Epidemiology: Disease Patterns, Causes, and Effects

• MED 106 Research Methods and Medical Statistics is an intro to Biomedical Research
• Epidemiology studies the spread, causes, and effects of diseases on populations
• Understanding patterns, causes, and effects of health and disease is involved in epidemiology
• Epidemiologists track outbreaks, identify risk factors, and develop control/prevention strategies
• Epidemiology is essential in public health, guiding policies to protect and improve health
• Statistics provides the tools and methods to collect, analyze, and interpret health data in epidemiology
• Statistics and epidemiology go hand in hand

Historical Milestones

• Hippocrates (400 BC) sought the logic to illness by examining environmental influences on disease
• Hippocrates introduced the terms "epidemic" and "epidemiology"
• He pinpointed diseases occurring in specific places at specific times and introduced 'risk factor' concept
• Hippocrates suggested each disease is caused by different risk factors and wrote 3 articles on epidemiology
• John Snow (1813-1858) was a British physician and the father of modern epidemiology
• Cholera outbreak in London in 1849 resulted in ~15000 deaths
• Snow proposed that people were infected by swallowing "something" that multiplied
• Observation and investigation revealed cholera was more common in areas with polluted river water coming from the Thames
• Conducted an experiment by sealing a water pump in an infected neighborhood
• Cholera disappeared as a result
• Florence Nightingale (1820-1910) was a British nurse, statistician, and the founder of modern nursing
• Nightingale collected and analyzed death data during the Crimean War (1853-1856)
• Most deaths during Crimean War deaths were due to preventable diseases from poor hygiene and not battle wounds
• A new type of chart was presented called the called the Nightingale Rose Chart that resulted in improved sanitary conditions and reduced death rate
• Established the Nightingale Training School of nursing in 1860 at St. Thomas Hospital in London
• Nightingale advocated for sanitary reform, better hygiene practices, and was a pioneer of healthcare data visualization
• Edward Jenner, in 1796, sought to address a smallpox outbreak
• Jenner observed that milkmaids with cowpox were protected from smallpox and hypothesized that exposure to cowpox could protect one against smallpox
• Jenner tested taking material from a milkmaid's cowpox sore and inoculated it into the arm of his gardener's 9 year old son
• He exposed Phipps to variola virus but Phipps never developed smallpox
• James Lind (1716-1794) was a British military surgeon in the Scottish and Royal navies
• British sailors suffered from a devastating disease during long trips where no one could identify the etiology
• Lind observed that sailors consumed a very poor diet lacking in fresh fruits
• Lind gave limes to sailors
• 6 random sailors continued their usual diet and 6 were given 2 oranges & 1 lime/day for 6 days
• Among the latter group, 2 sailors had complete symptoms withdrawal
• Lind conducted the first ‘clinical trial' in 1747, proving scurvy was caused by lack of citrus fruits
• The British Doctors Study began in 1951; led by Sir Richard Doll and Sir Austin Bradford Hill
• 34,000 male British doctors were recruited and asked about smoking habits to be followed
• The relationship between smoking and diseases, particularly lung cancer, was researched
• The British Doctors Study was the 1st large prospective study proving associations between tobacco smoking and lung cancer (1954), myocardial infarction (MI) and chronic obstructive pulmonary disease (COPD) (1956).
• Thomas Bayes (1702–1761) an English statistician who developed Bayes' Theorem
• Bayes' Theorem has become a cornerstone of modern statistics, central to machine learning, epidemiology, and data analysis
• The theorem allows one to revise the probability of an event based on new evidence
• Alan Turing solved the Enigma code in WW2 using Bayes' theorem

Modern use of statistics in Medicine

• Prediction Rules use statistical models (risk scores) to predict patient outcomes
• Machine Learning & AI is used for diagnostic tools (image recognition) and decision support systems
• Health Economics uses cost-effectiveness analyses and statistical models to assess economic impact
• Healthcare providers and policymakers make informed decisions about resource allocation

Scientific method is comprised of 5 steps:

• Observation
• Devise a testable research question
• Formulate a specific research hypothesis
• Test the hypothesis
• Derive a conclusion (accept or reject hypothesis)

Different types of biomedical research

• In vitro studies (lab-based research)
• Studies on animal models (usually rodents)
• Small scale experimental studies on humans
• Large-scale observational epidemiological studies in humans (cross-sectional, case-control, and/or cohort studies)
• Large-scale interventional studies in humans (clinical trials)
• Meta analyses and umbrella reviews

Main purposes of biomedical research

• Evidence-based medicine (EBM) systematically reviews and uses clinical research to aid the delivery of optimum clinical care
• Disease prevention identifies of risk factors and protective factors and enables public health programmes to prevent disease