Updated: December 03, 2018

By Anne Harding

MONDAY, Oct. 27 ( — People who take statins and end up in the hospital with pneumonia are more likely to survive than those who are not taking a cholesterol-lowering drug, according to a study in Archives of Internal Medicine.

It's possible that statins, some of the most commonly prescribed medications in the world, may help fight lung infections. On the other hand, people who take them may be in better health to begin with, which could explain their ability to survive a serious infection.

If statins are shown to fight infection, they could prove to be "a cheap and effective way of treating pneumonia, which would be wonderful," says Reimar W. Thomsen, MD, PhD, of Aarhus University and Aalborg Hospital in Aalborg, Denmark, who led the study. "We really need new treatment options for pneumonia because it's a great burden on health-care systems."

Animal research has shown that statins reduce inflammation and fight blood clotting, so it's scientifically plausible that they could help treat infections too. There have been studies showing benefits of statins in patients with sepsis, a life-threatening blood infection, as well as pneumonia.

However, the study could also be picking up on a so-called healthy-user effect. Healthy users tend to see their doctors regularly, take their medications as prescribed, exercise, eat their fruits and veggies, and avoid smoking.

Such people also tend to be prescribed medications like statins—or, if they were menopausal women a few years ago, estrogen. In that case, the healthy-user effect made it look like these women were getting benefits like stronger bones and healthier hearts from the hormone—until the Women's Health Initiative study demonstrated that estrogen was actually harmful.

In the new study, Dr. Thomsen and his team looked at 29,900 people who had been hospitalized for pneumonia between 1997 and 2004. Overall, 1,371, or 4.6%, of the people were taking statins. Denmark has universal health care, so they were able to gather information on virtually every hospitalization in the region they were studying, as well as every prescription filled.

Thirty days after being hospitalized, 10.3% of the statin users had died, compared to 15.7% of the nonusers; 90-day mortality rates were 16.8% for statin users and 22.4% for nonusers. Dr. Thomsen and his colleagues used several statistical techniques to account for the healthy-user effect—for example, adjusting for other illnesses such as diabetes or kidney disease, age, socioeconomic status, and other medications patients took. The reduced risk for mortality with statins remained, and it was particularly strong for people over 80.

"This particular study is very rigorously done; also, it's quite elegant," says Sumit R. Majumdar, MD, an internist and associate professor of medicine at the University of Alberta in Edmonton, Canada, who has also studied statins and pneumonia, but wasn't involved in the current research. "It's as good a study as you can do using observational data."

In their own research, Dr. Majumdar and his colleagues found that the relationship between lower mortality and statins disappeared after they accounted for whether patients had gotten recommended flu and pneumonia shots, lived in a nursing home or on their own, could walk without assistance, and other factors.

In Dr. Thomsen's study, Dr. Majumdar points out, statins cut mortality risk by 5%; however, the best available drug for treating severe infections in intensive care patients, known as activated protein C, only cuts mortality by about one-third as much.

"I always worry a bit when things are too good to be true, because it usually means they're too good to be true," Dr. Majumdar says. He is also skeptical because clinical trials comparing statins to placebo, which included 40,000 to 50,000 patients, did not find an infection-fighting benefit. And, he notes, similar research has linked statins to a lower risk of dementia, hip fractures, and diabetes as well as infection-related diseases, which further supports that the healthy-user effect is at work.

Dr. Majumdar and Dr. Thomsen agree that the only way to answer the question of whether statins fight infection will be to conduct a clinical trial, in which patients with an infection are randomly assigned to take a statin or a placebo.

According to Dr. Majumdar, two or three such studies are now underway to investigate statins for treating infection, which means there will be a definitive answer soon. Then it will be clear if it's the statins—or the healthy person taking them—that fight infection.