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As I get older, I find myself drawn to news reports and research findings that provide information about how long I might live. After all, this is a key piece of information that would help me plan the most strategic and successful , even though I think that I do not really wish to know for sure how long I have left. Much aimed at people in my age group involves dietary choices, vitamin and mineral supplements, and medications that directly or indirectly promise not only more years of life, but more years of healthy, productive life. Many, if not most, of these promises are based upon little more than wishful thinking and anecdotal evidence. Hence, it is always exciting for a researcher like myself to see studies that bring actual scientific data to bear.

In a recent issue of Psychological Science, a team of European scientists including Stephen Aichele of the University of Geneva, Patrick Rabbit of Oxford, and Paolo Ghisletta of Distance Learning University in Switzerland published such a study. The researchers reported the results of a longitudinal study of more than 6,000 British individuals conducted from 1983 to 2012. The average age of the participants was 64.7 years when they first joined the study, but ages ranged from 41 to 93.

Key medical and data including blood pressure, cholesterol levels, diabetes, and tobacco and use, were collected at three- to six-year intervals throughout the 29-year duration of the study. Daily life measures such as the number of prescription medications taken, sleep patterns, hobbies, and the rated difficulty of activities such as climbing stairs, traveling, preparing meals, and managing social interactions were also examined.

In addition to those measures, each participant had his or her cognitive abilities assessed up to a total of four times at four-year intervals. These included measures of:

Crystallized (the ability to use knowledge you already have);

Fluid intelligence (the ability to solve new problems, use logic, and identify patterns);

Verbal ;

Visual memory; and

Mental processing speed (how long it takes to perform a mental task).

All together, the researchers looked at 65 different mortality risk factors as they tracked participants through the later years of their lives. Once the number crunching was finished, the factor that rose to the top was surprisingly simple and straightforward.

The most sensitive measure of longevity was the individual’s own subjective evaluation of how healthy he or she felt. In other words, a person reporting that he or she feels healthy outweighed any other single predictor of a long life, including any medical measures such as cholesterol levels and blood pressure.

Other variables that fell into the top group of predictors included being female; not (or at least not smoking for very long); and cognitive processing speed.

The researchers seemed genuinely surprised that psychological variables such as subjective health and mental processing speed were better predictors of mortality risk than all the other predictors they studied. It has long been known that remaining cognitively active is associated with aging well, but it has never been clear if the cognitive activity is the cause of healthy old age or the result of remaining healthy into one's golden years. The findings of this study confirm the association between the two domains, but cannot resolve how the cause-and-effect relationship plays out.

In a completely unrelated study published in 2003, researchers asked college students to rate the and perceived health of individuals in photographs from the 1920s taken from high school yearbooks. The researchers then tracked down the age of death for the people whose pictures were rated. They discovered that having a handsome or beautiful face as a teenager predicted a long life but, ironically, participants' judgments about the perceived health of the photographed individuals were completely unrelated to how long they lived. I replicated this finding several times in projects in my Evolution and Human Behavior class by having students do the same thing with photographs taken from Knox College yearbooks from the 1920s.

The explanation for a pretty face predicting a longer life appears to be that attractive faces are symmetrical and "normal"—average in terms of things like size of nose, distance between the eyes, etc. These qualities may reflect a lack of unusual , good health, and freedom from parasites or physical —all of which are good if you wish to live long and prosper.