Cross-Sectional Studies

Nomenclature and Categorization

The purpose of many cross-sectional health studies is to describe the prevalence of a disease (e.g., the number of individuals with lung cancer in a community), the exposure to a particular risk factor (e.g., the number of individuals who smoke), or the [Page 265]health outcome (e.g., changes in death, disease, disability, discomfort, or dissatisfaction) for a specific population; hence cross-sectional studies are also commonly referred to as prevalence studies. Cross-sectional or prevalence studies are also referred to as surveys, which emphasizes the fact that they are conducted at one time. Beyond this nomenclature is the categorization and classification of cross-sectional studies, which often differs by author. The various classification schemes are summarized below.

Most of the healthcare literature classifies cross-sectional studies as descriptive studies, along with case reports, case-series reports, and surveillance studies. Descriptive studies in general collect information from individuals (except ecological studies, which are sometimes placed in this category), and they attempt to describe the characteristics of people or a population.

Other classification schemes divide all studies into either experimental studies (where the randomized controlled clinical trial is the gold standard) or observational studies (which include cross-sectional, case-control, cohort, and ecological studies). Occasionally observational studies are subclassified into descriptive studies (i.e., case reports, case-series reports) and analytical studies (i.e., ecological, cross-sectional, case-control, and cohort studies)—where the criterion for classification is whether or not the information collected requires data analysis to develop conclusions.

Yet other classification schemes simply divide all studies into either cross-sectional studies or longitudinal studies—one point in time measurements (i.e., cross-sectional) versus repeated measures or time series measurements over a length of time (i.e., longitudinal, such as a cohort study). However, when serial cross-sectional studies of the same population are linked, such as the U.S. Census of Population for several different years, a modified form of longitudinal study is created (i.e., modified because the same people are not studied each year of the census due to migration, immigration, and births and deaths).

Uses of Cross-Sectional Studies

Cross-sectional studies are often used to determine the current health status of a population (e.g., the total number of people with HIV/AIDS). They are often used to establish baseline information, which can be used for health services planning purposes and to make public policy decisions.

A large number of government agencies and private organizations conduct cross-sectional health studies. The federal agency that conducts the largest number of such studies is the National Center for Health Statistics (NCHS), which is part of the National Centers for Disease Control and Prevention (CDC). The NCHS conducts, for example, the National Ambulatory Medical Care Survey (NAMES), the National Health Interview Survey (NHIS), the National Health and Nutrition Examination Survey (NHANES), the National Hospital Discharge Survey (NHDS), the National Home and Hospice Care Survey (NHHCS), and the National Nursing Home Survey (NNHS).

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