The main objective of the present work is to establish a firm knowledge base regarding depression and anxiety as risk factors for dementia and how social relationships impact this association. This risk factors, and efforts to reduce them are described through a follow up over three decades.

The Health Study in Nord-Trondelag (HUNT) fulfils most of the key requirements of a population-representative cohort study by meeting the following elements: firm knowledge about the population denominator, knowledge about reasons for refusal (in line with previous methods in HUNT), options for levels and localisation of participation (at test station, at home, at nursing homes), coverage of sociodemographic features by the comprehensive HUNT4-protocol and register linkage, inclusion of institutionalized individuals and individuals with reduced capacity to consent, measurement of risk and compensatory factors across the life course by merging with previous results in HUNT surveys and linkage to registries, core elements and assessment methods can be compared with other European populations studies including elderly people, and finally, the ability to include biobank results in the data analysis. The HUNT data supplemented by register linkage include all established and suspected risk factors of dementia.

A particular focus on primary health care is appropriate because it is in this part of the health care system that the need for extra resources due to the substantial increase in dementia prevalence is most pronounced. Furthermore, preventive measures in a life-course perspective will mainly have to be implemented in the primary health care setting.

Inclusion Criteria:

• Living in designated area

Exclusion Criteria:

• None

Inhabitants living in the designated areas that voluntared to the health survey and accepted a cognitive test.