The aim of this thesis is to shed light upon the association between body mass index and plasma triglycerides and risk of dementia. Two original articles are discussed in relation to the existing literature in the form of a review. In the first article we investigated the association between body mass index and risk of Alzheimer’s disease using a Mendelian randomization study design. In the second study we investigated the association between plasma triglyceride concentration and risk of non-Alzheimer dementia, Alzheimer’s disease, and ischemic stroke.

In observational analyses we found low body mass index to be associated with high risk of Alzheimer’s disease, but we found no association between genetically predicted low body mass index and risk of Alzheimer’s disease. Observationally, high plasma triglycerides associated with high risk of developing non-Alzheimer dementia and ischemic stroke.

In conclusion, the association between low body mass index and high risk of Alzheimer’s disease is likely to be due to reverse causation. To determine whether the association between high plasma triglycerides and risk of non-Alzheimer dementia is of a causal nature future Mendelian randomization studies will be necessary.