hsci

• Epidemiology


  The study of the distribution and determinants of health related states in specified populations and the application of this to study to control health problems
• Epidemiology


  • Distribution - occurrence of cases by time, place and person
  • Determinants - all the causes and risk factors for the occurrence of a disease, including physical, biological, social, cultural, and behavioural factors
  • Health related states - Diagnosis of a specific disease or cause of death, Health-related behaviour (eg. smoking, taking prenatal vitamins)
  • Specified population - a measurable group defined by location, time, demographics, and other characteristics
  • Application - Analysis, conclusion, distribution, and timely use of epidemiologic information to protect the health of the population
• Miasma


  Bad vapour in air (one of the two theories about cholera)
• Germ theory


  Small organism responsible (one of the two theories about cholera)
• John Snow's investigation of cholera

  1. Documenting the source of the drinking water for people dying from cholera - natural experiment referred as his "Grand Experiment"

  2. Demonstrated that contaminated water was the key source for cholera

  3. Came up with the idea which company is coming up with the drinking water by determining the saltiness of the water. He goes door to door asking them the source of their water to map it out.

  4. Experiment 1: looks at who on what side of the street. What side of the road depends if you will get cholera. Sewage water went toward the water well, everyone on that side of that street got cholera and the side where sewage water goes away from the well, only one person got cholera.

  5. Experiment 2: broad street, expected cases vs actual cases

  6. Experiment 3: sampling water supply of household to determine where its coming form

  7. Came to the conclusion that most deaths happened near the Broad Street pump. Removed the handle of the pump to stop the outbreak so people won't drink the water and get cholera.
• Toxic Shock Syndrome


  Associated with menstrual periods, Cases more likely to use tampons, Case-control study: women who use RELY tampons 8X more likely to get TSS, Staphylococcus organism, Rare outcome + common behaviour
• How they determined the brand of tampons

  They figured out the cause by a survey to see who uses which brand, Placed a warning paper inside the box fo the tampon to tell people the risk of toxic shock syndrome
• Application of Epidemiology: 1. Identifying the cause of a new syndrome, 2. Assessing risks of exposure, 3. Determining whether treatment "x" is effective, 4. Identifying Health Service Use Needs and Trends, 5. Identifying Practical Prevention Strategies
• The Epidemiologic Approach


  • Counts cases or health events, and describes them in terms of time
  • Divides the number of cases by an approach denominator to calculate rates (morbidity and mortality)
  • Compares these rates over time (trends) or for different groups of people
• Endemic


  Cases are continually occurring in the population
• Epidemic


  Outbreaks of a disease in a localized group of people; more cases than expected, spread by vectors, carriers, or sudden intro of new pathogen
• Pandemic


  Epidemics that have spread beyond their local region and are affecting people in various/all parts of the world
• E.coli


  Bacteria that live in cattle and other animals, Usually transmitted to humans through food, Cause cramps and diarrhoea that can be bloody, Can lead to kidney failure and death, About 150 cases/year in BC
• Observational Studies


  Researcher does not intervene in any way, Measurement if occurrence of disease or health outcome, Comparing patterns of exposure and disease outcomes, Identifying risk factors associated with health/disease
• Experimental Studies


  Investigator tries to change something and measure the effect on disease outcome-clinical trials, preventative trials
• Descriptive Studies


  • Case reports/case series - detailed descriptions usually by a doctor or a group of doctors identifying diseases that are unusual/interesting; may be related to unusual exposure
  • Routine data - Mortality, life expectancy, Prevalence surveys, Migrant studies
• Analytical Studies


  Primary purpose is to evaluate the association between an exposure or characteristic and the development of a particular disease
• Exposure


  Can include: Infectious agents, Behaviours, Intrinsic Characteristics of Individuals, Social or Environmental Factors
• Ecological Studies


  Compare the prevalence of exposures and disease occurrence in populations
• Cross-Sectional Studies


  Study group chosen to representative of a subgroup of society /cross-section of the population
• Case Control Study


  Choose individuals with disease or outcome of interest (cases) and a comparison group without the disease (controls), Multiple ways for selecting the control group, Comparison is the odds of exposure
• Prospective Cohort Studies


  Follow up studies: follow up people over time to see what happens, Compare rates if occurrence of disease in people with or without a particular exposure
• Important Findings from Smyth (2015): Current drinking associated with a reduced risk of MI, Current drinking associated with an increased risk of alcohol related cancers and injury 'high alcohol intake associated with increased mortality, There are different associations between alcohol and these outcomes, depending upon the level of income in the region
• Rationale and Research Questions

  Study: Cocoa Intake, Blood Pressure, and Cardiovascular Mortality, Rationale: Cocoa consumption may improve CVD outcomes, Small studies had documented improvements in: Blood pressure, Endothelial function, Insulin sensitivity, Research questions: what about habitual consumption in a group of the population at high risk for heart disease?
• Methods


  Elderly men in netherlands, Cohorts of men (n=939); after exclusions (n=470), Measured: Intake of cocoa products, Systolic and diastolic BP, Cholesterol levels, History of MI, angina, heart failure, diabetes, cancer, Physical activity, Cigarette use, Prescription medication and aspirin use
• Are Female Hormones Protective against CVD?: Widespread use of HRT since 1960s, Observational studies from 1980s and 1990s suggested protective benefit of HRT on CVD, 2002 Women's Health Initiative RCT Findings: HRT use increased the risk of CVD + increased risk of breast cancer, Result: decreased use of prescriptions + decreased marketing by pharmaceutical companies
• Rationale for Study


  Use of aspirin in primary prevention remains controversial, CVD a leading cause of death in women, Sex-based differences in salicylate metabolism, Lingering uncertainty: hormone replacement therapy and risk of cardiovascular disease in 2005, risk of hemorrhagic stroke and potential differences in risk between men and women
• Methods - How did they do the study

  RCT: randomized control trial evaluating effectiveness of low-dose aspirin and Vitamin E in primary prevention of CVD and cancer, Women >45 years, No history of CVD, Not taking/willing to forgo use of NSAIDs, No vitamin supplements of Vitamin A, E, or beta-carotene
• Results: In which group of women was the use of the aspirin most beneficial? Women aged 65 and older, Were there any side effects reported? Yes, bleeding and ulcers, Did the use of hormone replacement therapy modify the effects or aspirin? No
• HIV/AIDS pandemic: Very contagious virus that infected a lot of people and died, Affects the immune system, Fast replicating and several mutation, is the reason we don't have a vaccine today, Transmitted through bodily fluids, Came from an animal being eaten and then spreaded
• Global estimates for children under 15 years old


  • Children living with HIV: 1.5 million cases
  • New HIV infections: 130,000
  • Deaths due to AIDS: 84,000
• Global estimates for Adults and children

  • People living with HIV: 39 million
  • New HIV infections: 1.3 million
  • Deaths: 630,000
• Most cases, deaths and new infections are in eastern and southern Africa, About 3600 new HIV infections (adults and children) a day as of 2022, About 50% are in sub-Saharan Africa, About 360 are among children under 15, About 3200 are among adults ages 15 years and older, of whom: Almost 46% are among women, About 30% are among young people (15-24), About 18% are among young women (15-24)
• By 2007 12 millions orphans in Sub Saharan Africa
• People living with HIV accessing antiretroviral therapy (as of 2022)

  • By end of 2022, 29.8 million people were accessing antiretroviral therapy
  • 82% of women aged 15 years and older had access to treatment however just 72% of men aged 15 and older had access
  • 82% of pregnant women living with HIV had access to antiretroviral medicines to prevent transmission of HIV to their child
  • 9.2 million people living with HIV did not have access to the antiretroviral treatment in 2022
• Prevalence


  The proportion of individuals in a population with the disease at a given point in time, No units, Can be reported as a proportion or percentage (multiple prevalence by 100), Can be reported as cases or population, Must report the time period at which people are counted
• Prevalence = number of cases of disease / total population
• 72% of men aged 15 and older had access to treatment
• 82% of pregnant women living with HIV had access to antiretroviral medicines to prevent transmission of HIV to their child
• 9.2 million people living with HIV did not have access to the antiretroviral treatment in 2022