According to U.S. Census numbers, in December 2010, 71,991 Americans were at least 100 years-old, a rise of just over 37,000 people from 1990. Centenarians are America's fastest growing age cohort. In a previous post, I shared a census centenarian estimate of roughly 600,000 for 2050. Their highest-end estimate is 4.2 million. We're living longer largely due to a combination of genes, much less childhood mortality and health care advances.

So what will get us to 100? A friend of mine just turned 99, and I'm quite confident she'll reach 100, as she'd like to nail the century mark. I've known her all my life. A small business owner into her 80s, she lives in her own apartment, has always followed current events and is cognitively sharp, humorously irreverent, and tough. Yet, she's never exercised, consumed Ritz crackers not wheat germ, and she's long been quite content having herself as company rather than a non-stop social calendar. I've always thought she hit the gene lottery big time. But genes are generally thought by researchers to account for about one-third of longevity, the rest being lifestyle and good old luck.

The New England Centenarian Studyat Boston University's School of Medicine provides insights beyond the gene factor, illustrating that getting to the century mark is not only still a major accomplishment, but provides frosting on life's cake, with a healthier life.

- Good Health: If you make it to 100, you're typically in pretty darn good health. Centenarians on average escape physical disability until age 93, which is remarkable. Fifteen percent in the Boston U study had no physical disability.

- Lean and Smoke-Free: Few centenarians are obese and have no significant history of smoking.

- Healthy Minds: About 15% had no change in their cognitive ability and Alzheimer's and dementia were not inevitable.

- Optimism and Worry: Centenarians generally handle stress well, not dwelling on things, and having an optimistic outlook. But a new look on 80+ years of longevity research says for some people stress and worry can actually be good for their longevity march.

Want Longevity? – It's About Being Conscientious

In 1921, psychologist Lewis Terman began studying 1500 children in a longitudinal study that lasted more than 80 years. In their new book "The Longevity Project," researchers Leslie Martin and Howard Friedman write about their two-decade analysis of Terman and his successors' study.

A big takeaway: People who are highly conscientious live longer.

Conscientious people, for example, take better care of themselves, avoiding risks such as drugs and smoking. Conscientious people are more selective about their endeavors and relationships – choosing healthy, invigorating ones. For example, their work may be stressful, but they like it. They also say more conscientious people typically find life partners and friends who enrich them.

Try the Living to 100 Life Expectancy Calculator

Unfortunately we haven't yet eradicated cancer and other life-shortening disease, but the new old age is longer for many. And we know more about why that is and will learn more. In the meantime, try this calculator from Dr. Perls, director of The New England Centenarian Study.

I also invite you to read these 50 Tips for Aging Gracefully, many of which come from Ecumen customers, the average age of which is 83, on their thoughts for longevity. And please add your own.