Archive for February, 2010

Interpreting Medical Statistics: Risk Reduction

February 27, 2010

In 1995 the results of the West of Scotland Coronary prevention study were presented in the following press release: “People with high cholesterol can rapidly reduce…their risk of death by 22% by taking a widely prescribed drug called pravastatin sodium. This is the conclusion of a landmark study presented today at the annual meeting of the American Heart Association.” 1 One cannot interpret this statistic correctly without knowing what is divided by what. The percentage presented was one of relative risk reduction. It was based on the number of deaths per 1,000 people with high cholesterol. Thirty-two of these people taking pravastatin died. In the placebo, or control or comparison, condition 41 died. The computation was for relative risk reduction, so the difference between the pravastatin and placebo groups, 9, was divided by the number of people who died in the placebo group, 41, to get the 22% figure. Usually when you hear a percentage reported, particularly in the news or in advertising, it is for relative change (for example, the inflation rate has increased by 50%, which could mean that it had gone from 1% to 1.5%) because that is more impressive.

There are other means of reporting this result that might not be as impressive, but might be more revealing of the truth. Absolute risk reduction is the proportion of patients who die without treatment (the placebo group) minus those who die with treatment. In this case, pravastatin reduced the number of people who died from 41 to 32. So the absolute risk reduction is nine in 1,000, which is 0.9%.

Perhaps an even less impressive means of presenting these results would have been is the number needed to treat (NNT). This is the number needed to treat to save one life. Here the NNT to save one life in a thousand is 111 (1,000 divided by 9 (41 in the placebo group minus 32 in the pravastin group).

So when you hear a percentage, be sure you know how it is computed. It might also be useful to compute other types of statistics, absolute risk reduction, NNT, to get a more accurate feel of the result.

1This example is taken from Gerd Gigerenzer’s book, Calculated Risks: How to Know When Numbers Deceive You. 2002. New York: Simon & Schuster. I highly recommend this book.

The Healthy Memory Blog

February 11, 2010

Welcome to the Healthymemory Blog. As the name implies, one objective of this blog is to provide information to aid in keeping memory healthy. But we aspire to go beyond keeping memory healthy and pursue means of enhancing and growing memory. To this end, this blog pursues three themes: Human Memory: Theory and Data, Mnemonic Techniques, and Transactive Memory. You can locate the blog posts under each theme by clicking on their titles under Categories on the sidebar.

Human Memory: Theory and Data provides information on how memory works. Having a basic understanding of how memory works is important to maintaining a healthy memory. You might discover that the memory difficulties you are having are normal. Aging Baby Boomers might discover that memory lapses they attribute to aging are not due to aging at all. Here you will also find information on logical errors and biases as well as on health statistics and how to interpret them. You will see that logical errors and biases are the result of a certain type of processing. There are also limits to short term memory that can contribute to erroneous and biased processing. Other errors are due simply to not having the appropriate information in memory or having erroneous information in memory.

Mnemonic techniques are techniques for improving memory. Obviously they address the problem of memory failures directly, but they also have a secondary benefit. The secondary benefit is that they provide good exercises for memory. The call upon using your imagination and recoding information into a more memorable form. You can find a memory course in this category.

Transactive memory is a little known topic. It refers to memories stored outside your individual biological memory. There are two types of transactive memory: human and technical. You do not need to hold all information in your head. You can also get by with a little help from your loved ones and friends. Technical transactive memory includes all the information stored in all types of technology from note pads to books, to the internet. Technical aids can benefit memory recall, but the vast resources on the internet provide a splendid opportunity to cognitive and personal growth.

There is much to read on the Healthymemory Blog. Read what you need and what interests you. Please feel free to ask questions and make comments by clicking “leave a comment.”

© Douglas Griffith and healthymemory.wordpress.com, 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 healthymemory.wordpress.com with appropriate and specific direction to the original content.

The Benefits of Testing

February 9, 2010

The distinguished psychologist Roddy Roediger was invited to give the keynote address for the 50th Anniversary meeting of the Psychonomic Society. The title of the address is “The Critical Role of Retrieval in Enhancing Long-Term Memory: From the Laboratory to the Classroom.” A streaming video of this keynote address came be found at

psychonomic.org/annual_meeting.html

Roediger begins his address by stating the implicit bargain that is usually made between teachers and students. Students don’t like taking tests and teachers don’t like giving them. Not only does the teacher need to construct the test, but she also needs to grade them, a time consuming task. So testing and exams are usually kept to a minimum. Moreover, testing is used to measure learning and the assumption has been that little or no learning takes place during testing. Roediger’s address should disabuse anyone of this notion.

Roediger presents a series of studies that vary the respective number of study and test trials. Little difference was observed during learning. But on retention tests that were given two days later, retention was solely a function of the number of test trials. He presents a series of studies varying the materials and the nature of the tests, but they all basically hammer home the same theme. Not only does learning occur during testing, but more learning occurs during testing than during study. One study done with a group of middle schoolers showed that repeated testing had the result of raising the average grade from a C+ to an A-.

It is interesting to examine the subjective ratings of students and test participants. They feel that they are learning more during study than during testing. When students keep re-reading highlighted material in a textbook, they get the filling that they really know the material and their confidence goes up. However, when a student tries to recall material from memory and fails, confidence is lowered. Yet the looking up of the material that was forgotten is more beneficial and the student has a more realistic appraisal of what is known and what needs to be studied. In the end, this latter experience is more beneficial.

The actual attempt to remember information forces the person to access the correct retrieval routes to that information. If the information is found, then that retrieval route is strengthened. When it is not found, the information is restudied and the retrieval route relaid. More effort is involved in testing than simply studying material, and there is evidence that this increased effort is also beneficial.

So what are the lessons to be learned here? First of all, cramming is not recommended. Even if you learn enough to pass the test, the information will quickly be lost. So its availability on a final exam or later in life is questionable.

Secondly, test yourself and recited the material frequently. This testing should be even more effective if spread out over time.

And what, if any, are the implications for the education system? Break the silent bargain between teachers and students and test more frequently. Roediger and his colleagues have taken to the practice of having a ten minute test at the end of every lecture. This practice not only forces students to keep up, but it also leads to better lifelong learning.

© Douglas Griffith and healthymemory.wordpress.com, 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 healthymemory.wordpress.com with appropriate and specific direction to the original content.

When to Rely On Transactive Memory

February 8, 2010

Say you encounter a new piece of information. This piece of information could be as simple as a phone number or a major work that is central to your interests. Should you commit this information to your personal memory, or should rely upon external, transactive memory? This question has arisen in educational circles with respect to the multiplication tables. Now that calculators are ubiquitous, is there still a need to memorize the multiplication tables? The need for this can be argued from two points of view. One has to do with the standard for knowing. If something is important for understanding arithmetic and advanced mathematics, should not this information be resident in memory? If the answer is “yes”, then this needs to be committed to memory.

The second point of view is one of convenience. Will one always have a calculator available? Will it be worth the time and effort in finding a calculator to perform multiplication? What about potential emergencies when it might be a matter of life or death, but no calculator was available? If convenience is a factor, that alone might be justification for committing the multiplication tables to memory.

We are confronted with this problem everyday. Suppose you encounter a phone number. Do you need to commit this number to memory? There are mnemonic techniques that facilitate the memory for these numbers (see the blog posts “Remembering Numbers,” “More on Remembering Numbers,”, “Three Digit Numbers,” and “Remembering Even Larger Numbers.”). But these techniques require mental effort. Should you extend this mental effort? Not surprisingly the answer is, “It depends.”

Wayne Gray and his colleagues have developed a hypothesis, the soft constraints hypothesis, to address this question.1 This hypothesis says that your choice will be based upon a rational cost benefit analysis. In other words, if this phone number is to be used only once, you will most likely not commit it to personal memory, but will rely upon transactive memory, a piece of paper for example. However, if you are going to use this number frequently and cannot rely upon speed dial (a type of transactive memory), you will commit it to memory. They present extensive and thorough evidence supporting the notion that this is, in general, how people behave. However, people do not always behave in this rational manner. In my personal experience there are times when I have relied way too much on external supports when it would have been more efficient to commit the information to my personal memory.

At other times, however, the criterion will concern how deeply you need to understand the information. Do you only need to bookmark or tag where to find it should you need it in the future? Although you need the information, it is still not central to your primary interest and can get by with knowing where to locate the information. Or is the information central to your understanding and needs to be committed to your personal memory. You would not usually commit a major piece of work central to your interests to verbatim memory, but you would commit its essence and its major points to personal memory. The number and depth of those points would depend upon the importance of the particular work.

1Gray, W. D., Sims, C. R., Fu, W-T, Schoelles, M. J. (2006). The Soft Constraints Hypothesis: A Rational Analysis
Approach to Resource Allocation for Interactive Behavior. Psychological Review, 113, 461-482.

© Douglas Griffith and healthymemory.wordpress.com, 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 healthymemory.wordpress.com with appropriate and specific direction to the original content.

Where to Find Good Health Statistics

February 7, 2010

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. Different statistics are appropriate for different purposes. The immediately preceding blog post, Health Statistics, discussed the difference between survival rates and death rates.

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, www.ucpress.edu.

The following websites are recommended sources for good, reliable health statistics. All these sites are free. The first set of sites were created primarily for consumers.

The Center for Medical Consumers is an independent, nonprofit organization. It provides recent health news and a skeptical view on health claims.

medical consumers.org

Consumers Reports Best Buy Drugs is another independent, nonprofit organization. It uses the Drug Effectiveness Review Project to compare the benefits, side effects, and costs of different drugs for the same medical problem.

consumerreports.org/health/best-buy-drugs/index.htm

The Ottawa Health Research Institute for Patient Decision Aids is an academic affiliate of the University of Ottawa. They provide a comprehensive inventory of decision aids, ratings of the effectiveness of these aids, and provides information on how to get them.

decisionaid.ohri.ca

Although the following sources were created primarily for physicians and policy makers, consumers should not fear consulting them. These are all free.

The U.S. Federal Agency under Health and Human Services, Agency for Healthcare Research and Quality (AHRQ) has a website that summarizes all the available data about treatment for specific conditions (look for EPC Evidence Reports).

ahrq.gov/clinic/epcix.htm

The Drug Effectiveness Review Project (DERP) is a collaboration of public and private organizations developed by the Oregon Health and Science University. It provides comparative data on the benefit, side effects, and costs of different prescription drugs that treat the same problem. This is the course used by the aforementioned Consumer Reports Best Buy Drugs.

ohsu.edu/drugeffectiveness/reports/final.cfm

The National Institute for Health and Clinical Evidence (NICE) is an independent, nonprofit, British organization that advises the British National Health Service. They provides summaries of all the available data about treatments for specific conditions.

nice.org.uk/guidance/index.jsp?action=byTopic

The Physician Data Query (PDQ) is part of the National Cancer Institute. It provides summaries of all the available data about cancer prognosis and treatments.

cancer.gov/cancertopics/pdq

The U.S. Food and Drug Administration (FDA) Center for Drug Evaluation and Research reviews and approves new and generic drugs.

fda.gov/cder/index.html To look up individual drugs, go to accessdata.fda.gov/Scripts/cder/DrugsatFDA/

The U.S. Preventive Services Task Force (USPSTF) is an independent panel of experts sponsored by the AHRQ. They provide recommendations on a wide variety of clinical topics.

ahrq.gov/clinic/uspstfix.htm

 

Health Statistics

February 5, 2010

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, www.ucpress.edu.

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 healthymemory.wordpress.com, 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 healthymemory.wordpress.com with appropriate and specific direction to the original content.

Online Memorials

February 4, 2010

Consider using transactive memory to leave a part of you behind once you have moved on to the hereafter. Consider a conventional memorial that consists either of a headstone marker, indicating the location of your remains, or an urn, enclosing your remains. With today’s technology, you can do considerably better than that. Even if you use traditional means for handling passing on, these means can be substantially enhanced via today’s technology.

The Navy Memorial offers a means of leaving an online memorial for Navy veterans. My Dad, who was cremated, is memorialized there. I find this of great comfort. Any time I am on-line I can visit and renew old fond memories. He was one terrific Dad.

His is a very simple memorial. One can go well beyond this. My Last Email, mylastemail.com, provides for both on-line obituaries and on-line memorials. Other services are bcelebrated.com, wildrosecemetries.com, and memorial2u.com.

These sites provide a means not only of communicating directly with your loved ones, but also of celebrating your life and documenting your accomplishments. Videos and recordings can be included. You can leave behind those accomplishments for which you are most proud. There is always the possibility that some of your work might be discovered and appreciated by later generations.

It is not advised to wait until you are at death’s door before starting this. You can start now, while you’re still healthy. You might find that this exercise will force some discipline on you that will increase your focus and the desire to leave something significant behind.

It did that for me. So long, I need to begin…

© Douglas Griffith and healthymemory.wordpress.com, 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 healthymemory.wordpress.com with appropriate and specific direction to the original content.

Transactive Memory and the Dearly Departed

February 2, 2010

The Washington Post published an interesting article, “Let Online Lives Outlast the Dearly Departed” (Rosenwald, January 25, 2010; A01, or search for the tag “transactive” on delicious.com). With the advance of technology, more and more of our personal information is stored online. Our logons and passwords are stored throughout cyberspace. Included here are bank accounts, stockbroker accounts, insurance accounts and other accounts of considerable importance. This article addressed the issues that arise when your physical being leaves behind only its virtual reality. In the terminology of this blog this information is residing in transactive memory.

The Post article writes of a coming cybercrisis as many Internet services have policies that forbid accessing or transferring accounts, including recovering money without the password. Court orders are usually required to circumvent this requirement. Of course, this assumes that those you left behind know that there are accounts to access. At one time there was a paper trail that could be traced to find these accounts. But should you go the paperless route, there is no paper to trace. The paper trail has gone online.

Of course the simplest way of dealing with this problem is to leave your loved ones with a paper trail leading to these accounts and their passwords. Such a paper trail is risky, however, should it fall into the wrong hands. Legacy Locker, legacylocker.com, provides a means of securing this information in cyberspace. For a fee you can store all your passwords an log-in information. When you pass-on this information will be accessible to whomever you designate as digital executor. Short of passing on, such a resource can be helpful in dealing with less traumatic problems, such as forgetting a password.

Entrustet is part of LinkedIn and provides a variety of services in this area. As do DataInherit, datainherit.com, Parting Wishes, partingwishes.com, and deathswitch.com. If I Die, ifidie.org, is a free service, that will send out an email written by you with all the information you want to pass on.

In all of these services you are employing transactive memory to store information after your biological memory is no longer available to function.

© Douglas Griffith and healthymemory.wordpress.com, 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 healthymemory.wordpress.com with appropriate and specific direction to the original content.

The Availability Heuristic

February 1, 2010

The availability heuristic is the use of information that can be recalled easier.  Perhaps it would be more accurate to call it the accessibility heuristic.  For example, are there more words in the English language that begin with the letter r or have the letter r in the third position in the word?   Most people think that there are more words beginning with the letter r, but in truth r is in the third position in many more words than in the first position.  In attempting to answer this question one tries to recall words.  It is much easier to recall words by their first letter than by their third letter.  Consequently this information is much more available.   Now the accessibility heuristic does have its value.  If you are time constrained, it may provide the only hope of an answer.  However, if there is time, one needs to look it up.

            Here is another example.  Are there more deaths due to homicide than to diabetes-related diseases.  Many would answer homicide to this question.  Homicides are in the news and on television and the movies, whereas diabetes wreaks havoc in relative obscurity. 

            Sticking to the homicide theme, which is higher, the number of homicides or the number of suicides?  In the United States in 2005, there were 5.6 homicides per 100,000 people, but there were 11 suicides per 100,000.  So the suicide rate is almost twice the homicide rate, yet most would probably opt for the homicide rate.  Again, homicides get much more attention than do suicides.  The murder mystery is a genre in literature.  Have you heard of a suicide mystery.   Usually suicide mysteries are whether they are true suicides or whether someone was murdered.

Continuing in this vein, in 2006 were there more deaths attributed to

assault (murder) than to Parkinson’s disease?

More deaths attributed to assault than to influenza and pneumonia?

More deaths attributed to assault than to Alzheimer’s Disease?

More deaths attributed to assault than to chronic lower respiratory diseases?

The answers to all four questions is “no.” But murders make the news. The are highly available. Many more people die every day from other causes, but they are less likely to make the news. Hence, they are less available.

© Douglas Griffith and healthymemory.wordpress.com, 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 healthymemory.wordpress.com with appropriate and specific direction to the original content.