If you’re exploring your 23andMe Health results for the first time, the sheer amount of information may seem overwhelming. There are nearly 200* reports connecting your genetics to various health conditions and traits. There is an active community of other customers asking and answering questions related to health. And if you love details, there’s also a tool for browsing your raw data — all of the hundreds of thousands of locations in your genome that we’ve determined from your sample.
So where do you start? This is a personal choice, one that is often directed by questions you may already have about diseases that run in the family or that you’re interested in for other reasons. But whether you have a set of health topics in mind or not, it may help to know what 23andMe offers the curious individual. With this series of posts on Health at 23andMe, I’ll lay out the landscape of 23andMe’s health service, dissect different types of health reports, and answer some frequently asked questions, using some of my own results as examples.
Before we get into the details of the different types of health content available to 23andMe customers, it may be helpful to review what exactly 23andMe determines from your saliva sample.
All of us have a genome made up of DNA. DNA itself is made up of individual molecules called nucleotides, which can come in four types designated by the letters ‘A’, ‘G’, ‘T’, and ‘C’. These nucleotide letters are connected together in long, linear sequences of DNA, spelling out genes and other important instructions along the way. Each of our chromosomes consists of such a sequence of DNA, millions of nucleotides in length. And since we have two copies of each chromosome — one from dad and one from mom, except for the X in males — we have two letters at each location in the genome (a “genotype”).
If you compare the sequences of letters between two people, you’ll find that they are over 99% identical. But there are places where the letters might be different. Some of these differences are large — chunks of letters are missing or duplicated, for example — or they can be different at just a single letter location, an ‘AA’ genotype in one person vs. ‘AC’ in another. These single letter differences can be quite common, and what 23andMe does is determine your genotype at hundreds of thousands of these commonly variable sites, called single nucleotide polymorphisms (SNPs).
Researchers have been studying SNPs (pronounced “snips”) and their impact on human health for many years now, and some links are well-established. For example, a number of SNPs located in genes involved in the immune system have been associated with multiple autoimmune conditions such as rheumatoid arthritis and lupus. There are also many SNPs that have been associated with common cancers of the breast and prostate. But for the most part, the effect that each of these SNPs has on disease risk is small — usually modifying risk about 1-2 times compared to average.
23andMe also determines your genotypes for a number of locations where variation is much more rare and having two copies of the rare version has direct implications for disease. These are included in a number of reports under “Carrier Status” category.
Indeed, for those who don’t have specific health topics in mind but wish to explore their health content methodically, 23andMe classifies its health reports into four different categories*, each dealing with a different area of health information:
|Disease Risk. Most diseases are complex, meaning many factors — both genetic and non-genetic — affect whether someone develops the disease. These reports include information on some of the known genetic factors associated with various diseases, and how your own genetics influences your risk. This category includes conditions like Type 2 Diabetes, Prostate Cancer, and Atrial Fibrillation.|
|Inherited Conditions (Carrier Status). Some diseases are directly caused by rare genetic variants — known as mutations in this context — in specific genes. Because two copies of a mutation are usually required to cause the disease, people with one copy usually don’t have the disease, but are called “carriers”. Our reports on Inherited Conditions will tell you whether you carry some of the more common mutations known for certain diseases. This information is especially relevant to individuals planning to have children. This category includes conditions like Cystic Fibrosis, Tay-Sachs Disease, and Sickle Cell Anemia.|
|Drug Response. Different people respond to drugs in different ways, and this is at least partly due to genetics. These reports include information on how your genetics may influence your sensitivity to a drug, risk of side effects, or general effectiveness. This category includes Warfarin Sensitivity, Fluorouracil Toxicity, and Response to Hepatitis C Treatment.|
|Traits. Eye color, hair color, whether you flush when you drink alcohol: these are all familiar things we can easily see or discern. But some traits may not be so familiar — for example, did you know that some people detect a distinct smell in their urine after eating asparagus? (Hint: it has something to do with genetics!) Other reports in this category include Lactose Intolerance, HDL Cholesterol Levels, and Male-Pattern Baldness.|
Other posts in this series walk through results for these different categories and explain how to navigate each type of health report.
* Based on current products and services. Exact details subject to change.