Long before the age of gene therapy and miracle medical treatments, the secrets of long life were being gathered and revealed in a unique study of 1,500 children born about 1910. By studying these people throughout their lives, successive generations of researchers collected nearly 10 million pieces of observable data and have been able to produce solid insights into human longevity.
"Most people who live to an old age do so not because they have beaten cancer, heart disease, diabetes, or lung disease; rather, the long-lived have mostly avoided serious ailments altogether," according to Howard S. Friedman and Leslie R. Martin, in their recent book, "The Longevity Project."
"The best childhood personality predictor of longevity was conscientiousness—the qualities of a prudent, persistent, well organized person," according to the two professors (he at the University of California—Riverside, and she at La Sierra University). "Conscientiousness . . . also turned out to be the best personality predictor of long life when measured in adulthood."
Their book chronicles research begun in 1921 by Lewis Terman, a Stanford University psychologist who selected 1,500 bright and generally high performing children and began amassing detailed information about their personal histories, health, activities, beliefs, attitudes, families, and other variables.
Over the next eight decades, other academics maintained the Terman Project and assembled exhaustive details on all facets of the original subjects' later lives. It is this unique depth of detail that has permitted Friedman and Martin to reach what they feel are scientifically sound conclusions about what it takes to live a long life.
"It was not cheerfulness and it was not having a sociable personality that predicted long life across the many ensuing decades," they wrote. "Certain other factors were also relevant, but the prudent, dependable children lived the longest. The strength of this finding was unexpected, but it proved to be a very important and enduring one."
The book presents three reasons why conscientious people live longer:
1. They are more likely to obey the rules, protecting their health, and not engaging in risky behaviors such as smoking or driving without a seat belt. If a doctor tells them to take a medicine, they take every prescribed dose.
2. "Conscientious individuals are less prone to a whole host of diseases, not just those caused by dangerous habits," they found. "It appears likely that conscientious and unconscientious people have different levels of certain chemicals in their brains."
3. "The most intriguing reason conscientious people live longer is that having a conscientious personality leads you into healthier situations and relationships," the research concluded. "They find their way to happier marriages, better friendships, and healthier work situations."
Many of the subjects of the Terman Project faced difficult challenges in their adult lives, including bitter combat in World War II, divorces, stressful jobs, and career reversals. Conscientious people had the ability to weather these problems. They displayed "self healing" personalities that helped them find their ways back to healthy lifestyle paths. People without such behavioral traits and healthy coping skills didn't fare as well and were often unable to bounce back.
Other strong longevity traits, Friedman and Martin say, include strong connections with other people and groups, either through marriage or outside activities. Also, "those with the most career success were the least likely to die young. In fact, on average the most successful men lived five years longer than the least successful." While happiness was not a cause of longer life, "the sense of being satisfied with one's life and achievement was very relevant to resilience."
[See 10 Trends in Longevity.]
Here are 10 questions used to create a personality scale that will help determine how conscientious you are. The scale is based on work done by Terman, the book's authors, and other research. The five possible answers to each question are the same:
1 — Very inaccurate.
2 — Moderately inaccurate.
3 — Neither accurate nor inaccurate.
4 — Moderately accurate.
5 — Very accurate.
1. I am always prepared.
2. I leave my belongings around.
3. I enjoy planning my work in detail.
4. I make a mess of things.
5. I get chores done right away.
6. I often forget to put things back in their proper place.
7. I like order.
8. I shirk my duties.
9. I follow a schedule.
10. I am persistent in the accomplishment of my work and ends.
Scoring for questions 1, 3, 5, 7, 9, and 10: Each answer is worth one to five points, matching the numbers of the answers (one point for very inaccurate, two points for moderately inaccurate, and so forth, up to five points for very accurate). For questions 2, 4, 6, and 8, reverse the scoring order (one point for very accurate, two points for moderately accurate, and so on, up to five points for very inaccurate).
Total scores can range from a low of 10 to a high of 50. "This score is a good measure of conscientiousness," the book says. "Total scores between 10 and 24 indicate very low conscientiousness . . . Scores between 37 and 50 suggest exceptionally high conscientiousness."
To test the accuracy of your own answers, ask your spouse or close friend to tell you what answers they think apply for you. They know you very well and might have a more objective view of your personality traits than you do.
Now, the good and bad news about how conscientious you are is that you can change your personality, but you can't invent a new one overnight. The highly conscientious people in the Terman study had little clue that such behavior would be associated with living a very long life. They behaved this way in their everyday lives because it came naturally.
"It doesn't matter how many New Year's resolutions you make," the book said. "In fact, rapid and pervasive changes are usually quickly abandoned by anyone undertaking them. Lasting adjustments happen with smaller, but progressive, steps."
Medical treatment is conspicuously absent from the book's longevity findings. "So-called modern medical cures have played a relatively minor role in increasing adult life span," the authors wrote. "Social relations should be the first place to look for improving health and longevity."
Corrected on 4/10/2011: A previous version of this article provided incorrect instructions for scoring the personality quiz.