In our studies we focus first on longevity—length of life. Many studies of well-being are flawed because they rely too heavily on participants' answers to queries about their health and wellness—called their "self-report." Their self-reported answers are subjective and often inaccurate. Longevity is not distorted by self-report. Although there is a field of study on the reliability of death certificates, it is pretty much the case that if your death certificate says that you died on April 26, 1989, then we can be reasonably certain of your longevity and of your state of health on that date. Lucille Ball was not a participant in Dr. Terman's studies, but, as we shall see, one of her closest associates was.
Many common beliefs about health and longevity come from a host of biased sources—with distortions that go well beyond the self-report biases. Aside from the self-interest research biases we hear so much about (in which someone has a financial stake in the findings), there are also many sources of inadvertent skew or error. If you think about it—as we do every day in our laboratory—you come to realize that we can never be quite sure about the validity of many health studies and claims.
Of course we can study individuals who stay healthy, but to whom do we compare them? If we knew that two people started out exactly the same at birth but one ate only broccoli while the other ate only fried steak, then we might have a reasonable comparison. But almost all epidemiological studies, even those making daily headlines, compare people who differ in many, many ways. Indeed they differ in ways we cannot know about. Most comparisons of vegetarians and cheeseburger addicts, or of pill-takers and the pill-averse, therefore are necessarily somewhat flawed. The researchers generally do their best to be as accurate as possible, but there are always limits in a complex study of human health. And the statistics that emerge from the studies can be interpreted in many different ways.
One of the best ways to avoid research traps and biases is to follow individuals for their whole lives and see which characteristics influence subsequent qualities, behaviors, and outcomes. What exactly causes people with similar backgrounds to diverge in terms of their health and well-being? This step-by-step procedure is exactly what we have done, and this book is the first comprehensive report of the findings.
Tracing the lives of hundreds of individuals, we have discovered new twists to common health recommendations, such as when staying single or getting divorced can be healthy for women. Our studies have uncovered a series of what we call dead-end myths—common advice that is not supported by good science and can lead to dead ends in more than one sense of the term. Throughout this book, we'll explain exactly why the following common beliefs, to name a few, are false: