Measuring the health of populations is fundamental to improving their health status.
Traditionally, public health deals with the health of populations, while the New Public Health deals with the health of both individuals and population groups.
The public health professional working with individual and community health needs to acquire the knowledge and skills necessary to measure and interpret the factors that relate to disease and health, both in the individual and in population groups.
Demography and epidemiology are the basis of health information systems, but the social and basic medical sciences are also vitally important in understanding public health, providing an expanding array of health status indicators and measures of the impact of interventions.
Demography
Demography is "the study of populations, especially with reference to size and density, fertility, mortality, growth, age distribution, migration, and vital statistics and the interaction of all these with social and economic conditions".
Based on vital statistics reporting and special surveys of population size and density; it measures trends over time.
Includes indices such as fertility, birth, and death rates; rural–urban residential patterns; marriage and divorce rates and migrations; and their interaction with social and economic conditions.
Vital statistics include births; deaths; and population by age, gender, location of residence, marital status, socioeconomic status (SES), and migration. Birth data are derived from mandatory reporting of births and mortality data from compulsory death certificates.
Census: a survey covering the entire population of a defined geographic, political, or administrative entity.
It is an enumeration of the population, recording the identity of all people in every residence at a specified time.
Provides important information on all members of the household, including age, date of birth, gender, occupation, national origin, marital status, income, relation to head of the household, literacy, education level, and health status (e.g., permanent disabling conditions).
Covers residents of health and social facilities such as nursing homes or similar care facilities.
May assign people according to their location at the time of the enumeration (de facto) or to the usual place of residence (de jure).
Census tract: the smallest geographic area for which census data are aggregated and published.
Intercensus surveys are systematically collected information sets, without prior hypothesis, usually by questionnaires with questions carefully composed and tested for validity and consistency.
They may include interviews, biological samples, and physical examination.
Example: US National Health and Nutrition Examination Surveys (NHANES)
Demographic transition is a long-term trend of declining birth and death rates, resulting in substantive change in the age distribution of a population.
Population age and gender distribution is mainly affected by birth and death rates, as well as other factors such as migration, economics, war, political and social change, famine, or natural disasters.
Biodemography, the study of the senescent process, focuses on aspects such as the length of life, the length of healthy life, and the limits to the lifespan.
Stages of demographic transition:
Traditional – high and balanced birth and death rates.
Transitional – falling death rates and sustained birth rates.
Low stationary – low and balanced birth and death rates.
Graying of the population – increased proportion of elderly people as a result of decreasing birth and death rates, and increasing life expectancy.
Regression – low birth rates, migration, or increasing death rates among young adults due to trauma, acquired immunodeficiency syndrome (AIDS), early cardiovascular disease (CVD) mortality, or war can result in a steady or declining population (i.e., demographic regression).
Factors in fertility decline and increasing longevity:
Factors in Fertility Decline
Education, especially of women.
Decreasing infant and child mortality, reducing pressure for more children to ensure survivors.
Economic development, improved standards of living, rising expectations, and family income levels.
Urbanization – family needs and resources change compared to rural society.
Birth control methods – safe, inexpensive, supply, accessibility, and knowledge.
Government policy promoting fertility control as a health measure.
Mass media can raise awareness of birth control and aspiration to higher standards of living.
Health system development and improved access to medical care.
Changing economic status, social role, and self-image of women.
Changing social, religious, political, and ideological values.
Factors in Increasing Longevity
Increasing family income, education level, and standards of living.
Improved nutrition including improved food supply, distribution, quality, and nutritional knowledge.
Control of infectious diseases.
Reduction in non-infectious disease mortality.
Adequacy of safe food and water, sewage and garbage disposal, adequate housing conditions.
Medical care services with improved access and quality.
Health promotion and education activities of the society, community, and individual.
Social security systems, child allowances, pensions, unemployment insurance, national health insurance.
Improved conditions of employment and recreation, economic and social well-being.
Commonly Used Fertility Rates:
Crude birth rate (CBR) – the number of live births in a population over a given period, usually one calendar year, divided by the midyear population of the same jurisdiction, multiplied by 1000.
CBR = (Live Births / Midyear Population) * 1000
Total fertility rate (TFR) – the average number of children that a woman would bear if all women lived to the end of their childbearing years and bore children according to age-specific fertility rates; most accurately answering the question “how many children does a woman have, on average?”
Population Pyramid
Provides a graphic display of the percentage of men and women in each age group in a total population.
A wide population base and a high birth rate in a country or region result in a large percentage of its population being under 15 years of age; when accompanied by limited economic resources, this is a formula for continued poverty.
Aging of the population represents an increase in the over-65 population to some 13 percent of the population.
Life Expectancy
Life expectancy is an important health status indicator based on the average number of years a person at a given age may be expected to live given current mortality rates.
Can be measured at birth (age 0), which is most commonly used for national and international comparisons.
Also reported at other specific ages, representing expected survival time once a person has reached that age; for example, at age 15, 60, or 75 by gender and by ethnic group, or by specific medical conditions such as cancer of the colon, myocardial infarction, and others.
Life expectancies are as much as 5 years longer in other high-income countries such as Singapore, Japan, Israel, Scandinavia, Canada, and the UK than for the US population.
Life expectancy is also used in chronic disease epidemiology to summarize patterns of mortality and survival in a population, such as people with breast cancer.
Demography is becoming a major political and social issue in countries where demographic transition is resulting in major shifts in population make-up, and less severely in Western European countries.
International migration has important demographic, economic, social, cultural, political, and health implications for the migrants’ original and adopted countries.
Population projection is fraught with many uncertainties such as fertility rates, death rates, life expectancy, and economic, cultural, and political factors.
World population growth is uneven, as high- and medium-income countries have reduced their birth rates to near or below population replacement levels, while low-income countries continue with high birth rates, so that world population growth will continue to levels that will challenge the provision of basics such as water, food, and economic development.
Epidemiology
Epidemiology is the study of health events in a population.
Goals:
To eliminate, contain, or reduce health problems and related consequences.
To prevent the occurrence or recurrence of problems.
Methods:
Describe the distribution and size of disease problems in human populations.
Identify etiological (i.e., the cause of disease) processes and factors involved in the pathogenesis of disease.
Provide data essential to the planning, implementation, and assessment of services for the prevention, control, and treatment of disease and to establish priorities among these services.
Ethical Principles: Autonomy, Beneficence, Non-maleficence, and Justice.
Current Challenges of Epidemiology: Addressing health inequities and promoting health equity in all fields of disease and health.
A challenge of epidemiology is to measure the contribution of health care to population health outcomes with precision, given the often multifactorial nature of many outcomes.
Variables are “any attribute, phenomenon, or event that can have different values”.
Health-related states and events include diseases, causes of death, behavior such