In 2009, the average life expectancy of Canadians was 81 years with females living on average longer than males (83 years vs. 79 years respectively). Most people would agree that diet, exercise and smoking status are some of the biggest determinants of how long you will live, but what about genetics? Some studies have shown that survival into the 9th decade of your life is up to 25% due to your genetics and that genetics becomes more important in cases of extreme longevity (EL, people living longer than 100 years). It has been shown that siblings of centenarians have up to a 17 times greater chance of also living to or beyond 100 than people whose siblings are not centenarians. So the question then is which genes are important in determining whether you will live beyond a century?
There have been a number of studies looking into this over the years and they have identified variants in three genes that appear to be present in people who have EL. Variants (called single nucleotide polymorphisms or SNPs) are subtle changes in a gene that changes the way the protein it codes for functions (again subtly). This video describes SNPs well. Sometimes this is a bad change; there are many SNPs that are associated with increased risk for diseases. Sometimes these are good changes and, in this case, are associated with increased longevity. Many probably have never heard of the genes linked to longevity but I will give a brief summary of the genes and their function (consider it your biology lesson for the week):
- FOXO3A – Also known as Forkhead box O3 (what now?). This protein is thought to be important in ensuring the production of natural anti-oxidants in the body and coordinating cell suicide (apoptosis), which is important in preventing things such as cancer or ensuring your fingers and toes develop normally. More anti-oxidants and prevention of cancer makes sense with increased longevity.
- APOE – Also known as Apolipoprotein E. This protein is responsible for forming ‘bubbles’ that are responsible for removing excess cholesterol from the blood and taking it to the liver for processing and/or removal. Certain mutations in the gene have been linked to disorders like Alzheimer’s and atherosclerosis (or hardening of the arteries). Better control of cholesterol would lead to less chance of heart or neurological disorders and therefore increased longevity.
- APOB – Another Apolipoprotein (in this case B). This protein is necessary for the ‘bubbles’ that carry cholesterol (and other fats) to bind to cells in the liver or throughout the body and deposit their fats at the cell. Without this functioning correctly, people can have problems with either too much cholesterol in their blood or too little. Again, cholesterol control.
It is apparent from these studies so far that proper cholesterol transport and regulation in the blood is important in determining longevity. More research needs to be done to determine the exact relationship between cholesterol and longevity, although it is likely that it has something to do with heart disease or hardening of the arteries. It will be interesting in the future to see if certain populations are more likely to have these variants and therefore are more likely to live longer. You may not have these variants in your family but you can ensure you live to at least the average or longer if you get your cholesterol levels under control, exercise, quit smoking, eat well and keep your heart healthy.