Understanding more about how diseases that cause dementia develop is critical as the number of people living with, or affected by, dementia in Scotland continues to grow. The IONA Longitudinal Cohort Study (LCS) has been set up to gather information about people's cognitive health (their memory and thinking abilities), their lifestyle and health risk factors for future dementia (such as hearing loss and obesity), genetics and disease biomarkers, over a number of years. The IONA LCS has three main objectives: Firstly to develop this cohort that is well characterised (also known as being well-phenotyped) that represent the Scottish population (taking into consideration age, sex, ethnicity and education). The second objective is to use this data to build disease models to better understand trajectories of diseases, and identify any sub-populations who have different (i.e. better, worse) disease trajectories. Finally the third objective for IONA LCS is to offer people an optional consent to hear about future studies they may be interested in taking part in.