Health Statistics

Health statistics are important. They are needed to make informed decisions not only about health care for you and your loved ones, but also for he health care of the nation. Unfortunately, there are a number of problems regarding health statistics. There are all sorts of health statistics coming from all sources. One problem is that the different sources have different agendas. This potential bias should be obvious for drug companies, but there is also potential bias coming from health agencies, which one would presume to be neutral. Agencies can believe in certain policies and then present statistics to support these policies.

There is a very good book to help you understand health statistics. It is Know Your Chances: Understanding Health Statistics by Steve Woloshin, MD, MS, Lisa M. Schwarts, MD, MS, and H. Gilbert Welch, MD, MPH. They help you see the hype in medical news, ads, and public service announcements. The publisher is the University of California Press,

They state that if there were a hall of fame for exaggeration, survival statistics would get a lifetime achievement award. These statistics are frequently used in cancer screening. Survival statistics can be reported for any span of years. The choice is arbitrary, but the five year survival rate is quite common. The five year survival rate is the ratio of the number of patients alive five years after diagnosis divided by the number of patients originally diagnosed with the cancer. This statistic has its uses. For example, if different treatments for cancer patients were being evaluated, this would be a good statistic to use to compare the relative effectiveness, or lack thereof, for the respective treatments.

However, it is not a good statistic to use as evidence to support cancer screening. Cancer screening is the policy of testing everyone of a specific demographic or age group. The correct statistic for evaluating the effectiveness of screening is the Annual Death Rate. The Annual Death Rate is the ratio of the number of people who die from the disease over a year divided by the number of people in the demographic age group of interest. If screening is effective, then it should be reflected in decreasing death rates.

A reasonable question is how could there be survival statistics indicating that screening is effective, but annual death rates indicating that screening is not effective. Few people seem to realize that there are costs to early testing. Early cancers or precursors of cancer can go away on their own. Some cancers are so slow in developing that you are likely to die from something else before you would die from the cancer.

For example, the 5-year Survival Rate for the deadly skin cancer melanoma improved from 49% in 1950 to 92% in the most recent data available. Death rates have gone up during this period from 1 death in 1,000 to almost 3 deaths in 1,000.

One of the bests examples here can be found in screening for prostate cancer. For decades the Prostate Specific Antigen Test (PSPA) was regarded as mandatory for all men in a certain age group. Only recently, was this position changed. Now the PSPA test is not generally recommended, even for high risk groups. It is to be given only after consultation with a physician. The reason for this change was the discovery that the test was not affecting the Annual Death Rates. Cancers were being caught and treated, which resulted in improved survival rates, but there was no corresponding decrease in the Annual Death Rates. Prostate cancer advances at a wide range of rates. Although some prostate cancers advance relatively quickly, others advance so slowly that a man if much more likely to die from something else before the prostate cancer can kill him.

One way of looking at the difference between the survival rate and the annual death rate is to regard it as an index of unnecessary treatments. Thousands of men had their prostate glands removed with some of them suffering the side effects of impotence and incontinence. These same men could have lived on without surgery and eventually died of something else.

© Douglas Griffith and, 2010. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

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