Epidemiology of Chronic Diseases I

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Epidemiology of Chronic Diseases I
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• There is never a single right solution. There are
  aways multiple wrong ones, though.
• Akin's Laws of Spacecraft DesignDave Akin,
  Professor, University of Maryland

• Amen
• Marions corollary

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Prevention of Cancer
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• Major sources for this section
• Canadian Cancer Statistics 2005
• Progress Report on Cancer Control in Canada (c.
  2004)

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Definition

• A complex family of neoplastic diseases
  characterized by aberrations of cellular growth
  that causes abnormal proliferating cells to
  invade or destroy normal tissue

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Epidemiology

• Leading cause of premature death in Canada
• Both males and females
• Expected to overtake cardiovascular disease as
  leading cause of death in Canada in a few years

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• Approximately 50 of all cancer incidence is
  related to preventable causes
• Most common cancers
• Lung
• Prostate
• Breast
• Colorectal

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• These 4 account for 56 of all cancers
• Most commonly diagnosed cancers by sex
• Males prostate cancer
• Females breast cancer
• Highest percentage of deaths
• Lung cancer both sexes

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• Cancer incidence appears to be on the increase
  .. However
• Age-standardized cancer incidence in males is
  declining slightly
• In females, still rising slightly
• Lung cancer

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• In children, rising
• Incidence higher in 0-4 15-19 age groups
• Different cancers than in adults
• Leukemia
• Brain tumours
• Lymphomas
• Sarcomas

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• These cancers not yet conceptualized as
  preventable
• Environmental exposures under increasing scrutiny
• Death rates for cancer are fairly stable

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• Geographic variations in cancer incidence
• Incidence mortality higher in Eastern Canada
• Incidence of smoking also higher in Eastern Canada

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• Approx. 41 of Canadians will develop cancer over
  their lifetime
• 38 of women
• 44 of men
• Approx 1 in 4 Canadians will die of cancer
• 24 of women
• 29 of men

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Risk Factors for Cancer

• Non-modifiable
• 1. Age
• Cancer risk increases with age
• 44 of incidence in those over 70
• 60 of mortality in those over 70

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• 2. Sex
• Cancer mortality rates for females higher than
  for males during reproductive years
• Otherwise, higher for males

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• 3. Genetics/Race
• Some cancers more frequent in specific racial
  groups
• Difficult to disentangle impact of
• Socioeconomic status
• Dietary patterns
• Employment patterns
• Environmental exposures
• Genetics

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• Modifiable
• Fundamental concepts
• Exposure
• The state of being exposed to something harmful
• In the case of cancer, of being exposed to a
  known or potential carcinogen

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• Mechanisms of carcinogen effects
• Metabolism (chemical)
• Either initiate or promote cellular aberrations
• Effects can be additive or exponential
• Viral
• Interfere with DNA replication

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• 1. Smoking
• Strong causal link between smoking cancer
• Responsible for 27 of all PYLL due to cancer

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• 2. Diet
• Diet-related factors account for 30 of cancers
  in developed countries
• Role of specific nutrients or food groups still
  unclear

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• Believed that high fruit vegetable intake is
  protective
• Believed high meat intake increases risk

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• Believed that high fat intake increases risk
• Increasing fruit vegetable intake may be more
  effective than simply decreasing meat fat
  intake
• Type of fat consumed also important
• More effective to reduce saturated fats

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• Role of non-nutritive dietary intake also unclear
• Additives
• Substitutes
• Residues

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• 3. Activity levels
• Reduces the risk of specific cancers
• 40 reduction in risk for colon cancer
• 30 40 reduction in risk for breast cancer
• 10 30 reduction is risk for prostate cancer
• Insufficient evidence (as yet) for other sites

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• Confers direct and indirect benefits
• Maintains healthy body weight
• Excess weight increases amounts of circulating
• Estrogens
• Androgens
• Insulin
• Increases gut motility (reduces exposure to
  potential mutagens)

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• 4. Microbes
• 15 of cancers world-wide related to
• a) Human papillomavirus (HPV)
• Now considered the necessary cause for cervical
  cancer
• HPV found in tissues of 90 of cases

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• b) Herpes 2
• Associated with greater risk for
• Cervical cancer
• Prostate cancer
• c) Hepatitis B virus
• Associated with up to 80 of all cases of liver
  cancer world-wide

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• 5. Alcohol Consumption
• Increases risk of cancer at several sites
• Mouth, pharynx, larynx esophagus
• Interacts with tobacco
• Liver
• Stomach
• Breast (females)
• Colorectal (males)

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• Risk increases with increased consumption

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• 6. Sun exposure
• Related to UV radiation
• Increases risk for
• Basal cell carcinoma
• Squamous cell carcinoma
• Melanoma

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• The first 6 risk factors are those listed by
  Health Canada and the Canadian Cancer Society
• Indicates a highly behavioural/health education
  approach to cancer control

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• Others would add 2 more risk factors
• 1. Occupational exposures
• 2. Environmental exposures
• These will be further discussed in a subsequent
  lecture

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• Known Possible Risk Factors by Site
• 1. Lung Cancer
• Tobacco
• 2nd hand smoke
• Ionizing radiation
• Radon exposure
• Occupational exposures (specific chemicals)

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• Insufficient fruit/vegetable consumption
• Air pollution

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• 2. Breast Cancer
• For females
• Age
• Family history of breast cancer
• Atypical breast hyperplasia
• High education attainment
• High socio-economic status

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• Prolonged exposure to estrogen
• Early menstruation
• Late menopause
• Null parity
• First child born after age 30
• Post-menopause estrogen progestin use
• Obesity after menopause

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• Excessive alcohol consumption
• Dietary fat
• Ionizing radiation
• Physical inactivity

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• For males
• Age
• Family history
• Radiation exposure
• High estrogen levels
• Genetic
• Therapeutic
• Gynecomastia
• Obesity

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• Prostate cancer
• Prostatic hyperplasia
• Family history
• High fat diet
• Obesity
• Hormonal factors

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• Herpes 2 infection
• Smoking
• Alcohol
• Physical activity
• Race(?)

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• Colorectal Cancer
• Family history
• Inflammatory bowel disease
• High fat, low fibre/vegetable/fruits diet
• Physical inactivity
• Alcohol consumption
• Obesity
• Smoking

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Primary Prevention

• Behavioural Interventions
• 1. Smoking cessation

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• 2. Dietary Intake
• Focus on
• Low fat with emphasis on non-saturated fats
• Moderate meat intake
• High intake of fruits, vegetables and other high
  fibre sources

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• 3. Increase physical activity
• 30 min. of moderate physical activity/day or
• 60 min. of light physical activity/day
• In other words, you dont have to be a track star

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• 4. Avoid infections
• All 3 viruses implicated in cancer etiology are
  sexually transmissible
• Other routes of infection
• Needle puncture (Hep B)
• Perinatal (Hep B)
• Contaminated blood supply (Hep B)
• Non-sexual contact (HPV, Herpes 2)

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• 5. Low - moderate alcohol consumption
• Heavy drinking defined as having 5 or more drinks
  on one occasion 12 or more times/yr.
• 6. Limit sun exposure
• Sunscreen
• Avoiding peak UV exposure

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• 7. Avoidance of occupational exposures
• 8. Avoidance of environmental exposures

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• But is it this simple?
• Why is it that being poor is associated with a
  higher risk of developing cancer (and
  cardiovascular disease diabetes for that
  matter)?

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• Other approaches to primary prevention are also
  needed
• These approaches less amenable to individual
  control
• Require interventions at the economic, social,
  political level
• Will be discussed further in upcoming classes

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Secondary Prevention

• Screening
• 1. Cancer of the cervix
• Pap smear
• 2. Breast cancer
• Breast self-examination (BSE)
• Clinical breast examination (CBE)
• mammography

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• 3. Testicular cancer
• Testicular self-examination
• 4. Endometrial cancer
• Pap smear
• 5. Lung cancer
• Occupational smoking history

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• 6. Colorectal cancer
• Digital rectal examination (DRE)
• Occult blood
• Colonoscopy
• 7. Prostate cancer
• DRE
• Prostate specific antigen (PSA)
• Transrectal prostatic ultrasonography (TRUS)

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Prevention of Cardiovascular Disease
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• Major source for this section
• The Growing Burden of Heart Disease Stroke in
  Canada 2003

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• Identify the major modifiable and non-modifiable
  risk factors associated with CVD
• Identify and discuss primary secondary
  preventive strategies to reduce the incidence of
  CVD

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Definition

• Disease related to the heart and blood vessels
• Atherosclerosis of coronary arteries
• Myocardial infarction (MI)
• Angina
• Hypertension

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Epidemiology

• Leading cause of death in Canada
• Major cause of hospitalization
• Treatment consumes 11.6 of health care spending
• Also causes 15.4 of total indirect costs
  associated with illness

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• Significant impact on quality of life
• 38 report pain
• 59 report activity limitation
• 29 report employment has been affected

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• 8 out 10 Canadians have at least 1 risk factor
  for CVD
• 5.7 of Canadians report living with CVD
• Prevalence rises with age
• Many develop CVD in mid-life
• 25 of those over age 75 report living with CVD

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• Age-adjusted mortality rates have declined since
  1960s
• Result of
• Lifestyle changes
• Better treatments

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• Prevalence has increased
• Regional variations in incidence prevalence
• Newfoundland reports highest
• Lowest in PEI, Canadian north

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Risk Factors for CVD

• CVD considered to be largely preventable in the
  sense that a great deal is known about its
  etiology and risk factors
• The same cannot be said for cancer

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• Risk for CVD is increased by presence of other
  treatable disease conditions
• 1. Increased serum lipids
• Risk associated with elevated a) cholesterol, b)
  low density lipoprotein (LDL), and c)
  triglyceride levels
• Prevalence of elevated serum lipid levels
  increases with age

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• 2. Hypertension
• Defined as
• Systolic BP gt 140 or
• Diastolic BP gt 90
• Increases risk for CVD 2 to 3 fold
• Prevalence increases with age

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• Associated with
• Excess weight
• Physical inactivity
• Heavy alcohol use
• Excess salt intake
• Prevalence in Canadian population 22
• Diagnosed and treated 13

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• 3. Diabetes
• Increases incidence of CVD
• Adversely influences outcome of CVD

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• Non-modifiable Risk Factors
• 1. Age
• Data presented in epidemiology section
• 2. Sex
• Young males at greater risk than young females
• Estrogen protective

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• 3. Genetics/Family history
• Unclear how much is genetics how much is
  learned behaviours
• New research in genetic typing gene specific
  treatment emerging
• Unclear if this will benefit the general
  population

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• 4. Ethnicity
• Canadians not born in Canada have different CVD
  rates than native-born Canadians
• Unclear if this is genetic, behavioural or
  environmental (or a combination of all 3)

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• Modifiable
• 1. Smoking
• Multiple mechanisms increase risk for CVD
• Decreases high density lipo-proteins (HDL)
• Increases platelet aggregation fibrigonen
  levels
• Increases vasospasm
• Increases anti-estrogenic effects early
  menopause

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• Smoking a particular risk for females using oral
  contraceptives

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• 2. Diet
• Consumption of 5 10 servings of fresh fruit
  vegetables protective
• Low fat intake and avoidance of saturated fats
  protective
• More than 5-7 cups caffeinated beverages
  increases risk

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• 3. Activity levels
• Reduce body weight
• Improve serum lipid levels
• Reduce blood pressure
• Reduce risk for diabetes hypertension

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• 4. Overweight/obesity
• Overweight defined as Body Mass Index (BMI) of 25
  -29.9
• Obesity BMI gt 30.0
• Increases risk for hypertension diabetes
• Risk increases with body weight

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• 5. Alcohol consumption
• More than 2 drinks/day associated with
• CVD
• Hypertension
• 1 drink/day is protective
• Abstainers have a higher risk than those who
  consume 1 drink/day

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• 5. Stress
• Cardiac effects
• Increased oxygen demand
• Platelet aggregation
• Vasoconstriction
• Mediated by
• Coping skills
• Support system

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• 6. Exertion in the cold
• Snow shovelling
• ½ of cold related deaths attributed to
• MI
• CVA
• Most occur in people with underlying disease

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• 7. Social risk factors
• Social isolation
• Poverty
• Low educational attainment
• Blue collar employment
• 6 or more years of shift work

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Primary Prevention

• Behavioural Interventions
• 1. Smoking cessation
• 2. Dietary Intake
• 3. Increase physical activity

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• 4. Maintain optimal body weight
• 5. Low to moderate alcohol consumption
• 6. Reduce stress
• 7. Minimize exertion in cold weather

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• But is it really that simple?
• And what about those social risk factors?

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Secondary Prevention

• Screening
• Hypertension
• Dyslipidemia
• Obesity
• Dietary patterns
• Smoking

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Prevention of Type 2 Diabetes
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• Major source for this section
• Health Canada web-site
• Canadian Diabetes Association web-site

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Definition

• Type 2 diabetes (non-insulin dependent diabetes
  mellitus NIDDM) is a metabolic disease in which
  carbohydrate use is reduced that of lipid and
  protein is enhanced
• Caused by 2 processes
• Resistance to insulin action
• Failure of pancreas to increase insulin
  production

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Epidemiology

• 90 of all diabetes diagnosed in Canada is type 2
  diabetes
• 7th leading cause of death in Canada
• The disease and its complications account for
  25,000 PYLL before age 75
• 40 of those with diabetes develop long-term
  complications

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• 80 will die of CVD or CVA
• Significant risk for development of other health
  problems, e.g.
• Microvascular disease
• Visual impairment
• Renal failure
• Periodontal disease

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• Associated direct health care costs amount to 9
  billion/yr.
• Indirect health care costs also significant
• Significant impact on quality of life

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• 2.25 million Canadians have diabetes
• 1/3 are unaware they have the disease
• Incidence and prevalence of diabetes is rising

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• Three particularly disturbing trends
• Increased incidence in aboriginal populations
• Increased incidence in children adolescents
• Increased incidence other ethnic groups
• Hispanic
• Asian
• South Asian
• African

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Risk Factors for Type 2 Diabetes

• Type 2 diabetes is also considered to be largely
  preventable, since a great deal is known about
  the risk factors associated with it
• Diabetes is complicated by presence of other
  treatable conditions, e.g.
• hypertension

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• Non-Modifiable
• 1. Age
• Risk rises with age
• Prevalence 3X higher in those aged 65 than in
  those aged 35-64

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• 2. Genetics/Race/Ethnicity
• Difficult to disentangle impact of
• Socioeconomic status
• Dietary pattern
• Genetics

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• Modifiable
• 1. Smoking
• May be an independent risk factor for diabetes
• Epidemiological data suggests higher risk of
  diabetes in those who smoke
• Smoking also exacerbates complications of diabetes

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• 2. Diet
• Maintenance of energy balance
• Limitation of saturated fat intake
• Higher dietary fibre intake may also reduce risk

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• 3. Activity Levels
• 4. Overweight/Obesity

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Primary Prevention

• Behavioural Interventions
• 1. Smoking cessation
• 2. Dietary Intake
• 3. Increase physical activity

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• 4. Maintain optimal body weight
• But is it really that simple?
• And how is it that poverty is sometimes listed as
  a risk factor?

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• Class exercise
• In the following table, place a tick mark beside
  each risk factor known to increase risk for the
  disease listed at the top of each column
• Which three risk factors would you choose to
  focus on if you were asked to reduce the
  incidence of these 3 diseases?

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