Living Longer (continued) – How About My Good Genes?

How often have you heard people talking about a grandparent or great grandparent living to be over 100 years old?  It seems almost like a badge of honor to have a relative who passed that hurdle, although in many cases they were alive but no longer had their wits about them. 

Not only is it a matter of pride, it also seems to be somewhat reassuring, especially in the cases where the relative smoked or drank throughout his or her life. People figure that if Aunt Polly lived to 102, it was good news for them.

For a while the nature-or-nurture question was considered a toss up. Do we live longer because of our habits, because of our genes, or is it some combination of the two? Several sets of studies on twins raised in different households tried to find out.

Results from hundreds of individual studies have been published since the early-1980’s showing that genetics, rather than upbringing held sway for many characteristics. “Minnesota researchers found that about 70 percent of IQ variation across the twin population was due to genetic differences.” In other studies genes played a larger role than environment on personality, sexual orientation as an adult, religiosity and social attitudes. 

One of the earliest and most widely publicized stories of identical twins came from a study by Lewis and Springer. One pair of twins separated just four weeks after birth and reunited  39 years later was found to have remarkable similarities. “They both had childhood dogs named Toy, married and divorced women named Linda and then married women named Betty, drove Chevys, had nearly identical smoking brands and drinking patterns, and chewed their fingernails.” Physically, they had similar problems with headaches, and they chose the same Florida beach for vacations.

Soon many people were convinced that nature, that is genes, was a driving force and could be credited or blamed for any number of good and bad outcomes. But not so fast! Leave it to science to mess up a good story.

A study specifically looking into the link with longevity published in Nature several years ago has come back into the spotlight recently. Their primary conclusion was that “genetic differences account for about a quarter of the variance in adult human lifespan.” The advantage they had in studying longevity as oppose to other traits was that they could look at the records of twins over the last 100 years with no need for observation or interviews.

Harvard conducted another study on longevity with 268 students (not twins) beginning in 1938. With almost 80 years of data available, they concluded that “how happy we are in our relationships has a powerful influence on our health,” more powerful than genes alone.

So whether a grandmother or a great aunt lived beyond the normal lifespan seems to have much less effect on individual longevity than previously thought.  (That’s good news for a couple of men I know who have already lived past the age when their fathers died, and are very grateful – that’s perspective.) 

Having ruled out yet another potential factor in the search for long life, where does it leave us? More on this next time.