Deterninants Prognostic factors
Causal factors Risk factors
Epidemiology is the study of
2. Performance of the
Epidemiology: Is a term derived from the Greek language (epi = upon, demos = people,
logos = science). [Epidemiology is] the study of the occurrence and distribution of
health-related states or events in specified populations, including the study of the
determinants influencing such states, and the application of this knowledge to control the
Applications of epidemiology in public health:
1. Community health assessment and priority setting
2. Evaluating health interventions and programs
3. Preventing disease and promoting health
4. Improving diagnosis, treatment and prognosis of clinical disease
Basic Epidemiological information about a disease:
1. Natural history in the individual:
odevelopment with age (cohort basis)
oearly indicators (for screening)
oimpact of different treatments
opossibility of cure
oneed for care
ospecific causal factors
oother risk factors
3. Development in the community:
ovariations with age (cross-sectional basis)
4. Differences in occurrence:
5. Possibilities for prevention:
ospecific actions to address causal factors and underlying
ogeneral actions to address other risk factors
oimpact of medical services including screening and early
o impact of health policy
1.Natural History and Prognosis
Natural history: refers to the stages of a disease, which include:
• Pathological onset
• The preclinical phase: from the onset of pathological changes to the first appearance of
symptoms or signs; and
• The clinical phase: The stage when the disease is clinically obvious and may be
subject to remission, relapse or progress to death.
Detection and treatment at any stage can alter the natural history of a disease, but the effects
of treatment can only be determined if the natural history of the disease in the absence of
treatment is known.
Prognosis: is the prediction of the course of a disease and is expressed as the probability that
a particular event will occur in the future. Knowledge of the prognosis is helpful in
determining the most useful treatment.
Prognostic factors are characteristics associated with outcome in patients with the disease in
question. For example, in a patient with acute myocardial infarction, the prognosis is directly
related to residual heart muscle function.
2.Disease Etiology (Causation)
Aetiology: The science or philosophy of causation.
There are two models widely applied to know the causation of a disease:
a) The Epidemiological Triad. Is
used to describe the intersection of Host,
Agent, and Environment in analyzing an
b) The sufficient cause and component causes model
• A sufficient cause is a set of factors or conditions that produces disease.
• The factors or conditions that form a sufficient cause are called component causes.
Component causes include host factors, agents and environmental factors.
• If a disease does not develop without the presence of a particular component cause,
then that component cause is classified as a necessary cause. However, a single
component cause, even if it is a necessary cause, is rarely a sufficient cause by itself.
• Causal Factors:
Four types of factors play a part in the causation of disease, all may be necessary but they
are rarely sufficient to cause a particular disease or state:
1. Predisposing factors, such as age, sex, or specific genetic traits that may result in a
poorly functioning immune system or slow metabolism of a toxic chemical. Previous
illness may also create a state of susceptibility to a disease agent.
2. Enabling (or disabling) factors: such as low income, poor nutrition, bad housing and
inadequate medical care may lead to the development of disease. Conversely,
circumstances that assist in recovery from illness or in the maintenance of good health
could also be called enabling factors. The social and economic determinants of health
are just as important as the precipitating factors in designing prevention approaches.
3. Precipitating factors such as exposure to a specific disease agent may be associated
with the onset of a disease.
4. Reinforcing factors such as repeated exposure, environmental conditions and unduly
hard work may aggravate an established disease or injury.
• Risk factor: Patient characteristic (either inherited, such as a blood group, or
behavioral, such as smoking and diet habits) or environmental factor (such as exposure
to asbestos) associated with an increased or decreased probability (risk) of developing a
disease (or other outcome). They are any factor that are associated with the risk of
development of a disease but that are not sufficient to cause the disease
• Health and disease determinants:
Determinant: is any factor, whether an event, characteristic, or other definable entity, that
contributes to a change in health. It is common to refer to proximal and distal
4- Epidemiological Measures of Health and
a)Measures of disease Frequency.
1. Incidence rate (IR): how fast new occurrences of disease arise?
A: The number of existing affected individuals, or cases
PT: person-time = size of entire population × length of observation
2. Prevalence (P): the amount of disease already present in a population
C: The number of existing affected individuals, or cases
N: number of persons in the population
3. Risk (R): an individual will contract a disease. Also called (Cumulative incidence)
b)Measures of exposure effect and impact.
a. Risk ratio= Risk (cumulative incidence) in the exposed group
Risk (cumulative incidence) in the unexposed group
b. Rate ratio = Incidence rate in the exposed group
Incidence rate in the unexposed group
c. Odds ratio = Odds of disease in the exposed group
Odds of disease in the unexposed group
Odds of disease = Probability of getting the disease by the end of time period
Probability of not getting the disease by the end of the time period
a. Attributable risk = Incidence in exposed group − Incidence in non-exposed group.
b. Attributable risk percent = Incidence in exposed gp − Incidence in non-exposed gp
Incidence in exposed group
c. Attributable fraction = Risk (or rate) ratio - 1
Risk (or rate) ratio
d. Population attributable risk fraction=
Incidence in the whole population - Incidence in the non-exposed population
Incidence in the whole population
e. Population attributable risk=
The proportion of the population in the exposed group (p) × Attributable risk.
f. Population attributable fraction = Population attributable risk
Risk of disease in population
1.Mortality, Morbidity and Disability Rates
2.Fatality and Life Expectancy Rates
4- Disease Classification
International Classification of Diseases (ICD): It is used to classify diseases and
other health problems recorded on many types of health and vital records.
The broad categories, used by the World Health Organization and the World Bank in the
Global Burden of Disease Study, are:
1- Communicable, maternal, prenatal and nutritional conditions: including all
infectious diseases, deaths in women related to pregnancy, prenatal deaths, which
include still births and deaths within the first week of life, and nutritional conditions
such as protein-energy malnutrition and vitamin A deficiency.
2- Non-communicable diseases: covering cardiovascular diseases, cancers, endocrine
conditions, such as diabetes, and neuropsychiatric disorders, which includes alcohol
and drug use disorders.
3- Injuries, which include unintentional injuries, such as road traffic accidents, and
intentional injuries, such as suicide and violence against others.
• The aim of screening is to identify asymptomatic disease, or risk factors for
disease, by testing a population that has not yet developed clinical symptoms.
• Screening tests are often not diagnostic and usually seek to identify small
numbers of individuals at high risk of a particular condition. Further tests are
needed to confirm a diagnosis.
• a screening test can identify individuals with a disease before the presence of
disease is detected by routine diagnosis (eg, when symptoms occur),
• Treatment at the time of detection by screening, as opposed to the time of routine
diagnosis, results in an improved chance of survival.
• A screening program can either include the whole population (mass screening) or
selected groups who are anticipated to have an increased prevalence of the condition
for which screening has been instituted (targeted screening)..
Evaluation of screening tests:
1. Reliability: a test measures a variable consistently and is free of random error.
2. Feasibility: A screening test should be inexpensive, easy to administer and
impose minimal discomfort on those to whom it is administered.
3. Validity (accuracy): a test is able to differentiate between individuals with a
disease, or its precursor, and those without.
Measures of validity:
1. Sensitivity: probability to test positive among truly affected
2. Specificity: probability to test negative among truly unaffected
3. Positive Predictive (PV+
) and Negative Predictive values (PV-
4. Prevalence = a + d .
a + b + c + d
5. Efficiency % = a + c . ×100
a + b + c + d
6. Risk ratio = a/(a + b)
c/(c + d)
7. Odds ratio = ad
8. ROC curves: receiver operating characteristic (ROC) curve. These curves plot test
sensitivity on the Y-axis vs. 1 − specificity on the X-axis. Figure 12.3 presents an ROC
curve for the PSA test.
The solid line on the ROC curve represents the performance of the PSA test, and the
dashed, diagonal line represents the performance of a hypothetical test that is
completely uninformative. A perfect test would start at the lower left-hand corner of
the graph, rapidly increase in near vertical fashion toward perfect sensitivity, and then
move horizontally across the graph to the upper right-hand corner. Every continuous
test will have its own a unique ROC curve.
6- Levels of Prevention
1. Primary prevention: responsible for keeping people healthy and preventing them
from getting ill, through:
a) Health promotion: it means the achievement and maintenance of optimum
level of health, through:
• Sanitary environment.
• Health education.
• Nutritional supplementation.
• Social development.
b) Health education: to change unsound healthy behavior method through:
personal approach, mass media, and community participation.
c) Specific prevention:
• Immunization (passive and active).
• Nutritional supplementation (prevention of certain deficiencies)
• Others: as prophylactic diet, clothes.....
2. Secondary prevention: it is concerned with detection of the disease with prompt
and proper treatment.
a) Early detection:
• Periodic examination specifically of vulnerable groups as mothers and the
• Periodic examination of the high risk groups, e.g. screening for cancer.
b) Prompt and appropriate treatment: aims at achieving complete cure and
3. Tertiary prevention: concerned with limitation and rehabilitation of handicapped.
a) Limitation of disability: by early medical interference.
b) Rehabilitation: physical, social, and psychological rehabilitation.
7- Epidemiological Study Designs
Epidemiological studies can be classified as either observational or experimental.
a. Observational studies allow nature to take its course: the investigator measures but
does not intervene. They include studies that can be called descriptive or analytical.
1. Descriptive studies: is limited to a description of the distribution and frequency of
diseases, and possible causes of diseases in populations. It is often the first step in
an epidemiological investigation.
Ecological studies: the units of analysis are populations or groups of people rather
2. Analytical studies: goes further by analyzing relationships between health status
and other variables (such as smoking, diet or socio-economic status)
Types of study which are used for this are cohort studies, case-control studies or
b. Experimental studies (Interventions):
Randomized controlled trials using patients as subjects (clinical trials),
Field trials in which the participants are healthy people.
Community trials in which the participants are the communities themselves.
Stratification of Disease Frequency by Person, Place, and Time
Once we calculate measures of disease frequency,
we can examine whether these measures vary by
personal characteristics, geography, and/or time
Stratification refers to the process of separating
analysis by subgroups.
For example, the prevalence of diabetes among all
US adults is approximately 9.0%; the prevalence of
diabetes stratified by race is 8.2% among whites and
14.9% among Native Americans.
a. Disease Frequency Measurements Stratified by Characteristics of Person
Examples of personal characteristics include age, race/ethnicity, and sex.
For example, polycythemia vera is a myeloproliferative disorder characterized by an
abnormal increase in red blood cell mass. The estimated prevalence of polycythemia vera
among individuals aged 35–44 is 9 cases per 100,000, whereas the estimated prevalence in
people aged 75–84 is 163 cases per 100,000. Polycythemia rates are also greater in men
and in people of Jewish/Eastern European ancestry.
These data begin to define risk factors for the disease.
b. Disease Frequency Measurements Stratified by Characteristics of Place
The incidence of a disease varies by geographic region.
For example, the incidence of multiple sclerosis varies by geographic region within the
USA. Areas with the lowest sunlight exposure, such as Seattle, have the highest incidence
of multiple sclerosis.
Vitamin D is ascertained from sunlight exposure and may play an important role in
suppressing autoimmunity. Circulating vitamin D levels are particularly low in regions
with reduced sunlight exposure.
These disease frequency data, stratified by place, suggest the hypothesis that vitamin D
deficiency may play a role in the pathogenesis of multiple sclerosis.
c. Disease Frequency Measurements Stratified by Characteristics of Time
In 1970, approximately 5% of all births in the USA were by Cesarean section delivery. By
the year 2000, nearly 25% of US babies were born by Cesarean section. These strong
temporal changes in rates generate a number of hypotheses.
One possibility is that maternal age has also increased during this time period, leading to
more complicated pregnancies that may require Cesarean section.
A second possibility is that improved fetal monitoring technology that can detect small
changes in fetal status may prompt more surgical intervention.
A third possibility is that the routine use of repeat Cesarean section has become standard
practice in the USA because of data demonstrating an increased risk of uterine rupture in
women who have a vaginal birth after a first Cesarean section.
Disease frequency measurements stratified by time are often hypothesis generating,
motivating further studies to uncover the true causes of a disease process.
Types of analytical studies:
1. Case-control studies, comparing people who develop a condition with people who
2. Cohort studies, Follow-up (retrospective, prospective) studies.
People without the disease are followed up to see who develops it, and disease incidence
in persons with a characteristic is compared with incidence in persons without the
Follow-up studies may be done "retrospectively"(or historical), where the population at
risk can be defined at some time in the past and traced forward in time, or
"prospectively" (or concurrent), where the population is identified or assembled by the
investigator and then followed forward in time.
3. Cross-Sectional (prevalence) surveys: A cross-sectional study refers to a study design
which measures the exposure and outcome at the same time; this means that there is no
follow up time in a cross-sectional study.
1. Measures the exposure and the outcome at the same time.
2. Estimate the prevalence of a disease or condition.
3. Cannot establish a temporal relationship between the exposure and the outcome.
In a case–control study, a group of cases (individuals who have the disease or outcome
of interest) and a group of controls (individuals who do not have the disease or
outcome of interest) are identified.
The prevalence or level of exposure to a risk (or protective) factor is measured and
compared between the two groups. Usually, this study design is less time-consuming
and less expensive.
The design allows the investigation of several risk factors for a given disease at the
same time, and the study of rare diseases.
It is possible to calculate the odds of exposure among cases and among controls and
obtain an odds ratio of exposure
In case–control studies, participants are selected on the basis of their disease status and
not their exposure status. Therefore, it is not possible to calculate the incidence of
disease in the exposed and unexposed individuals.
In a cohort study, participants are followed over time to see whether they develop the
disease of interest.
Participants are selected on the basis of whether they are exposed to a potential risk
factor. All participants should be free of the disease under investigation at the start of
In a prospective cohort study the investigator assembles the study groups on the basis
of exposure to a risk factor, collects baseline data, and continues to collect data on the
outcome and other relevant variables over time.
Exposure Study starts
Prospective cohort study
In a retrospective cohort study, the investigator goes back in time to define the
exposed and unexposed groups and reviews medical records to follow participants and
review outcomes to the present day.
Retrospective cohort studies
occurrence Study starts
Cohort studies can be used to measure:
1. All three measures of relative risk (risk ratio, rate ratio, and odds ratio) .
2. The incidence of disease in the exposed and unexposed groups.
3. Standardized mortality ratios.
4. Attributable risk and population attributable risk.
3.Experimental Studies (intervention studies)
There are two main types of intervention study, therapeutic studies and preventive
Therapeutic studies are designed to test the effect of therapies, which could be new
drugs, surgery or vaccines, in people who already have a particular disease. These
studies are also referred to as clinical trials.
Preventive studies designed to evaluate prevention strategies, on the other hand, are
carried out on people who do not have a disease but are considered ‘at risk’. These
studies are also referred to as field trials, and may take the form of a trial to test
health education methods, training procedures or other public health programs.
An intervention study is an epidemiological experiment in which the investigator
randomly allocates selected individuals (or groups of individuals) to an
intervention group (the group that receives the intervention under investigation)
or to control group (the group that does not receive the intervention). The
investigator then measures and compares the incidence of the outcome of interest
in the two groups. An example of a group-level study is a field trial or a cluster
randomized trial, and an example of an individual study is a randomized
The main measures of effect obtained from an intervention study are the risk ratio
or rate ratio. It is also possible to calculate the attributable risk and the population
attributable risk from the results of an intervention study.
Studies to test new drugs or surgical procedures are conducted in four phases..
Phases of Drug Development,
Phase I and II studies are typically not randomized trials but are used to develop
randomized phase III and IV studies.
Phase I Studies
Phase I studies introduce a new drug to humans (usually healthy volunteers) to
determine how a drug should be administered (e.g. by mouth, injection into the
blood, or injection into the muscle). They also review side effects, safety and the
dosage of the drug, and are usually only carried out on a small numbers of people.
Phase I studies cannot be performed in healthy adults because the drug has
unacceptable adverse effects, such as a chemotherapeutic agent.
Phase II Studies
Phase II studies evaluate efficacy and safety in selected populations of about 100–
300 patients who have the disease or condition to be treated, diagnosed, or
Participants tend to be hospitalized patients who can be closely monitored. The focus
is on dose–response relationships, type of patient, frequency of dosing, or any of a
number of other issues involved in safety and efficacy.
Phase IIa studies are clinical trials and Phase IIb studies are controlled trials.
Phase II data are used to inform phase III studies.
Phase III/IV Studies
Phase III studies are randomized trials designed to assess the effectiveness and safety
of an intervention.
Outcomes of phase III studies are typically clinical events, such as death or tumor-
Safety assessments occur over a longer period compared with phase II studies.
Phase IIIb studies are randomized trials that occur after a drug has been submitted
for approval, but before approval has been granted.
Phase IV studies occur after approval.
Phase IV studies evaluate outcomes associated with a drug or intervention as it is
used in clinical practice.
Both phase IIIb and phase IV studies typically focus on long-term safety
8- Epidemiology of Communicable Diseases
1. Natural History of Communicable Diseases:
Chain of Infection
Each case of communicable disease is the result of an orderly progression in a series
of events, this series of events may be described as a three-link chain
"(epidemiological triad), each link representing a factor essential to the transmission
of disease. These links are:
1. The source of the disease agent (reservoir)
2. The means by which the disease may be transmitted (mode of transmission).
3. A susceptible person (host).
a. Patterns and extent of infections:
Sporadic: scattered cases which are separated from each other. There is unknown
common source of infection.
Endemic: refers to the fact that a particular disease is usually found in a particular
area all over the year. For example, malaria is endemic in the southern hemisphere.
Epidemic: a relatively sudden increase in the number of cases of a particular
disease in a particular place or area, the area and the number of increased cases are
always part of the description of any epidemic.
Pandemic: an epidemic that encompasses a wide geographical area (many
countries). In the past pandemics were rare, but through the combination of
worldwide rapid travel and the burgeoning human population (~6billion),
pandemics are likely to be increasingly in our future.
b. Mode of Transmission:
1. Air borne (Droplet) infection:
• These are usually transmitted from person to person by discharges (spray, cough,
sneeze, breath) from the nose, mouth, throat, or lungs of an infected individual.
• Examples: common cold, pneumonia, sore throat, and tuberculosis.
2. Food borne infection:
These are usually transmitted by food and water that has become contaminated with
feces or urine from an infected human or animal.
• Examples: typhoid, and paratyphoid fevers, dysentery, and cholera.
3. Contact infection:
• Transmitted by contact of the skin or mucus membranes with the pathogenic
1. Direct contact to intact skin: Examples: scabies, and anthrax
2. Venereal (sexual transmitted) infection: Examples: syphilis, gonorrhea, and
3. Contact to damaged skin:
i. Wound infection: Examples: Tetanus and gas gangrene
ii. Blood borne infection: Examples: viral hepatitis, and AIDS
iii. Animal bite (part of Animal borne infection): Example: rabies
4. Arthropod borne infection:
•Transmitted from person" to person (or from animal to person) by arthropods.
• Examples: malaria, typhus, and yellow fever.
N.B. Animal borne infection (Zoonoses):
• They are diseases naturally transmitted from animals to man.
1. Air borne infection: e.g. Q fever, anthrax, tuberculosis
2. Food borne infection: e.g. typhoid, brucellosis, anthrax, tuberculosis
3. Contact infection: e.g. anthrax, rabies, brucellosis
4. Arthropod borne infection
c. General measures towards control of infectious (communicable)
Breaking anyone of the links in the chain will prevent the spread of the disease.
1. Control of the disease source:
One means of breaking the chain of disease transmission is through measures for
controlling sick individuals (cases), carriers, and animal reservoirs. These control
a. Isolation: isolation is a procedure whereby infected persons (cases or carriers) are
separated from other individuals. Usually this separation is accomplished by having
the patient admitted to the isolation ward in the hospital. Clothing and linens used by
infected individuals are laundered with soap and hot water. Other contaminated
articles are washed scrubbed aired, sunned, or incinerated as appropriate to the article.
Mattresses and pillows used by apparently well persons should be sunned at intervals
to destroy and bacteria that may be on them.
b. Quarantine: quarantine is the restriction of freedom of movement of those
individuals who may have been in contact with a case and who may themselves
develop and further spread the disease. In this case, the individual is only suspected of
having a contagious disease; however, if an individual is known to have a disease of a
communicable nature, he may likely be placed in isolation rather than in quarantine.
c. Medical Surveillance: this measure may be carried out in two ways:
• When cases or suspected cases of certain communicable diseases occur, all persons
who are their contacts may be inspected daily during the incubation (developmental)
period of the disease in order to detect new cases of the disease that may be
• In the presence of a threatened epidemic, examinations of all troops may be ordered
at stated intervals for the purpose of detecting early cases.
d. Treatment: when discovered, all cases of disease are treated. In this way, the
disease agents are destroyed and will not spread further.
e. Personal Hygiene: the spread of disease agents from infected individuals can be
prevented or greatly reduced by careful observance of the rules of personal hygiene by
strictly adhering to healthful habits and practices.
f. Animal Reservoirs: control of animal reservoirs which tend to live in close
proximity to man will do much to reduce the communicable disease hazard. Rats are
reservoirs for a number of diseases, including plague, enteric salmonellosis, rat bite
fever, and trichinosis. They may transmit these diseases to humans through fleas, by
contaminating food or water, or by other means. Mice also are health hazards. Rats
and mice should be exterminated; the usual method is by poisoning. In addition,
denying rodents access to food, water, and shelter will prevent new colonies from
being established in the area. Quarantine and immunization of domestic animals may
sometimes be required to help prevent the spread of other diseases, such as rabies and
tuberculosis. Household pets, especially dogs, may be sources of disease.
2. Control of vehicle or transmitting agent:
To prevent the transmission of disease organisms, the following measures of
environmental sanitation should be practiced as rigidly as possible:
a. Avoidance of overcrowding and close physical contact.
b. Proper ventilation of living quarters.
c. Water purification.
d. Careful selection and preparation of food.
e. Maintenance of food service sanitation.
f. Sanitary waste disposal.
g. Proper control of disease-bearing arthropods and animals.
h. Encouragement of the individual practice of personal hygiene.
3. Protection of the susceptible persons
In general, susceptibles should be protected by all measures which improve general
health. It is a well-known fact that the individual who has good mental and physical
health has good resistance to disease. Other protective measures include:
a. Personal hygiene: the practice of personal hygiene will assist in preventing disease
agents from entering the body.
b. Immunization: while immunization is an excellent method of control for some
diseases, it cannot be relied on completely. It should be used in conjunction with other
control measures. Immunizations are rarely 100 percent effective in preventing a
c. Prophylaxis: prophylaxis refers to a direct measure used to prevent or help prevent
a disease. For example diseases, including malaria, may be prevented or suppressed
by medication given before exposure to the disease, but such prophylaxis should be
used only upon orders of competent medical authority.
d. Adequate nutrition: an improperly nourished body is especially susceptible to the
invasion of disease germs. To remain "healthy," an individual should eat adequate
e. Adequate Rest. Insufficient rest prevents the body from rebuilding cells that have
been used to provide energy for mental and physical activities.
9- Epidemiology of Chronic Diseases
What is Chronic Disease?
Chronic disease can be defined as impairments or deviations from the normal status of an
individual which have one or more of the following characteristics:
Leave residual disability
Caused by non-reversible pathological alterations
Require special training of the patient for rehabilitation
Require a long term supervision
Examples: Diabetes Mellitus, Cancer, Hypertension, Asthma, etc.
What is Risk Factor?
Risk factor can be defined as an aspect of personal behavior or lifestyle, environmental
exposure, or inborn or inherited characteristic, which is known to be associated with a
health-related condition considered important to prevent
Risk Factors for Chronic Diseases
Life style changes (dietary patterns, physical activity)
Personality (type A)
Control of Chronic Diseases
Major Non-communicable Diseases (NCDs):
Chronic respiratory diseases
Clean indoor air laws in public places
Comprehensive bans on advertising of tobacco products
Information dissemination through health warning labels, counter-advertising, and
Nicotine replacement therapy (NRT)
An action taken to prevent the development of a certain diseases in a person who is
well and does not have the disease yet, e.g. immunization against hepatitis B virus
(HBV) and human papilloma virus (HPV)
Depends on identifying and attacking risk factors, such as smoking, hypertension, and
Increase avoidance of the risk factors.
Once the disease has occurred, we can identify it at an earlier stage in the natural
Secondary prevention depends on screening and early detection, and is of value in
certain conditions, such as breast and cervical cancer.
The aim is to detect the disease at early stages and before complications arise.
There are two components of early detection efforts:
1. Education to help people recognize early signs of disease and seek prompt medical
attention with early symptoms of a disease.
2. Screening programs to identify early disease before signs are recognizable such as
mammography for breast cancer, and cytology (pap smear) for cervical cancer.
About 40% of the cancer burden could be decreased if cases were detected and
Medical care is largely involved with tertiary prevention of these conditions
Aims to prolong life and improve quality of life for patients.
To provide palliative care for patients and their families in low resource settings
Improve access to good quality healthcare focusing on cost-effective and equitable
interventions for people with chronic diseases.