Population genetic history

The Finnish population structure offers a unique setting for discovering genetic associations with diseases. The Finnish population has a history of geographic and cultural isolation followed by rapid expansion. The significant isolation and a series of population bottlenecks, particularly during harsh climatic conditions and famines, shaped the genetic structure of the Finnish people.

Owing to a founding genetic bottleneck and long-lasting isolation enforced by geography and language, Finland has an unusual enrichment of specific functionally relevant low-frequency alleles compared to other European populations. This enables the identification of disease-causing variants much more readily than in most populations in the world. 

Due to its historical isolation and relatively recent expansion from a small founder population, Finland exhibits a high degree of genetic homogeneity. This means that many Finns share a larger number of genetic markers compared to more heterogeneous populations.

The genetic homogeneity of the Finnish population makes it easier to study complex genetic diseases. This is because there are fewer genetic variations to consider when associating a particular genetic change with a disease.

A strong founding bottleneck ~120 generations ago causes some strongly deleterious genetic variants to be considerably more common in Finland than expected, meaning that identifying such variants is dramatically easier in medical genetics research. This facilitates the identification of rare or low frequency variants in both previously identified genetic risk loci and the discovery of novel risk loci. Due to the same bottleneck phenomenon, these deleterious variants are seen in many individuals in the population.

Furthermore, it is well established that imputation-based reconstruction of whole-genomes works substantially better in founder populations, suggesting that in Finland it is more easily and inexpensively possible to  reach down to very rare frequencies via such methods than in more heterogeneous populations. 

Although generally homogeneous, there are slight genetic differences between people from different regions of Finland, largely due to historical settlement patterns and slight variances in the small founding populations of these regions.