1 Cross-sectional studies Dr Hardeep Kaur Associate Professor University College of Nursing BFUHS

2 Definition A cross-sectional studies –a type of observational study –the investigator has no control over the exposure of interest (eg. diet). It involves –identifying a defined population at a particular point in time –measuring a range of variables on an individual basis e.g. include past and current dietary intake –At the same time measuring outcome of interest e. g. obesity

PRD-3 Definition Measurement of exposure of interest and outcome of interest is carried out at the same time (e.g. Obesity and Hypertension) There is no in-built directionality as both exposure and outcome are present in the study subject for quite some time

PRD-4 Cross-sectional studies Deals with the situation existing at a given time (or during a given period) in a group or population These may be concerned with: –The presence of disorders such as diseases, disabilities and symptoms of ill health –Dimensions of positive health, such as physical fitness –Other attributes relevant to health such as blood pressure and body measurements –Factors a/w health & disease such as exposure to specific environmental exposure or defined social & behavioral attributes and demographic attributes –Determining the workload of personnel in a health program as given by prevalence

2 Deciding which one to use The investigator observes the events without altering them Decision # 1 Alter the events under study? The investigator applies an intervention, & observes the effect on the outcome NO Yes Observational study Experimental study Example: Comparing the history of needle sharing among IV drug abusers who have HIV antibodies with those who do not Example: Impact of health education on needle sharing habits

3 Deciding which one to use For observational studies Decision # 2 Make measurements on more than one occasion? Each subject is examined on only one occasion Each subject is followed over A period of time NO Yes Cross-sectional study Longitudinal study Example: Study of needle sharing habits and HIV antibodies measured at the same time Example: Cohort study that assesses current needle sharing habits of group of IV drug abusers and observes who subsequently develop HIV antibodies

PRD-7 Cross-sectional studies May be –Descriptive –Analytical or –Both At descriptive level, it yields information about a single variable, or about each of number of separate variables in a study population At analytic level, it provides information about the presence and strength of associations between variables, permitting testing of hypothesis

PRD-8 Features Essential feature of cross-sectional studies -They collect information relating to a single specified time But, often extended to include historical information which leads to demonstration of statistical associations with past experience e.g. investigation of an epidemic.

PRD-9 Synonyms Instantaneous study Prevalence study Simultaneous study

PRD-10 Steps in cross-sectional studies

PRD-11

PRD-12 Uses of CS studies.. The findings may be used to promote the health of the population studied i.e. can be used as tool in community health care Can contribute to clinical care Can provide “new knowledge” The uses are not mutually exclusive & single study can fulfill more than one purpose

PRD-13 Uses in community health care Community diagnosis –Health status –Determinants of health & disease –Association between variables –Identification of groups requiring special care Surveillance Community education & community involvement Evaluation of community’s health care

PRD-14 Uses in clinical practice Individual & family care Community oriented primary care

PRD-15 Studies yielding “new knowledge” Studies of growth & development Studies of etiology Program trials

PRD-16 Cross-Sectional Studies Advantages Cheap and quick studies. Data is frequently available through current records or statistics. Ideal for generating new hypothesis.

PRD-17 Cross-Sectional Studies Disadvantages The importance of the relationship between the cause and the effect cannot be determined. Temporal weakness: –Cannot determine if cause preceded the effect or the effect was responsible for the cause. –The rules of contributory cause cannot be fulfilled.

PRD-18