Next Generation Sequencing (NGS) is just a fancy term for super fast genome sequencing. The first generation was Sanger Sequencing, in which elongating DNA strands were terminated when a specific base showed up. Basically, the same elongating DNA strand would be placed in four separate reactions, each meant to terminate when a specific base appeared (A, G, C, or T). Then, the entire sequence could be visualized either by running each reaction side-by-side on a gel or adding a radioactive label for a computer to read. This process takes a long time, and while still used today, is generally used as a backup for Next-Gen sequencing or for smaller genomes. Next Gen sequencing is much faster. A human genome can be sequenced in a matter of days. A human genome can be sequenced simultaneously with a bunch of other human genomes to gain more information about a specific population (say, people who live in a specific geographic region) in a matter of days to weeks.

Genome-wide association studies (GWAS) are where NGS really becomes relevant to epidemiology. Researchers can look across the entire genomes of multiple individuals to determine if there is an association between a specific gene variant and a specific trait. For example, it can be used to determine if a particular mutation is found in individuals with a specific disease more than it is found in those who do not have that disease.

The first successful GWAS was published in Science in 2005. It investigated the genetic associations with age-related macular degeneration, and found that two single-nucleotide polymorphisms (single-nucleotide variations found consistently among a number of people) that were present in individuals with age-related macular degeneration but not in healthy controls.1

There are, of course, challenges in these kinds of studies. When dealing with genetics - especially entire genomes - the study methodology must be as close to flawless as humanly possible. Extreme care has to be taken when interpreting statistical analyses. Even when an association has been determined by a GWAS, further, less theoretical research should be carried out to investigate the biological plausibility of an association. Although there may be an association with a particular SNP with a disease, that does not necessarily mean that the identified SNP is causally related to that disease. Still, GWAS with all its speed and power looks to me like the future of genetic epidemiology.

1. Klein, Robert J. et al. “Complement Factor H Polymorphism in Age-Related Macular Degeneration.” Science (New York, N.Y.) 308.5720 (2005): 385–389. PMC. Web.