Healthy Life Calculator Frequently Asked Questions (FAQ)

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• What do these predictions mean?
• How might I use these predictions?
• Is this calculator different from other things I’ve seen on the internet?
• Please provide more details.
• How were the predictor variables chosen? And why wasn’t my favorite variable one of them?
• What are some reasons that the CHS predictions may not be accurate?
• If I'm Healthy and Able, does that mean I won't have dementia?
• How accurate are these predictions for me?
• I am disappointed in my predictions. How can I improve them?
• Where can I learn more about this calculator?

What do these predictions mean?

The predictions are the average values for people whose information was similar to yours, calculated from a large dataset that was collected for a research study paid for by the National Institutes of Health.

• Years of life (YOL) is the average number of remaining years that people like you lived.
• Years of Healthy Life (YHL) is the average number of remaining years that people like you were in excellent, very good, or good health (Healthy).
• Years of Able Life (YABL) is the average number of remaining years that people like you were able to perform all of their activities of daily living (walking, getting out of bed, feeding dressing and bathing themselves, using the toilet) without difficulty (Able).
• Years of Healthy and Able life (YHABL) is the average number of remaining years that people like you were both Healthy and Able.

How might I use these predictions?

You may be considering major changes in your life, or even deciding not to make such changes right now. If you can expect many more years of healthy and able life, you probably don't need to limit your choices because of your health. You may also want to plan for the years in which you will not be healthy and able.

As an example, consider "Mary", who is 70 years old and would like to put off making any major changes until she is about 80 (10 years from now). Mary is quite healthy, and gave the best possible answers to all of the CHSHLC questions. Based on the calculator, the average person like Mary was both Healthy and Able for another 14 years, which would take Mary well beyond 80. But Mary might not be average. The calculator also says that about 26% of people like Mary had fewer than 10 Healthy and Able years. If she thinks that 26% is too risky, Mary might choose to make her plans sooner.

Is this calculator different from other things I’ve seen on the internet?

The United States lifetable is well documented, accurate and easy to find on the internet (for example, at http://www.ssa.gov/oact/STATS/table4c6.htm ). But the YOL predictions from the lifetable are shown only by age and sex, and do not take any account of your health or behaviors. Other web sites provide predictions of life expectancy, but to our knowledge none of them explains how the predictions were created or how accurate they might be. There are no national predictions of YHL, YABL, or YHABL. The Healthy Life Calculator addresses these needs.

Please provide more details.

These predictions are based on data from the federally-funded Cardiovascular Health Study (CHS). (see https://chs-nhlbi.org/ ). That study enrolled about 6000 older adults in 1990 and followed them through 2013 and still continues. In 1990, ages ranged from 65 to 99 and the average age was 73. The study recorded hundreds of health characteristics about each person at that time. In every year after that we found out, for each person:

• Was the person still alive?
• Was the person’s health excellent, very good, good, fair or poor? (health status)
• Did the person have difficulty with any of the activities of daily living? (ADLs)

It is helpful to think of the predictions as the average values (from the CHS dataset) for people who were like you in 1990. That is, we found people with similar responses to yours, and reported the average YOL, YHL, YAL and YHABL for those people. (The predictions were actually calculated using a statistical technique called multiple regression which helps to make better predictions).

More technical detail is given in a scientific journal article. See http://journals.sagepub.com/doi/full/10.1177/2333721415605989

How were the predictor variables chosen? And why wasn’t my favorite variable one of them?

We decided in advance to use the users' age and sex, as well as their health status and ADL status in 1990 as predictors. Then, we screened the hundreds of other health variables to find additional good predictors of YOL, YHL, YABL, and YHABL. We eliminated items that a person might not be able to answer, such as laboratory results. From the remaining variables we chose the best predictors, trying to keep the number of variables small so the questionnaire would be short enough to answer easily. A variable that was not selected, such as obesity or cancer, might not have been a very good predictor for people once their other characteristics were accounted for. (People under active treatment for cancer in 1990 were not eligible to join CHS, which explains why it was not a good predictor). In some cases, the variable might not have been measured at all in 1990, such as information about how long your parents lived.

If I'm Healthy and Able, does that mean I won't have dementia?

It is, unfortunately, possible to be both healthy and able but to have dementia. Fortunately, about 75% of older adults have more years without dementia than they have years of healthy and able life. So most people are likely to be dementia-free while they are Healthy and Able.

How accurate are these predictions for me?

The predictions should be useful for planning, but of course not everyone will have the average result. In addition to providing predictions, the calculator also estimates the chances that a person will do more than 5 years better, or 5 years worse, than the average. In the example above, Mary used this information in making her decision.

What are some reasons that the CHS predictions may not be accurate?

There are three main concerns. First, the people in the CHS study were not perfectly representative of all older adults in 1990. People who were being treated for cancer or who used wheelchairs at home were ineligible, and people who volunteer for studies like this are usually healthier than average. Predictions based on their experience could be too optimistic. Predictions for older adults who are very old or sick may be less accurate.

A second concern is that there have been many improvements in health care since 1990. For that reason, a person who is 75 now may have better prospects than a person who was 75 in 1990. But other changes such as increases in antibiotic resistant bacteria or environmental pollution could work the other way. The encouraging news is that our average YOL predictions were very close to the numbers in the current United States lifetable. So some of these potential problems may not have existed, or their effects may have averaged out.

Finally, some important features of your own health may not have been taken into account. That is, you may not be average. Your parents may have lived well into their 90s, or you may have a serious disease that was not asked about. You may want to adjust these predictions up or down to reflect your personal situation. It is also possible that your specific features were already accounted for by the health and medication information that you did provide, and adjustment would not be needed.

I am disappointed in my predictions. How can I improve them?

The variables in this study were chosen to provide the best predictions, not necessarily to give you advice. You could improve your score by changing your answers, but that wouldn’t necessarily improve your health (for example, decreasing your number of medications might make your health worse!). You probably already know about things you might do to improve your health, and may wish to discuss these with your doctor.

Where can I learn more?

More technical detail is given in a scientific journal article:

Diehr, P., Diehr, M., Arnold, A., Yee, L. M., Odden, M. C., Hirsch, C. H., Thielke, S., Psaty, B. M., Johnson, W. C., Kizer, J. R., and Newman, A. (2015). Predicting Future Years of Life, Health, and Functional Ability: A Healthy Life Calculator for Older Adults. Gerontology and Geriatric Medicine, 1, 1-10. https://doi.org/10.1177/2333721415605989

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See also http://journals.sagepub.com/doi/full/10.1177/2333721415605989

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