Betula is a longitudinal, prospective cohort-based population study that started in 1988 and aimed to study the relationships between health, aging and memory. Every five years the study participants have been tested again and new cohorts have been included. In total, six test waves (T1-T6) have been conducted until 2014 and six cohorts (S1-S6) have been included. The study is fairly unique with its long follow-up time and scope both in terms of study population and the amount of data collected. The Betula database includes individual data from more than 4,500 people who fulfill the inclusion criteria (the exclusion criteria were severe sensory disability, dementia, intellectual disability, serious mental illness and other mother tongue than Swedish).
At each test occasion, the examination has been divided into two occasions (approximately one week in between) where a health examination constituted the first examination. At the second examination has cognitive functions. Between the first and second test occasions, the study participants filled in a battery of self-assessment forms.
The health examination consisted of a health interview, questionnaire and sampling (Hb, glucose, SR, urine, research samples) and examination of blood pressure, heart rate, height, weight, waist and buttocks, grip strength, vision, hearing, smell etc. which was carried out by nurses according to a special manual. From the health interview and questionnaires, data were collected regarding education level, alcohol habits, smoking, leisure activities, stress, sleep problems, drug use, medical history, family relationships and social relationships.
The project's battery of cognitive tests is extensive and consists of sub-tests that evaluate various memory systems such as episodic memory, semantic memory, working memory, prospective memory and other cognitive functions such as perceptual speed, visuospatial ability and decision making. Mini mental tests (MMT / MMSE) as well as questions for assessing subjective experiences of memory function and experience of memory loss have also been included.
A large number of cross-sectional or longitudinal data have been published over the years on the basis of cognitive and health-related data with the aim of identifying variables that predict age-related cognitive changes and the risk of dementia.