Chapter FourOccurrence of disease with respect to person, place, & time is central to epidemiologyDescriptive vs. Analytic- Descriptive Epidemiology: concerned with characterizing the amount and distribution of a disease within a populationo Evaluate/compare trends in health and disease among countries o Provide basis for planning, provision, & evaluation of health serviceso Identify problems for analytic studies- Analytic Epidemiology: determinant of diseaseo Reason for high or low frequency of disease in population subgroupsCharacteristics of Persons- Ageo One of the most importanto Use age-specific rates when comparing disease burdeno Childhood= congenital problems, infectious and communicable disease (measles, mumps, chicken pox)o Teens= accident, violence, suicide, pregnancy, substance abuseo Adults= accident, homicide, suicide, cancer, heart disease, HIVo Older Adults= chronic diseases (heart disease)o 4 Reasons For Age Associations Validity of diagnoses- Age- specific incidence rates among elderly often inaccurate Multimodality of trends- Age-specific distributions can be linear or multimodal Latency effects- Age effects on mortality may reflect long latency period betweenenvironmental exposures and subsequent development of disease “Human Biological Clock”- Endogenous process associated with increased vulnerability to disease- Sexo Males Higher all-cause mortality rates Develop severe forms of chronic diseaseo Females Higher morbidity rates CHD is leading cause of mortality in women Resist lifestyle changes Minority women have higher morbidity than men- Marital Statuso Married- lower mortality and morbidity than singleo Divorced women- adverse health outcomeo Never married- likely overweighto Protective factor- may provide an environment conducive to healtho Selective factor- people who marry may be healthier to begin with- Ethnicityo African Americans Highest mortality rate High BP (stress or diet)o American Indians Chronic disease Adverse birth outcome Infectious disease (TB/Hep A)o Asians Lower mortality rates Lower CHD and cancer rates- Low fat diet and stress reducing strategies- Acculturation - Modifications that individuals or groups undergo when they come in contact with another country- Evidence of the influence of environmental and behavioral factors on chronic diseaseo Ex- Jap migrants experience shift in rates of chronic disease- Nativity- place of origin of the individual or his or her relatives o Importation of 3rd World disease by immigrants o Programmatic Needs b/c migration: Specialized screening programs (TB & nutrition) Familiarization with formerly uncommon tropical diseaseso Healthy Migrant Effect Younger, healthier persons usually form most of migrants Often difficult to separate environmental influences in the host countryfrom selective factors among those who migrate- Religiono Certain religions prescribe lifestyles that may influence rates Vegetarian diet Abstain from alcohol and tobacco use Lower rates of CHD, reduced cancer risk, lower BP- SESo Lower social class related to excess mortality, morbidity, & disability Work and environmental hazards Material and social deprivation Lack of access to healthcare Negative lifestyle Severe mental illness- Social Causation Explanation (breeder hypothesis)- conditionsassociated with lower social class produce mental illness- Downward Drift Hypothesis- persons with severe mental disorders move to impoverished areasInternational Comparisons of Disease Frequencyo WHO- tracks international variations in rates of diseaseo Infectious and chronic diseases show great variation across countrieso Attributed to climate, cultural factors, dietary habits, and healthcare accesso CHD, hypertension, and diabetes were confined to developed countries, but now occurring more in developing countries as living standards improveo Countries with high economic standards foster behavior implicated in CHD and other chronic diseaseso Infectious disease 5% of death in developed countries 50% of death in underdevelopedpCountrywide Variations in Rates of Diseaseo US comparisons can be made within region, state, countyo Ex: leukemia higher in Midwesto Urban diseases associated with crowding, pollution, and povertyo Ex: lead poisoningo Unique environmental/social conditions o Goiter- iodine deficiency in land-locked areas of USo Reasons:o Gene/environment interactiono Influence of climateo Environmental factors Ex: chemical agents linked to cancerCharacteristics of Timeo Cyclic Fluctuations- periodic changes in frequency of diseases and health conditions over timeo Point Epidemics- response of a group of people in place and time to common source of infection simultaneously (foodborne illness)o Secular Time Trends- gradual changes in frequency of disease over long periods (decline in heart disease)o Cluster- unusual aggregation of health events grouped together in space and timeo Spatial- concentration of disease in specific geographic areao Temporal- post-vaccination