Thursday, August 5, 2010

Health Care Stats from Time

Time Magazine, my regular bathroom reading material, continues to report statistics from academic journals with insufficient context or explanation. Here are three recent clips.

* 165% - Increase in risk of STDs -- including HIV -- in men who take erectile-dysfunction drugs.

Obviously, men with ED taking ED drugs are going to have more sex overall than if they did not take the drugs, and having more sex means more risk of STDs (unless this sample is comprised entirely of men who only ever have sex with disease-free partners or partners who already share the participants' STDs). But that isn't necessarily what this clip says. This clip could also mean that ED drugs increase the risk of contracting STDs assuming that sex is held constant. The amount of sex study participants had is a confound in this study, and researchers usually try to control for confounds using statistical techniques so that we can better see what direct effects a determinant (drugs) has on an outcome (STDs). Maybe the ED drugs affect membrane permeability, body fluid viscosity, pore dilation, or immune system function. If the drugs affect any or all of those physiological factors, they could increase STD risk even if the men did not have more (or different) sex while taking the drugs. This clip is unclear, and therefore not useful by itself in informing decisions regarding ED drug use or endorsement.

* 767,000 - Number of lives saved through improvements in cancer care over the past 20 years.

"Lives saved" is a terrible term. Everyone dies. If you stop someone from dying from cause A today, you have extended that person's life until he dies from cause B later. A much more useful thing to do is measure life-years saved, which of course requires estimations based on a large sample of data, but is frequently done. Usually even better than that is measuring risk-adjusted life-years saved, when possible, quality life-years (arguably subjective, but useful and there is good consensus), or both together. I am appalled by how much money is spent on certain cancer treatments that extend a person's life by a few months of immobility, pain, and/or mindlessness. That money could do vastly more good for people spent elsewhere. If cancer treatment lets a person live long enough to die from a heart attack, kidney failure, infection, pneumonia, or whatever, it has still "saved that person's life." Baloney.

I want to see a list of each treatment's cost per quality-adjusted life-year extended. All treatments. Our health care system has finite resources. Organize the list in increasing order by that cost. Then have our system provide treatments to people in that order until it is out of resources. This is not a crazy idea. This maximizes the benefit that people get from our system. Real people with families, friends, jobs, and lives. When you or someone you care about gets a condition with an inefficiently high cost, how many other people are you willing to deny more-effective care so that you or your person can have care? Are you more important than other people? Who would you kill so you can have a few more months?

Is 767,000 good or bad? How many people had life-threatening cancer? How many people died from other things, and what would it have cost to save them? What would have happened if we spent that money on nutrition programs, or clean water for Africa? Just examples.

* 13.2 million - Estimated number of people who will die from cancer each year by 2030, double the number who died from it in 2008.

A couple obvious things pop up. One, there will be more people in 20 years. Quantities are not useful to us by themselves. We want to know proportions. Two, what will the people dying from cancer not be dying of in 20 years? Are we expecting more people to die from cancer because people won't die so much from heart disease or accidents or infections? Everyone dies. Causes of death are a zero sum game. As we die less often from heart attacks, we're just living long enough for the cancer to get us. Heck, if we cured all kinds of cancer today, would you be surprised the next day when the forecast was for triple the rate of deaths by heart disease? No.