5907415 epidemiology of noncommunicable diseases
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Epidemiology of Non-
Communicable Diseases
Adora F. Mendoza-Abat, M.D., CFP
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Definitions
Environmental Epidemiology the studyof environmental factors that influence thedistribution of diseases in the human
population
Occupational Epidemiology the study of
workplace exposures on the frequencyand distribution of diseases and injuries inthe population
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Infectious Diseases Non-Infectious Diseases
-Single necessary agent
-Specific agent-diseaserelationship
-Causes are relatively wellunderstood
-Short incubation period
-No single necessary agent
- One-to-onecorrespondence betweenagent and disease very rare
-Causes unknown,intervention usually based
on risk factors
-Long latency period
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Infectious Diseases Non-Infectious Diseases
-Single exposure usuallysufficient
-Usually produce acute
disease
-Acquired immunity possible
-Dx based on tests specificto disease agent
-May require multipleexposure to same ormultiple agents
-Most often produce
chronic disease
-Acquired immune unlikely
-Dx often dependent onnonspecific symptoms ortest
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Classification of Etiologic Agents orRisk Factors
1. Environmental Factors that may AffectHealth
A. Psychological Factors
B. Biological Factors
C. Chemical Factors
D. Physical Factors E. Accidental Factors
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Classificatn of Etiologic Agents or RiskFactors
2. Environmental Components & Health Hazards
Components Health Hazards
Physical : air, water, soil,
food, climate and weather,noise level, radiation level
Social: work, transport,
leisure, housing, family andcommunity
Physical: heat and cold,radiation, noise
Chemical: metals, chemicalsubstances
Biological: microorganisms,
flora and faunaSocial; culture/customs,interpersonal relations,social and politicalstructure, housing factors
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Environmental Hazards
1. Site and location (earthquakes, flood, wind,storms, drought)
2. Biological (animal, insect, microbiological,vegetation)
3. Chemical (poisons and toxins, allergens,irritants)
4. Physical (vibration, radiation, forces and
abrasion, humidity)5. Psychological (stress, boredom, anxiety,
discomfort, depression)
6. Sociological (overcrowding, isolation)
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Uses of Environmental / OccupationalEpidemiology
1. Identify etiologic factors2. Monitoring trends and changes on health
consequences/impact
3. Planning, management and evaluation ofprograms (projections and risk assessment)
4. Communicate information regarding
environmental hazards5. Basis for establishing safety standards or
thresholds
6. Others (eg. Elucidating mechanisms oftoxicity, describe dose-response relationships)
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Causes of Under-recognition ofOccupational/Environmental Dse.
1. Inherent difficulty in diagnosingoccupational diseases
2. Difficulty in establishing cause and effectrelationships
3. Lack/incomplete evaluation of chemicals forpotential toxicity
4. Inadequate pre-market evaluation of newlydeveloped chemical substances
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Causes of Under-recognition ofOccupational/Environmental Dse.
5. Long latency between occupational /environmental exposure and onset of illness
6. Lack of awareness among healthpractitioners about hazards found at work andin the environment
7. Limited ability of many workers to providean accurate report of their toxic exposures
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Causes of Under-recognition ofOccupational/Environmental Dse.
8. Resistance of employers to recognize thework relatedness of a disorder because of
possible litigations suits 9. Usually involves small group of people
10. Lack of knowledge about many aspects of
behavior of environmental pollutants 11. Potential difficulties in defining potential
risks
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Major Types of OccupationalDiseases
1. Lung diseases
2. Cancer
3. Skin disorders 4. Infectious diseases
5. Reproductive disorders
6. Musculo-skeletal disorders 7. Severe traumatic injuries
8. Hearing loss
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Surveillance Activities in Environmental/ Occupational Epidemiology
1. (Occupational) Hazard Surveillance
a. Provides a means of assessing toxic
occupational exposures to a population andthus of assessing risk
b. Will identify chemicals in use, the industries
and occupations where they are used, and theextent and magnitude of worker exposure
c. Also provides a means of identifying changesin the patterns of exposure and of noting
emerging toxic hazards
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Surveillance Activities in Environmental /Occupational Epidemiology
2. (Occupational) Disease Surveillance
a. Provides a means of assessing the amount
and types of occupational disease, time trendsand distribution according to geography,industry and occupation
b. Can consist of 2 types of surveillance
b.1. Biological monitoring
b.2. Medical Screening
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Biological Monitoring
The systematic collection of biologicalspecimens (blood, urine, breath, fingernails,hair, saliva) for the purpose of estimatingexposure to environmental agents and hence
determine the risk of disease before it occurs
Interpretation - requires detailed knowledge ofthe kinetics and metabolism of chemicals
Limitations: due to the rapid excretion ofcertain chemicals, only the most recentexposure to them are measurable; may reflect
recent exposure or cumulative exposure
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Medical Screening
The periodic examination (clinical orlaboratory) to detect diseases (or healthproblems) present among apparently
healthy subjects
Issues: validity, predictive values, cost-effectiveness, acceptability of procedure
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Measurements of Exposure andOutcome : Some Issues / Considerations
1. Exposures are usually measured quantitatively
2. Dimensions of exposure: level, duration, level-
duration combined3. Current Vs. long term exposures
a. Acute Effects current exposures are
relevant (e.g. London smog epidemic in 1952)b. Cumulative Effects
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2 Types of Cumulative Effects
1. Chemical / substances that accumulatein the body (e.g. cadmium)
2. Hazards with cumulative effects (e.g.radiation, noise)
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Measurements of Exposure and Outcome :Some Issues / Considerations
4. Individual measurements vary with timea. Has implications on the frequency, timeand method used to estimate exposure ordose
5. Exposure or dose varies between individualsa. Different work habitsb. Differences in the local distribution of
pollutantsc. Differences in individual absorption andexcretion rates for the chemical
. d. People with the same external dose mayend up with different internal doses
M t f E d
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Measurements of Exposure andOutcome : Some Issues /
Considerations 6. Internal dose (absorbed dose) is usually
different from external dose (environmental
measurements) 7. Dose-effect relationship the higher the
dose the more severe and intense is the effect;
data are useful for establishing safetystandards
Set safety standard at a level where the less
severe effects are prevented
M t f E d
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Measurements of Exposure andOutcome : Some Issues /
Considerations 8. Dose-Response Relationship
Response the proportion in an
exposed group that develops a specificeffect
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Environmental Exposures Doses are at concentrations far below those
experienced by workers who are directlyhandling the materials
Will require larger population for study in order
to detect the smaller health effects likely toresult
Problems with confounding variables may be
more serious Estimation of exposure doses is complicated by
the lack of routine data on air and water
pollution
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Environmental Exposures
Use of place of residence as surrogate for
exposure may lead to exposuremisclassification because population may behighly mobile
Common to use ecologic data or correlationalstudies
Longer exposure of residents to household
toxin compared to workers Children are more susceptible than working
adults since they have faster metabolism and
absorption of the toxin
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Risk Assessment
The use of epidemiological methods andprinciples to estimate the potential healthrisks of industrial or agricultural
development projects, both before theyare implemented and while they are inoperation.
Used to predict potential health problemsin the use of new chemicals ortechnologies
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Steps in Risk Assessment
1. Identify which environmental hazard may becreated by the technology or project understudy (Hazard Identification)
2. Analyze the type of health effect that each
hazard may cause (Hazard Assessment)3. Measure or estimate the actual exposure
levels for the people potentially affected,including the general population and the workforce (Measure Actual Exposure)
- Use data on environmental and biologicmonitoring, relevant hx of exposure and
changes over time
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Steps in Risk Assessment
4. Calculate the likely health risk in thepopulation
- For each hazard identified, the exposuredata for subgroups of the exposedpopulation are combined with the dose-effect and dose-response relationships
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BURDEN OF NCDs
rising trends in non-communicable diseases as aresult of demographic and epidemiologicalchanges, as well as economic globalization
increase in life expectancy combined with changesin lifestyles are leading to epidemics of non-communicable diseases (NCD), mainlycardiovascular diseases, cancer and diabetes
In 1998, NCD accounts for 63% of global deaths
43% of all DALY globally were attributed to NCD
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Non-Communicable Diseases
Includes all traditionally defined NCDssuch as CVD, cancer, chronic respiratorydiseases, mental health as well as injuries
and violence
In all WHO regions (except sub-SaharanAfrica), NCDs today constitute the largest
contributor to burden
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NCDs accounted for 60% of all deaths in1999 and 43% of all DALYs with injuriesadding 9% of all deaths and 14% of all
DALYs
By 2020, 10 out the top 15 causes ofDALYs lost will be attributable to NCDs,
mental health and injuries/violence
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The top five positions will be occupied byIschemic Heart Disease, depression, roadtraffic injuries, cerebrovascular disease
and Chronic Obstructive PulmonaryDisease (COPD)
15th place: trachea, bronchus and lung
cancers (better known as tobacco cancers)
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GROUP OF NCDs
Cancers Lifestyle-related (CVD, diabetes)
Injury (unintentional, intentional)
Genetic disorders
Disabling disorders
Occupational disorders
Nutritional conditions
Endocrine disorders Substance abuse
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REASONS FOR THEPROMINENCE OF NCD
1. Aging of the population
2. Impact of automobiles
3. Lifestyle changes
4. Tobacco addiction
-single largest cause of preventable morbidity
and mortality
5. Physical activity6. Social and behavioral factors
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A. CHARACTERISTICS OF THE AGENTe
Absence of a single necessary agent
most NCDs are classified on the basis ofmanifestations rather than on etiology (e.g.,CVD, renal disease, neoplasms)
known causes are risk factors
e.g. obesity, elevated cholesterol levels,hypertension
I. NATURAL HISTORY
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B. TIME FRAME
- take years or decades before illness is
apparent
- no multiplication of causative agent isinvolved
- multiple low-dose exposures (somechemicals)
- some conditions seem to evolvesubsequent to chronic conditions orhigh risk states such as obesity,smoking, diabetes and high bloodcholesterol
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C. NATURE OF THE DISEASE
chronic in nature
chronic disease
(1957 Commission on Chronic Disease)
permanent
leaves residual disability
caused by nonreversible pathologicalalterations
requires special training of the patientfor rehabilitation
requires long periods of supervision,observation or care.
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Chronicity
function of the long latency period
slow disease process adaptiveresponses to stresses (may bedetrimental over the long term)
CD can be chronic (e.g. rheumaticheart disease)
NCD can be acute (e.g. chemicalpoisoning)
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D. Synergism in Disease Causation
> Asbestos and lung cancer (RR=8)> Smoking + asbestos and lung
cancer (RR=90)
- Presence of synergism decreasedlatency (produce illness in the prime oflife even with low level exposures)
- Role of initiators and promoters
M j C i f
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Major Categories ofEtiological Agents
A. Occupational
B. General environmental
C. Lifestyle and Illness
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OCCUPATIONAL
- chemical
- metals and naturally occurring minerals
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Investigating occupational exposures
agent factors to be considered
size and shape of particles
route of exposure
free or compound form
organic vs inorganic form
liquid or vapor form
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environmental factorsconditions in the work environmental
that will influence the likelihood thatworkers will come in contact with anagent
general cleanliness and ventilation
lighting, temperature
Host factors lifestyle behaviors that may increase
the risk of disease from occupationalexposure to an agent
genetic constitution
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ENVIRONMENTAL
sources of exposure contamination of air, water and soil by
industrial activities or inadequate wastedisposal
lower dose of exposure than inoccupational environments
pesticides
housing materialsautomobile exhausts
radiation
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Investigating environmental exposures
dose
data on levels of exposuremobility of subjects
confounders
additional considerations
wide range of ages
length of exposure
meterological conditions
seasonal effects
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LIFESTYLE
- poverty, stress, exercise, drug and alcohol
use, nutrition
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CONTROL OF NCD
A. PRIMARY PREVENTION- removal of agent from environmental orminimizing the amount of agent present
- Protection of the susceptible host from
exposure
B. SECONDARY PREVENTION
- screening tests
C. TERTIARY PREVENTION
- lifestyle modification
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A small core of risk factors explains the increases inCVD, certain cancers and their closely linkedconditions of obesity, type II diabetes:
tobacco, diet/nutrition, physical inactivity andalcohol
A substantial proportion of chronic respiratorydiseases and death are driven by tobacco use
Alcohol is obviously a major contributor to all causesof injuries and violence
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Tobacco trends are not hopeful
There are 1.2 billion smokers in the worldwith smoking rates in 13 to 15 year oldsbeing about 20% in diverse cities fromdeveloped and developing countries
Tobacco causes 4 million deaths per year,a figure that will increase to 10 million per
year by the late 2020s The public health impact is widespread and
increasing fast in developing countries
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Trends in alcohol use:
steady increases in many developingcountries with continued very high rates of
binge drinking in many east and centralEuropean countries.
Alcohol Use
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Obesity
has tripled in youth in several Chinese cities,
and rapidly increased over the last 15 years inthe major cities of countries like Malaysia,Brazil, Indonesia and South Africa
But these have occurred as underweightpersists in the rural areas
Often underweight is common in the sameneighborhoods as obesity is increasing
Thus both being underweight and beingoverweight are associated with poverty
Ob it ( t)
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Epidemics of obesity and type II diabetes
have been well documented in mostPacific Island States and are probablyfuelled by a combination of factors:
increased imports of high fat foodsparticularly cheap off-cuts as well asincreased consumption of sodas in societieswhere physical activity levels haveplummeted.
Devastating economic impact of diabetescomplications are recently beingdetermined for several of these countries
Obesity (cont)
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The problems of obesity and diabetesare caused by many factors
Solutions similarly need to bemultidimensional and avoid focusing on
just one aspect or on behavior change
alone
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Mental health:
450 million people who suffer frommental or neurological disorders orfrom psychosocial problems such asthose related to alcohol and drug abuse
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