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By Professor Omar Hasan Kasule Sr.
Learning Objectives
· Definition, classification, and uses of various rates and proportions: vital, demographic, and morbidity
· Crude rates, specific rates, and standardized/adjusted rates.
· Population pyramid: age and sex-structure of different populations
Key Words and Terms
· Demographic, life table
· Demographic, rates
· Demographic, shift
· Epidemiological, transition
· Health status indicators
· Life, expectancy
· Population, life tables
· Population, pyramid
· Rate, birth rate
· Rate, crude rate
· Rate, death rate
· Rate, incidence rate
· Rate, morbidity rate
· Rate, mortality rate
· Rate, pregnancy rate
· Rate, specific rate
· Rate, standardized rate
· Rate, vital rate
· Ratio, mortality ratio
· Statistics, vital statistics
1.1 Vital statistics
Vital statistics (birth, death, marriage, and divorce) are from mandatory reporting. They generate hypotheses for further investigation. They are analyzed in conjunction with ecologic or environmental data.
1.2 Birth
Crude Birth Rate (CBR) is births per 100,000 of mid-year population per year.
Premature Birth rate is births at gestation age 28-38 weeks per 1000 live births per year.
Low birth weight rate is births < 2500 g per 1000 live births per year.
Very low birth weight rate is births < 1500 g per 1000 live births per year.
1.3 Death
Crude Death Rate (CDR) is deaths in a year per 100,000 of mid-year population.
Proportional Mortality Ratio (PMR) is deaths of a specified kind as a proportion of the total number of deaths.
Case-fatality ratio is the proportion of deaths from persons with a specified disease condition.
Fetal death rate is deaths >= 20 weeks per 1000 births (live births + still births) per year.
Fetal death ratio is death =<20 weeks per 1000 1000 live births.
The abortion ratio is number of induced abortions per 1000 live births.
Infant Mortality Rate (IMR), the most important indicator of community health, is deaths at ages 0-12 months per 1000 live births per year.
Total Neonatal Mortality Rate is deaths within 1-28 days of birth per 1000 live births.
Early Neonatal Mortality Rate is deaths within 7 d of birth per 1000 live births per year.
Late Neonatal Mortality Rate is deaths at age 7-28 days of birth per 1000 live births per year.
Post Neonatal Mortality Rate is deaths aged 28days -1 year of birth per 1000 live births per year.
Peri-natal Mortality Rate is deaths aged > 28 weeks up to 7 days of birth per 1000 total births (live births + stillbirths) per year.
Perinatal mortality ratio is the number of fetal deaths >= 28 weeks + deaths within one week of birth per 1000 live births.
Maternal Mortality Rate is deaths in pregnancy or within 42 days of delivery per 100,000 births.
1.4 Marriage and divorce
Marriage rate is marriages in a year per 1000 of population.
Divorce rate is divorces in a year per 1000 or population or per 1000 marriages.
Sources of morbidity data are: Compulsory notification data, diseases registries (cancer, substance abuse, birth defects, mental, congenital anomalies), Hospital discharge data, health service utilization indices, health status indicators, Ministry reports, and Health, Nutrition and Morbidity Surveys. Both seasonal and cyclic trends in disease rates must be studied. Data from medical records gives information on clinical, demographic, sociologic, economic, administrative, and behavioral variables.
Infectious disease notification is required for (a) access to treatment (b) local administrative action (c) epidemic control (d) research (e) aid diagnosis.
Examples of notifiable infectious diseases: (a) GIT infections: hepatitis, cholera ,typhoid & paratyphoid, amebic dysentery & bacillary dysentery (b) food poisoning (c) respiratory infections: tuberculosis, diphtheria (d) parasites: malaria (e) sexually transmitted td: syphilis, HIV (f) viral: dengue
Examples of notifiable non-infectious diseases: (a) industrial accidents (b) non-industrial accidents (road traffic accidents, sports and recreation accidents, home accidents)
Parameters of child growth and development: (a) Nutritional status: weight for height, BMI (b) Low birth weight rate (c) Mean length 0-1 year; mean height 1-18 years (d) Mean weight 0-1 year, 1-18 years (e) Chest Circumference (f) % immunized fully. School health: vision defects, hearing defects, and dental defects. Food intake (Energy kcal/day, Protein g/day, Fat g/day, and Minerals (Ca, Fe)
Medical facilities & personnel: (a) # hospital beds per 10,000 population (b) Hospital stay: patien-days/100,000 population (c) Bed occupancy: # bed-days per year (d) Admissions and discharges per 100,000 of population (e) # outpatient visits per year (f) Physicians, dentists, pharmacists, midwives, & nurses per 100,000 population
Hospital statistics: admissions, discharges, diagnoses, and procedures
2.1 Demographic Rates
Total Fertility Rate (TFR) is births per year 1000 women aged 15-44 in mid-year population. Replacement level is TFR of 2.1.
Gross reproductive rate is reproductive rate computed for girls only.
Net reproductive rate is the proportion of girls surviving to the reproductive age out of 1000 live births.
2.2 Population pyramid
Population is described by age, sex, race/ethnicity, marital status, education, and occupation.
Population pyramids reflect both birth and death rates. They display population structure by age, and gender.
Population structure and future projection are determined by fertility, mortality, and migration. Population pyramids have a narrow base and a wide top in industrial countries and a wide base and a narrow top in non-industrialized ones. Atypical pyramids are due to war, genocide, and migration.
Demographic shift/transition is change in population structure with falling birth and death rates.
Epidemiologic transition is change in disease patterns as the population structure changes. It follows demographic transition.
Life tables showing life expectancy at various ages are used for actuarial, pension, & annuities computations; assessing health services; and computing Potential Years of Life Lost (PYLL).
Life expectancy at birth, a sensitive indicator of the life of the community, indicates current death rates. It is lower at birth than at age 1 year due to high IMR in the first year of life.