exhibit negative impacts on their health and functional ability. Healthy ageing is the World Health Organizations priority for this decade. The focus has shifted from chronological age to functional ability, which reflects the ability of individuals to perform meaningful activities. Functional ability is shaped by intrinsic capacity, the environment, and their interaction. Intrinsic capacity encompasses five main domains: cognition, vitality, sensory function, locomotion, and psychological domain. This observational study aims to assess how this vulnerable group of individuals with type 1 diabetes age and to identify factors that contribute to their healthy ageing, intrinsic capacity, and its domains. Methods and analysisThe FinnDiane LifeOne Study is a prospective observational cohort study. We aim to recruit a minimum of 300 individuals with type 1 diabetes from the FinnDiane Study, aged >65, and a minimum of 100 matched controls without insulin-dependent diabetes. The cohort will be comprehensively characterized, including clinical assessment, laboratory tests, questionnaires, and a geriatric assessment of different aspects of functioning ability, with five years intervals. We will compare the individuals with type 1 diabetes to their matched controls. For those with type 1 diabetes, we will further assess which factors from the FinnDiane baseline and trajectories during follow-up predict healthy ageing in above 65-year-olds. Ethics and disseminationThe LifeOne study protocol is approved by the Ethics Committee of HUS Helsinki University Hospital (HUS/4387/2023) and the study adheres to the Declaration of Helsinki. Written informed consent is obtained from each participant. Findings will be published in international peer-reviewed journals with an open access choice. The study is registered at ClinicalTrials.gov with ID NCT07289204. STRENGTHS AND LIMITATIONS OF THE STUDYO_LIThis is a prospective observational cohort study with a matched control group. C_LIO_LIFor the participants with type 1 diabetes, we have unique and comprehensive longitudinal clinical and genetic data available from approximately participants middle age, enabling identification of factors that contribute to their healthy ageing, while accounting for the competing risk of death. C_LIO_LIThe cohort is thoroughly characterised regarding diabetes, cardiometabolic health, lifestyle, psychosocial factors, and includes a geriatric assessment, thereby enabling comparison of impact of ageing between individuals with type 1 diabetes and controls without insulin-dependent diabetes. C_LIO_LIThe cohort is Caucasian with recruitment from Southern Finland, potentially limiting generalisability to other more ethnically diverse populations. C_LI