The average person living in an industrialized nation has the genetic makeup to hang on until 87, barring unforeseen circumstances. But whether you reach that point (or live even longer) depends on six core criteria -- attitude, genes, exercise, interests, nutrition and smoking, according to Thomas Perls, director of the New England Centenarian Study at Boston University. (Take the first letter of each factor, revising the last to read "Get rid of smoking," its intent, and guess what it spells: AGEING.)

For an estimate of how long you'll be around, together with a detailed explanation of the role each factor plays in longevity, check out Perls's online calculator at www.livingto100.com.

Want a simpler test? Try this.

Assume you'll live to be 87. Then add or subtract years based on the following:

Attitude Are you optimistic? Do you generally approach life in good humor? Are you able to let go of things that are stressful (as opposed to dwelling on them)? If no, subtract five years.

Genes Do you have some family members who have lived into their nineties or later? If yes, add 10 years, since exceptional longevity runs strongly in families.

Exercise Do you set aside at least 30 minutes three days a week to exercise? Be honest. If no, subtract five years.

Interests Do you do things that are cognitively challenging on a regular basis? Yes gets you five years.

Nutrition Do you have a diet that facilitates saying lean? Subtract five years if you don't.

(Get rid of) Smoking If you smoke, subtract 10 years. You knew that.

-- Rita Zeidner