Ineffective therapies can appear to produce convincing improvements in diseases.
ID: 134419 • Letter: I
Question
Ineffective therapies can appear to produce convincing improvements in diseases. Piantadosi (Sec 6.6.1, optional course text in syllabus) claims that there are at least 3 mechanisms by which this happens: (1) spontaneous improvements in the disease, (2) regression to the mean, and (3) the placebo effect. Consider the following scenario: Patients with severe emphysema are enrolled into a blinded, randomized trial testing Drug A vs Placebo. The outcome of interest is a measure of exercise capacity known as the "Six-Minute Walk Test (6MWT)," in which the distance a patient can walk in 6 minutes on a flat surface is measured (in meters) The 6MWT is administered at baseline and 6 months after the start of study treatment. Now suppose that the placebo group had 6-month outcomes that were surprisingly better than at baseline. Describe how each of the 3 mechanisms might be contributing to this improvement.Explanation / Answer
Therapy refers to the attempted remediation of a health problem. When symptoms improve after a therapy, patients as well as the healthcare providers tend to believe that therapy has worked or has improved the symptoms. Real, measurable improvement of the symptoms can sometimes occur even if the treatment is completely ineffective.
Human body has evolved immune systems and other mechanisms for repairing their own body. Hence, in such cases the symptoms of a disorder tend to decrease no matter how they are treated. This refers to spontaneous improvement of the disease. Thus, a disease can come and go naturally, making medical practitioners and patients assume that it is as a result of effective treatment.
When two independent sets of measurement is taken, people who had measures that were well above or below the mean during the first measurement, will display scores that are closer to the mean during second measurement. This statistical phenomenon where the data that was extremely higher or lower than the mean during the first time, coming closer to the mean during the second time is referred to as regression to the mean.
Placebo effect refers to a patient’s belief in a treatment. It can be attributed to several factors including the medical practitioner’s appearance, confidence, gentle touch, or even the attitude of the nurse. Even an inactive treatment with placebos (substances with no medical effects like water, saline solution or sugar pills) can thus influence the efficacy of the result.
Emphysema is a progressive lung disease that leads to shortness of breath due to inflammation of alveoli.
According to the question, the placebo group showed improvement after 6 month treatment. This convincing measurable improvement might have occurred due to
(1) Spontaneous improvements in the disease.
A person with a strong immune system can respond to challenges positively causing the improvement of the disease.
(2) Regression to the mean
Severity of a disease is measured imperfectly and with random variation. If treatment of a disease is done at the time of peak severity, the outcomes will be seen to be less severe, that is the measurements will be dispersed around the mean, even if there is no change in the underlying condition. Thus, the measures will be closer to the average, purely due to statistical reasons.
(3) Placebo effect
Placebo might have played the role in improving the patient’s condition. This is due to the fact that the patient had the expectation that the treatment will be helpful.