Nutrition and Health surveys/nutrition monitoring; Epidemiology Chapters 5 & 7

History of epidemiology John Snow, 1854 – Cholera outbreak in London – Snow had previously hypothesized cholera was transmitted via water. Two water companies in London – One pulled water down stream from sewage, one from up stream – Deaths occurred around water pumps from the downstream company

Practice of Epidemiology Epidemiology –Initially used to investigate, control, and prevent epidemics of infectious disease Epidemiologists work with other health professionals –to identify causes of disease –to propose strategies for controlling or preventing health problems Can be used to describe a community’s health problems and to determine whether health is improving or getting worse Surveillance methods have been used to monitor preventable causes of birth defects

Epidemiology “the study of the _______ and __________ of health-related states and events in specified populations and the application of this study to control of health problems”

Study—Epidemiology is the basic science of public health. It's a highly quantitative discipline based on principles of statistics and research methodologies. Distribution—Epidemiologists study the distribution of frequencies and patterns of health events within groups in a population. To do this, they use descriptive epidemiology, which characterizes health events in terms of time, place, and person. Determinants—Epidemiologists also attempt to search for causes or factors that are associated with increased risk or probability of disease. This type of epidemiology, where we move from questions of "who," "what," "where," and "when" and start trying to answer "how" and "why," is referred to as analytical epidemiology. Health-related states—Although infectious diseases were clearly the focus of much of the early epidemiological work, this is no longer true. Epidemiology as it is practiced today is applied to the whole spectrum of health-related events, which includes chronic disease, environmental problems, behavioral problems, and injuries in addition to infectious disease. Populations—One of the most important distinguishing characteristics of epidemiology is that it deals with groups of people rather than with individual patients. Control—Finally, although epidemiology can be used simply as an analytical tool for studying diseases and their determinants, it serves a more active role. Epidemiological data steers public health decision making and aids in developing and evaluating interventions to control and prevent health problems. This is the primary function of applied, or field, epidemiology.

Basic Concepts Risk “likelihood that people who are without a disease, but exposed to certain risk factors, will acquire the disease at some point in their lives” –Risk factors may be found in the physical environment or social environment, or they may be inherited. –Other risk factors may be behavioral, such as smoking.

Relative risk “Measure of how much a particular risk factor influences the risk of a specified outcome”- to identify differences in disease rates between exposed and unexposed groups Relative Risk = Rate of condition among exposed divided by rate of condition among unexposed Risk exposure

Incidence “the proportion of group initially free of a disease that develops the disease over a period of time”

Prevalence “the proportion of a group possessing a disease at a specific time”

Epidemiological Method Hypothesis testing –Identify a cause-effect comparison to be tested Explaining research observations –Bias –Chance –Truth

What is Nutritional epidemiology : –Concept diet influences occurrence of diseases –Relatively new the basic method used for > 200 years to identify essential nutrients

Nutrition problems in the past Typical deficiency syndromes –Protein energy malnutrition –Iron deficiency anemia –Goiter –High frequency among those with very low intake –Short latent periods –Can be reversed within days or weeks

Contemporary nutritional epidemiology: Major diseases throughout the world Heart disease Cancer Osteoporosis Cataracts Stroke Diabetes Congenital malformations

Characteristics Multiple causes -diet, genetic, occupational, psychosocial, and infectious factors; levels of physical activity; behavioral characteristics ______________periods -cumulative exposure over many years, or relatively short exposure occurring many years before diagnosis Occur with relatively low frequency -despite a substantial cumulative lifetime risk Conditions not readily ____________ May result from __________ and / or ________ intake of dietary factors Why is it hard to study contemporary nutrition-related disease?

The complex nature of diet has posed an unusually difficult challenge to nutritional epidemiology: –Diet represents an unusually complex set of exposures that are strongly intercorrelated, cannot be characterized as present or absent –Continuous variables often with a rather limited range of variation –Individuals rarely make clear changes in their diet at identifiable points in time; typically eating patterns evolve over periods of years –Individuals are generally not aware of the content of the foods that they eat

Limitation in nutritional epidemiology research Lack of practical methods to measure diet for large number of subjects Dietary assessment methods must be –reasonably accurate –relatively inexpensive Diets of persons within one country are too homogeneous to detect relationships with disease

Types of Epidemiologic Studies 1. _____________ or Correlational Studies –Comparisons of disease rates in populations with the population per capita consumption of specific dietary factors. – Dietary data collected in this type of study are usually __________________:  figures for food produced for human consumption  minus the food that is exported, fed to animals, wasted, or otherwise not available for human consumption.

2. Cross-sectional or Prevalence Studies –Examine the relationships among dietary intake, diseases, and other variables as they exist in populations at a particular time.

Types of Epidemiologic Studies 3. Cohort Studies –A group of people, called a cohort, free from the disease is identified and examined, and then followed for months or even years –Group members are examined periodically to determine which individuals develop the characteristics of interest and which do not. - _____________ - look back in time to reconstruct exposures and health outcomes, or - _____________ - those that follow a group into the future.

Types of Epidemiologic Studies 4. Case-Control Studies –A group of persons with the disease is compared with a group of persons without the disease to compare characteristics, such as previous exposure to a factor, between cases and controls. 5. Controlled Trials –The most rigorous evaluation of a dietary hypothesis is the randomized controlled trial conducted as a double-blind experiment.

Nutritional epidemiology…. The method can also be used to: –Describe the nutrition status of populations or specific subgroups of a population –develop specific programs or services for members of the group whose nutrition status appears to be compromised. –Evaluate nutrition interventions.

National nutrition policy - a set of nationwide guidelines that specify how the nutritional needs of the population will be met. - there is no one federal body or agency with its sole mandate to establish, implement, and evaluate national nutrition policy. U.S. national nutrition policy –Food assistance programs. –National nutrition and health objectives. –Regulations to safeguard the food supply and ensure safe handling of food. –Dietary guidance systems. –Monitoring and surveillance programs. –Food labeling legislation.

National Nutrition Policy Does the U.S. have a national nutrition policy?

Why monitor nations health and nutritional status? Nations monitor health and nutrition status - to decide how to allocate scarce resources - to enhance the quality of life - to improve productivity Nutrition monitoring is a term that includes: –Nutrition assessment –Nutrition monitoring –Nutrition surveillance –Nutrition screening

Background on Nutrition Monitoring in the United States 1909 – USDA starts food supply series 1930s – USDA Household Food Consumption Survey started ( changed name to Nationwide FCS) – Ten State Nutrition Survey (Nation’s first comprehensive survey) 1970s – NHANES I and II pediatric Nutrition Surveillance System 1980s – Joint Nutrition monitoring Evaluation Committee with USDA and DHHS 1990 _ Nutrition Monitoring and Related Research Program (NNMRRP) 2001 – CSFII and NHANES integrated

Types of data _________ data: relate directly to the population served; often collected by the acting agency itself –focus groups, local surveys _________ data: relate to already existing data in either published or unpublished form –NNMRR data

National Nutrition Monitoring System NNMRRP = National Nutrition Monitoring and Related Research Program

National Nutrition Monitoring and Related Research Program (NNMRRP) Established by Congress in 1990 Implementation and coordination of activities by USDA and DHHS Monitoring data are used to assess the dietary, nutritional, and related health status of the population More than 50 surveillance systems are operative

NNMRRP Goals Collect, analyze, and disseminate data… Establish baseline data and uniform standards Provide data to evaluate proposed policy changes

NNMRRP Goals Provide scientific foundation for improving nutritional status and quality of food supply Identify high risk groups to aid program planning

National Nutrition Monitoring System Federally mandated collection and analysis of data on: –national food supply –food composition –food and nutrient consumption –consumer knowledge, attitudes, behaviors –nutritional/health status

National Food Supply U.S. Food Supply Series Quantities available per capita of: –food –kcals available –nutrients

Food Composition USDA Nutrient Data Base Used for: –survey analysis –research –individual use  USDA

Food & Nutrient Consumption Ten State Survey Nationwide Food Consumption Survey (NFCS) Continuing Survey of Food Intakes by Individuals (CSFII)  USDA 5 A Day for Better Health  NCI…

Food and Nutrient Consumption “What We Eat in America Survey” –Dietary interview component of NHANES –Individuals in households, one sample with all levels of income, another of low-income households –Two days of 24 hour dietary recall –Times of eating occasions –Sources of food eaten away from home

Food and Nutrient Consumption Total Diet Study (TDS) –Eight age groups, infant through elderly –Assesses for nutrients and contaminants in foods –Estimates levels of 11 essential minerals –Collects and analyzes 234 foods from retail markets in urban areas

KAB Assessments Behavioral Risk Factor Surveillance System (BRFSS) annually since 1984 designed to examine trends over time. States can readily address urgent and emerging health issues. BRFSS questions focus on: –Not getting enough physical activity –Eating a high-fat, low-fiber diet –Using tobacco and alcohol –Not getting medical care that is known to save lives - e.g. mammograms, Pap smears, colorectal cancer screening, and flu shots - Food frequencies for dietary fat, fruit, and vegetable consumption  CDC Youth Risk Behavior Survey (YRBS) CDC Diet and Health Knowledge Survey (DHKS)  USDA

Nutrition and Health Status National Health and Nutrition Examination Surveys (NHANES I, II, III) “What we eat in America” (integration of NHANES & CSFII) Hispanic Health and Nutrition Examination Survey (HHANES)  DHHS Pediatric Nutrition Surveillance System (PedNSS)  CDC

Food Composition and Nutrient Data Base National Nutrient Data Bank (established in 1892) – updated on a regular basis –Nutrient content of foods –Published tables of food composition –Computerized databases

Food Composition and Nutrient Data Base USDA Nutrient Data Base for Standard Reference (initiated in 1980) – produced from National Nutrient Data Bank –Includes data on food energy, 28 food components, and 18 amino acids for about 5,200 food items –Main source of data for USDA Survey Nutrient Data Base

Food Composition and Nutrient Data Base USDA Survey Nutrient Data Base - updated continuously –Used for analysis of nationwide dietary intake surveys –Includes data on food energy and 28 food components for >7,100 food items

Uses of NMRR Data Assessment of dietary intake Monitoring and Surveillance Regulation Food programs and Guidance Scientific Research Historical trends