Chapter Two THE INADEQUACY OF LESSER EVIDENCE Flashcards
What is a significant reason for confusion in the literature regarding coronary artery disease?
The tyranny of a concept or hypothesis that some investigators become overly attached to.
What can happen when presentation of a hypothesis turns into evangelistic fervor?
Progress is stopped and controversy takes over.
What did researchers set out to test from the 1950s onward?
Ancel Keys’s hypothesis that coronary heart disease is strongly influenced by dietary fats.
How did the literature regarding dietary fats and coronary heart disease change by 1977?
It grew to ‘unmanageable proportions’ with conflicting evidence.
What was Jeremiah Stamler’s perspective on the evidence for Keys’s hypothesis?
He believed they had a ‘totality of data’ supporting it, although it was only half the evidence.
What did Thomas Dawber state about the diet-heart relation in 1978?
It was an unproved hypothesis that needed much more investigation.
What was a critical difference in philosophy between proponents and skeptics of Keys’s hypothesis?
Skeptics demanded rigorous scientific evidence, while proponents acted on the belief they had to provide immediate advice.
What did proponents of Keys’s hypothesis believe about treating patients?
They believed patients should be treated as if they already had heart disease to prevent it.
What was the purpose of the National Diet-Heart Study planned in 1961?
To determine if changes in diet could help prevent heart attacks.
What did Keys imply about the absence of final proof for his hypothesis?
It was not evidence that the hypothesis was wrong.
What role did the press play in the dietary-fat controversy?
It favored proponents of the hypothesis, creating a positive feedback loop.
What is confirmation bias?
The tendency to interpret evidence selectively in favor of one’s hypothesis.
What did George Mann conclude about the Masai nomads’ cholesterol levels?
Their low cholesterol levels did not correlate with heart disease, contradicting Keys’s hypothesis.
What did Keys argue about the Masai’s unique cholesterol metabolism?
He suggested they had evolved a mechanism to suppress cholesterol synthesis.
What did the Framingham Heart Study reveal about cholesterol and heart disease risk?
High cholesterol was associated with increased heart disease risk, but the association was not consistent across all demographics.
What did the Framingham investigators note about cholesterol’s predictive value for women over fifty?
Cholesterol had ‘no predictive value’ for them.
What was the outcome of the dietary research from Framingham regarding Keys’s hypothesis?
It failed to support the hypothesis and was not widely published.
What is the importance of rigorous scientific skepticism in research?
It helps prevent selective interpretation and encourages thorough testing of hypotheses.
Fill in the blank: The dietary-fat controversy exemplified the issue of _______ in scientific research.
confirmation bias
True or False: The Framingham Heart Study was published in a medical journal during the early 1960s.
False
What was the main focus of the Framingham Study?
To assess the diet and cholesterol levels of men with high and low cholesterol levels
The study involved interviewing and assessing a thousand local subjects between 1957 and 1960.
What did the Framingham Study reveal about the diets of men with high and low cholesterol?
There was no difference in the amount or type of fat consumed between the two groups
This finding raised questions about the role of diet in cholesterol levels.
What cautionary note was injected into the Framingham Study findings?
The variation in serum cholesterol levels was not explained by diet as measured in the study
This suggests other factors might influence cholesterol levels.
What challenge does the phrase ‘as measured here’ represent in scientific investigation?
It highlights the difficulties in accurately measuring dietary intake and its relationship to health outcomes
It reflects the limitations in establishing causal relationships.
What was a common conclusion of multiple studies regarding diet and heart disease?
Most studies failed to reveal a correlation between fat consumption and cholesterol levels or heart disease
This included studies from various locations such as Puerto Rico, Honolulu, and Chicago.
What did proponents of Keys’s theory argue regarding homogenous diets?
They believed that too similar diets made it difficult to show that fat was responsible for heart disease
They suggested comparing populations with differing fat intakes.
Who cautioned against the tendency to reject conflicting evidence in scientific research?
Sir Francis Bacon
He emphasized the importance of treating all evidence equally.
What were the two sides in the dietary-fat hypothesis debate characterized by?
Proponents focused on positive evidence while skeptics were concerned with negative evidence
This led to polarized views and difficulty in discussion.
What was the outcome of the Western Electric Study after reanalysis?
The reanalysis found no significant association between saturated fatty acids and coronary heart disease
It challenged Keys’s hypothesis.
What did Stamler and Shekelle believe about their ambiguous results?
They believed their results should align with previously positive studies supporting Keys’s hypothesis
They interpreted their findings through the lens of existing literature.
What was the primary component of cell membranes that could be affected by dietary fat composition?
Fat, specifically in the form of myelin
Changes in dietary fats could alter cell membrane permeability.
What is the Seven Countries Study known for?
It is considered Ancel Keys’s masterpiece in understanding diet and heart disease
It included diverse populations to study the effects of diet on heart disease.
What were the three lessons taught by the Seven Countries Study according to Keys?
- Cholesterol levels predicted heart disease risk
- Saturated fat predicted cholesterol levels and heart disease
- Monounsaturated fats protected against heart disease
These conclusions influenced dietary recommendations.
What flaw did the Seven Countries Study have according to critics?
Keys selected countries that would support his hypothesis rather than choosing randomly
This selection bias may have skewed the results.
What did Keys and his colleagues discover about total mortality in their later analysis?
High cholesterol did not predict increased mortality despite its association with heart disease
They realized coronary heart disease accounted for less than one-third of all deaths.
What misconception about dietary advice emerged from the Seven Countries Study?
That eating like the Japanese was the best dietary advice for heart disease prevention
The study’s findings suggested otherwise.
What is the primary challenge of using epidemiologic tools to study chronic diseases?
Epidemiologic tools were primarily developed for infectious diseases, making them less effective for chronic conditions like heart disease
Establishing causation for chronic diseases is more complex.
Who demonstrated the connection between contaminated water and disease in 1854?
John Snow
What is a major challenge in establishing the causes of chronic diseases?
The subtler causes are difficult to elucidate
What is the relationship between cigarette smoking and lung cancer?
Smokers are thirty times as likely to get lung cancer as nonsmokers
What methodology did early investigators use to establish causes of chronic diseases?
Accumulating diet and disease data in populations and using statistical analyses
What did Raymond Pearl state about epidemiological data?
It fails to reliably establish causes due to bias and quality issues
What did John Bailar explain about statistical associations in epidemiological studies?
They are subject to many interpretations due to complex variables
What is the only reliable way to establish cause and effect in medical research?
Controlled experiments or controlled trials
What is the purpose of using placebos in drug trials?
To avoid distortion in comparing treatment effects
What does ‘double-blind’ mean in clinical trials?
Neither subjects nor physicians know which pills are placebos
What are double-blind, placebo-controlled clinical trials considered in medicine?
The gold standard for research
Why are diet trials particularly challenging to conduct?
It’s impossible to use placebos or a double-blind method
What was the conclusion of the two trials that studied low-fat diets on heart disease rates?
One concluded it reduced rates; the other concluded it did not
What was the dietary restriction in the British trial studying low-fat diets?
Restricted to 1.5 ounces of fat per day
What was the outcome of the British trial regarding heart disease recurrence?
Recurrence was identical in both control and experimental groups
What was the main focus of the Anti-Coronary Club Trial?
The ‘prudent diet’ to reduce heart disease
What did the Anti-Coronary Club Trial incorrectly conclude about the prudent diet?
It linked the diet to a decrease in heart disease despite mortality issues
What was a significant finding of the Minnesota Coronary Survey?
The cholesterol-lowering diet was associated with increased heart disease rates
What did Seymour Dayton question about high unsaturated fat diets?
Their potential noxious effects over long periods
Which trial seemed to demonstrate a benefit from a high-polyunsaturated, low-saturated-fat diet?
The Helsinki Mental Hospital Study
What was a notable limitation of the Minnesota Coronary Survey?
Results were unpublished for sixteen years due to disappointment
What is necessary to determine if an intervention in preventive medicine is successful?
It must cause more good than harm
What did the 2002 findings regarding hormone-replacement therapy reveal?
It seemed to do more harm than good
What is the significance of controlled trials in dietary recommendations?
They are essential to establish long-term health benefits and risks
What therapy did the FDA first approve in 1942?
Hormone replacement therapy (HRT) for the treatment of hot flashes and night sweats.
What did observational studies report about hormone replacement therapy before the 1990s?
It dramatically reduced the incidence of heart attacks.
What was the purpose of the Women’s Health Initiative launched by the NIH in the 1990s?
To conduct the first large-scale, double-blind, placebo-controlled trial of hormone-replacement therapy.
How many women were involved in the NIH’s Women’s Health Initiative trial?
Sixteen thousand healthy women.
What were the findings regarding heart disease and hormone replacement therapy?
Heart disease, breast cancer, stroke, and dementia were more common in women prescribed hormone replacement.
Who described the inadequacy of lesser evidence in medical studies?
Epidemiologist David Sackett.
What did David Sackett criticize in his 2002 editorial?
Medical authorities advocating unproven preventive measures without validation from rigorous randomized trials.
What was the intended study related to the diet-heart controversy starting from 1960?
The National Diet-Heart Study.
Who predicted that the National Diet-Heart Study would take five to ten years to complete?
Jeremiah Stamler.
What did the committee led by Pete Ahrens conclude about the diet-heart hypothesis in 1969?
It was not known whether dietary manipulation had any effect on coronary heart disease.
What was the estimated cost for a definitive test of the diet-heart hypothesis?
Perhaps $1 billion.
What did the NIH agree to fund instead of a large trial?
Two smaller trials costing $250 million.
What were the two smaller trials funded by the NIH intended to test?
- Cholesterol-lowering drugs to prevent heart attacks
- A combination of cholesterol-lowering diets, smoking-cessation programs, and blood pressure-reducing drugs.
What did the results of the reanalysis of a 1964 study comparing Dubliners and Boston Irish indicate?
Men eating the most saturated fat had slightly higher heart-disease rates, but results were weakly supportive of the diet-heart hypothesis.
What was the significant finding in the autopsies conducted by Dayton and colleagues?
No difference in the amount of atherosclerosis between men on different diets.
What changes were made to ordinary milk and margarine in the diet studied?
- Ordinary milk was replaced with soybean oil emulsion in skim milk
- Butter and margarine were replaced with margarine made of polyunsaturated fats.
What did the Heart and Estrogen/Progestin Replacement Study find regarding hormone replacement therapy?
No benefit from hormones and an increased risk of heart disease for the first few years.
What was Frantz’s Minnesota Coronary Survey related to?
It was a pilot project for the National Diet-Heart Study.
