In previous episodes of Healthcare Triage, we’ve discussed how people often misunderstand risk and how it affects them. We’ve also talked about how you can calculate the explicit metrics of numbers needed to treat, and numbers needed to harm. But people rarely use them. In spite of the existence of metrics to help patients appreciate benefits and harms, a new systematic review suggests that our expectations are not consistent with the facts. 

Most patients overestimate the benefits of medical treatments, and underestimate the harms; because of that, they use more care. That’s the topic of this week’s Healthcare Triage. 

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This study, published in JAMA Internal Medicine, looked at the accuracy of patients expectations of benefits and harms of treatment. They examined over 30 papers that assessed whether patients understood the upsides  and/or the downsides of certain treatments. Spoiler: They don't. In the 34 studies that assessed understanding of benefits patients overestimated their potential gain in 22 of them or 65%.

To the Research.

For instance a 2002 study published in the Journal of the National Cancer Institute asked women who had undergone a prophylactic bilateral (or double) mastectomy to estimate how much they thought the procedure had reduced their risk of breast cancer. On average, the thought they'd reduced their risk from 76% to 11%, an absolute risk reduction of 65%.   

However, the vast majority of the women in the study didn't have a BRCA genetic mutation - which would seriously increase their risk of breast cancer. Their risk before surgery was only 17%, so there's no way they could get even close to the 65% absolute reduction they predicted. Even the women with a BRCA mutation overestimated their risk reduction, but to a lesser extent. 

Another study published in 2012 in the Annals of Family Medicine asked patients to estimate the benefits of screening for bowel and breast cancer, and the use of medications to prevent hip fracture and cardiovascular disease. Two thirds of them overestimated the benefits of medications to prevent cardiovascular disease, and more than 80% of them overestimated the benefits of medications to prevent hip fracture. Further, 90% of patients overestimated the benefits of breast cancer screening and 94% overestimated the benefits of bowel cancer screening. What's more the researchers specifically asked the patients to tell them the minimum reduction in bad outcomes they would need to achieve to find the treatment worthwhile. And for three of the four studied interventions the minimum benefit demanded was higher than the actual benefit - so they shouldn't have gotten the test or therapy. 

Harms are misunderstood too. In the 15 studies for which harms were a focus, patients underestimated potential downsides in 10 of them or 67%. There's the study published in 2012 in the Journal of Medical Imaging and Radiation Oncology that asked patients to estimate the risks associated with a CT scan. A single CT scan exposes a patient to the same amount of radiation as 300 chest x-rays, and a potential increased risk of developing cancer from that exposure. More than 40% of patients underestimated a CT's radiation dose, and more than 60% of them underestimated the risk of cancer from getting a CAT scan.

Why do patients get it so wrong when thinking about risks and benefits? One reason could be the messages they hear. Doctors, direct to consumer ads and the media can bias our perceptions; they tend to focus on the benefits, but rarely quantify them. Healthcare centers, screening advocacy programs and drug ads all push us to talk to our doctors about getting treatment, but they don't talk about actual gains.

Doctors also aren't very good about communicating risks. A study in JAMA Internal Medicine in 2013,  found that less than 10% of patients were told about the over-diagnosis and over-treatment that cancer screening brings, even though 80% of patients wanted to know about such harms. This study and others indicate that patients might go for less care if they had more information about what they might gain or lose with treatment. Shared decision making, where there is an open patient-physician dialogue about benefits and harms might help with this. But the majority of patients still say that they'd prefer to leave medical decision-making to their doctors.

It could also be that some patients would us more of a certain type of care if they had more information. Many chronic conditions are still under-managed and under-treated in the United States; it's possible that people with theses conditions who had more information would use more care which would raise spending for those patients, but make them at least better off. There's also an argument to be made that people who overestimate the benefits of medicine to treat some conditions are more likely to take that medication regularly. Which might lead to better outcomes. In that case, the misinformation might be helping.

Regardless even though some patients might benefit somewhat from being ill informed, it seems wrong to argue that we should keep them in the dark. Many of the studies in the systematic review showed that people report that they'd opt for less care if they understood benefits and harms better. It's also possible that unrealistic expectations of care help patients cope with disease or provide them with some sense of control. Feeling hopeful about one's future is not to be dismissed, but those unrealistic expectations don't come cheap. We should at least consider the price that we pay for being uninformed.