Patients often come to me seeking advice about what they can do to live longer. The number of things that have been proven to extend life, however, remains shockingly small. What follows are things that have enough support in the scientific literature that I generally recommend them (though the strength of the evidence varies even with these):

1. Take simvastatin (brand name Zocor). That is, if you have coronary artery disease. (This is one of those drugs that doctors joke should be put in our water supply.) A landmark trial called the 4S Study (click on the “Look Inside” button to read the article) showed that people with heart disease who take simvastatin will reduce their risk of dying from any cause by 30% (relative risk).
2. Take ACE inhibitors if you have heart failure. Though we’ve known for decades ACE inhibitors make such patients live longer, studies also show a shocking number of such patients aren’t taking them. (This is the other drug that doctors joke should be put in our water supply.)
3. Wear oxygen if your PaO2 (partial pressure of oxygen in your blood) is below 55 mmHg, as in severe emphysema. Lots of people want to wear oxygen for lots of reasons, but the only good reason to do so is if you PaO2 is below 55. And then you should do it not so much because it will make you feel better (it may do so, interestingly, by improving your energy, but strangely not by making you feel less short of breath), but because it will prolong your life.
4. Get annual Pap smears (and mammograms). The interval for screening Pap smears isn’t the same for all women, but it too increases the likelihood of living longer. So does mammography (though the age at which to begin screening mammograms remains controversial).
5. Get screening colonoscopies. Like Pap smears, how often you should get one varies depending on your baseline risk, but it too has been shown to decrease the likelihood of death. Screening exercise treadmill tests, on the other hand, the most frequently requested screening test, has been shown in otherwise low-risk individuals not to increase lifespan and should be avoided: the risk of false positives (that is, the test says you have coronary disease when you don’t) in low-risk individuals is higher than the likelihood of true positives (this turns out to be especially true for women) and only exposes patients to unnecessary invasive testing like cardiac catheterizations, which have very real risks.
6. Exercise. Most of us already know that exercise makes us healthier. Some may also believe it makes us live longer. Those who do are probably right, though it depends on who’s doing the exercising. Statistically speaking, middle-aged men who exercise will live longer than middle-aged men who don’t. Statistically speaking, elderly women will also live longer than elderly women who don’t. Middle-aged women probably will live longer than middle-aged women who don’t. Elderly men, interestingly, won’t live longer than elderly men who don’t.
7. Assume responsibility. In both elderly men and women, however, simply being made to feel a sense of responsibility has been found not only to improve daily functioning but also to increase lifespan. In a study of nursing home patients by researchers Ellen Langer and Judith Rodin, residents on one floor were given a plant for which they themselves were expected to care (the experimental group) while residents on another floor were given a plant for which their nurses would care (the control group). After three weeks, 93 percent of residents in the experimental group showed an overall improvement in socialization, alertness, and general function; in contrast, for 71 percent of residents in the control group functioning actually declined. And in a follow-up study eighteen months later, half as many of the residents who’d received plants for which they were expected to care by themselves had died as the residents who’d been given plants for which their nurses cared.
8. Learn to be optimistic. A former resident of mine, Hilary Tindle, just recently published a book, Up: How Positive Outlook Can Transform Our Health and Aging, summarizing the research on optimism and aging, which shows that optimists live longer than pessimists. For a discussion about how to become more optimistic, see my own book, The Undefeated Mind, chapter 4.
9. Train yourself to view aging as a positive. Studies show that people who have positive self-perceptions of aging have a strong will to live and that having a strong will to live actually seems to increase longevity.
10. Be happy.  So much easier said than done, of course. Happiness, however, doesn’t seem just correlated with longevity. It actually seems to cause it.

Alex Lickerman is an internal medicine physician at the University of Chicago who blogs at Happiness in this World.  He is the author of The Undefeated Mind: On the Science of Constructing an Indestructible Self.