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Animals in Scientific Research
Science of the Future - Epidemiology
From Drs. Ray and Jean Greek in their book, Specious Science (please refer to the book for source material).
Epidemiology is the field of research that studies the distribution of diseases in populations, as well as the factors that influence the occurrence of disease. Epidemiologists study epidemics, which are outbreaks of disease that attack a large number of people at about the same time, and endemic diseases, which are diseases that exist permanently in a region.
The field of epidemiology is based on the premise that most diseases, rather than occurring randomly, are related to environmental and personal characteristics that vary by place, time, and subgroup of the population. Epidemiologists study the environmental and personal characteristics of people to determine how these impact on disease occurrence. These studies can yield a tremendous amount of information, including:
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Determining who is most likely to develop a particular disease. -
When the disease is most likely to occur. -
The pattern of disease occurrence over time. -
What type of exposure its victims have in common. -
How much exposure increases the rate of disease occurrence. -
How many cases of the disease could be prevented by eliminating the exposure.
It was epidemiology that provided the link between cholesterol and heart disease, smoking and heart disease and cancer, high blood pressure and stroke, diet and cancer and heart disease, environmental factors and cancer, and folic acid deficiency and spina bifida. Epidemiological studies have exposed environmental poisons, revealed causes of birth defects, and led to the abandonment of the practice of bloodletting. In addition, epidemiology has also shown how communicable diseases such as cholera and measles are transmitted, as well as how the HIV virus, which causes AIDS, is spread.
From What Will We Do if We Don’t Experiment On Animals? By Drs. Ray and Jean Greek (please refer to the book for source material).
As stated above, epidemiology is a field of research that involves the study of the distribution of diseases in populations and the factors that influence the occurrence of disease.
It is based on the premise that most diseases do not occur randomly, but are related to environmental and personal characteristics that vary by place, time, and subgroup of the population. Epidemiologists study epidemics, which are outbreaks of disease involving large numbers of people at about the same time. They also study endemic diseases, which are diseases that exist permanently in a particular region or among a particular population. In addition to conducting observational studies, epidemiologists also conduct experimental studies by altering the behavior, exposure, or treatment of people to determine how these alterations impact on disease occurrence.
Epidemiological studies, both observational and experimental, can increase scientists’ understanding of disease by:
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Determining who is most likely to develop a particular disease. -
When the disease is most likely to occur. -
The pattern of disease occurrence over time. -
What type of exposure (such as exposure to an industrial chemical) the victims of a disease have in common. -
How much exposure increases the rate of disease occurrence. -
How many cases of the disease eliminating the exposure could prevent.
As mentioned earlier, the Framingham study linked cholesterol to heart disease, but epidemiological studies have also made a number of other significant contributions to medical science. Epidemiology was in part or in whole responsible for:
- Discovering the ill effects of using diethylene glycol in early antibiotic preparation.
- Linking drugs to the side effects that resulted in their being relabeled or recalled.
- Discovering the cause of scurvy.
- Stopping the practice of bloodletting.
- Discovering the link between folic acid deficiency and spina bifida.
- Revealing the cause and effect relationship between smoking and cancer.
- Linking heart disease and cholesterol.
- Linking high blood pressure and stroke.
- Linking high blood pressure and heart disease.
- Linking repetitive motion and carpal tunnel syndrome.
- Linking smoking and heart disease.
- Linking glass fibers and cancer.
- Linking dietary fat and cancers of the colon and prostate.
- Linking laundry and dry cleaning industries with cancers, and so on.
- Linking environmental poisons produced by industrial chemicals with occupational diseases e.g., coal dust and black lung disease, cotton dust and byssinosis, phosphorous poisoning in munitions workers, silicosis in sandblasters, mercury poisoning in felt workers, and carbon monoxide poisoning in steel workers.
- Finding the cause of building-related illnesses such as Legionnaires' disease and Pontiac fever.
- Finding the association between diet and cancer.
- Linking obesity to cancer of the stomach and esophagus.
- Revealing that a diet high in fiber and vegetables is protective against colon cancer.
- Showing that women who do not smoke, but who live with men who do smoke, have a 50 percent greater incidence of lung cancer than women who live with non-smokers.
- Identifying the cause and mode of transmission of AIDS.
Revealing that a sexually transmitted virus probably causes some anal cancers and that using a condom could prevent them. - Revealing that cumulative exposure to sunlight and vitamin C deficiency could lead to cataracts.
- Demonstrating that obese women have a two-to-fourfold increased risk of having a stillborn baby.
- Revealing an increased risk of death and birth defects in fetuses whose mothers lived on or near farms where such pesticides as phosphates, pyrethroids, halogenated hydrocarbons, carbamates, and endocrine disruptors were sprayed.
- Confirming that exposure to cigarette smoke increases the incidence of middle ear disease, asthma, bronchitis and wheezing illnesses in children, as well as umbilical cord blood mutations.
- Revealing that babies born to women who smoke, or to women exposed to passive cigarette smoke, can have carcinogens in their body at birth and gene mutations that may lead to leukemias and lymphomas.
- Proving that smoking decreased uptake of vitamin C.
- Showing that women who gain weight after reaching adulthood are at an increased risk for breast cancer.
- Finding a high incidence of acute myelogenous leukemia in jet pilots, perhaps due to exposure to cosmic radiation.
- Revealing that men who are exposed to high levels of lead are at increased risk of fathering pre-term infants.
- Revealing that mercury produces birth defects including developmental delays and mental retardation.
- Linking low birth weights of babies to cerebral palsy, retinopathy of prematurity, respiratory distress, autism, epilepsy, and other conditions.
- Linking maternal rubella and birth defects.
- Linking most the known causes of birth defects to the condition.
- Linking many genes to the illness associated with them.
- Revealing how most infectious diseases are transmitted.
- In a population-based, matched case-control study, researchers in Stockholm discovered that the risk of early spontaneous abortion is significantly increased in women with low plasma folate levels.
- By studying the DNA of 61 pairs of siblings who had had heart attacks, scientists found three clusters of genes linked to heart attacks.
- By studying 718 families with more cases of breast cancer than would be expected just by chance, scientists were able to locate a mutation in the CHEK2 gene associated with an increase for the risk of breast cancer in both women and men.
- Researchers conducting a meta-analysis of studies in the UK, Denmark, France, and other countries on the association between polymorphisms and type II diabetes found that a single nucleotide polymorphism predisposes to type II diabetes.
Epidemiology is used to identify increases and decreases in the incidence of disease. For example, a study of data from 3,050 pediatric head and neck cancers that were reported to the US National Cancer Registry between 1973 and 1996 revealed that the incidence of these cancers among children younger than 15 years old rose 35 percent from 1973 to 1975 and from 1994 to 1996.
Epidemiology continues to shed light on factors that increase risk of disease.
One study revealed that toxic chemicals pose an elevated cancer risk in two-thirds of Americans. By studying 32 toxic chemicals, including those emitted from automobiles, power plants, and other industries, scientists discovered that the chemicals cause 10 additional cancers for every one million people.
Researchers used data from 898,835 women enrolled in a randomized, controlled trial of screening for breast cancer to examine the association between smoking and breast cancer risk. It was found that long duration, high-intensity smoking is a breast cancer risk, and that those who smoked for at least 40 years and at least 20 cigarettes per day had the highest risk for breast cancer.
DDT (dichlorodiphenyl trichloroethane), the poison brought to the attention of the general public by the environmentalist Rachel Carson, was once thought to cause breast cancer, based in part on studies in animals. But epidemiological studies have failed to confirm this.
However, findings from a study conducted by geographers and epidemiologists at the University of Buffalo have shown that women who developed breast cancer were more likely to have lived closer together at birth and at menarche, a concept called clustering, than women who didn’t develop breast cancer. The findings indicate that there may be something in the environment close to these clusters that influences a woman’s breast cancer risk, according to Joe Freudenheim, Ph.D., professor in the Department of Social and Preventive Medicine in the University of Buffalo School of Medicine and Biomedical Sciences and senior author of the study.
These studies, and many others demonstrate how often research methodologies overlap, since these studies incorporated both epidemiology and in vitro technology.
Epidemiology has also revealed factors that reduce the incidence of disease. For example, the largest epidemiological study ever conducted in North America of a childhood nervous system cancer known as neuroblastoma suggests that women who take multivitamins during pregnancy can cut their children’s risk of the tumor by 30 percent to 40 percent.
In another classic epidemiological study, scientists analyzed data from the parents of 72 infants with nonsyndromic omphalocele (a birth defect where the infant is born with a hernia at the navel) and compared data from the parents of 3,029 infants without birth defects born in Atlanta between 1968 and 1980. The researchers discovered that maternal use of a multivitamin was linked with a lower omphalocele risk. This means that women who use multivitamins around the time of conception may be less likely to have an infant with omphalocele than women who do not use them.
An epidemiological study of 209 men with prostate cancer and 228 control subjects revealed that men with high levels of lycopene (a nutrient found in tomatoes) in their blood appear to be at a lower risk for prostate cancer than men with low levels.
Epidemiology has also led scientists to more effective treatments for disease. By studying the records of 212 children who were diagnosed and treated for Hodgkin’s disease between 1970-1994, scientists in India found that use of cyclophosphamide instead of nitrogen mustard in chemotherapy regimens resulted in a low incidence of second malignancies. In fact, no cases of secondary hematologic malignancies were seen in a 25-year follow-up of these children.
By studying 538 patients infected with HIV subtype A to those of 507 patients infected with HIV subtype D, scientists discovered that HIV subtype D is linked to faster disease progression than A in Uganda. The scientists told Reuters News, “If the envelope region [of the virus] plays a major role in pathogenicity, this information may be important in vaccine research and therapeutic interventions.”
By studying the genetic make-up of a family in which 8 of the 20 members demonstrated high bone density, a thickened mandible, and other bones, scientists were able to determine that the gene for the LDL receptor-related protein 5 (LRP5) appears to result in high bone density. This could have important implications for the treatment of osteoporosis. In vitro studies were then conducted that showed that the LRP5 mutation allowed the unopposed activation of a key bone formation pathway.
Epidemiology continues to make significant contributions to our understanding of the aging of our mental ability. In a population-based study, researchers from the University of Edinburgh collected data on 466 surviving subjects, without signs of dementia, from the Scottish Mental Survey of 1932. They found that individuals with the apolipoprotein (APOE) epsilon4 gene fare worse in cognitive testing at 80 years of age compared with similar subjects who do not have the gene
Epidemiology has always been a very sound gauge for determining the sources of disease. Not surprisingly, many of the causes are work-related. A fairly recent hazard is flock, which is the dust from short nylon fibers. Flock workers glue fibers onto fabric to produce a velour look. Injured lung tissue and inflammatory reaction characterize the ensuing disease, known as “flock worker’s lung.”
These, and other cases we cite, are examples of epidemiology. However, some would classify them as clinical research, which demonstrates that human-based research crosses into many areas. Epidemiology is closely related to clinical research. As Lawrence K. Altman, MD, medical correspondent for The New York Times, professor at the New York University Medical School, a Master of the American College of Physicians, the American College of Epidemiology and the New York Academy of Medicine, and a member of the Institute of Medicine of the National Academy of Sciences, explains:
“If those goals—curing AIDS, cancer and other diseases—are to be realized, human experimentation will continue to be mandatory since medical progress hinges on learning how humans respond to cutting edge therapies.” Further, he asserts, “More people will come to recognize that ultimately the right animal in experiments designed to advance our knowledge of human diseases must be human. And they will realize the obvious fact that someone must be the first volunteer.”
MC Reade and JD Young wrote in the British Journal of Anaesthesia:
As a result, the bulk of the literature investigating the pathogenesis of septic shock uses rodent models, or isolated or cultured cells. Therapeutic advances based on this research may well promise new hope for owners of rats requiring intensive care, but there is increasing evidence that human sepsis may be a fundamentally different disease. Conclusions based on animal models may not be applicable to humans. While accepting that there are ethical and practical limitations on the scope of human studies, to not do this runs the risk of developing excellent treatments for rat sepsis that are of no use to humans at all.
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