Johns Hopkins Nursing Evidence-Based Practice Thrid Edition: Model and Guidelines

6 Evidence Appraisal: Research 115

Figure 6.3 Illustration of a prospective cohort study.

Teenagers who smoke

Develop
lung cancer

Do not develop

lung cancer

Teenagers who do not

smoke

Develop

lung cancer

Do not develop

lung cancer

Example: Nonexperimental Descriptive Cohort Design

A group of researchers in the United Kingdom used Clinical Practice Research

Datalink files from 2004 to 2014 to study the probability of an obese person

attaining normal body weight or a 5% reduction in body weight. The study

included 76,704 obese men and 99,701 obese women. In examining this cohort,

the probability of attaining normal weight or maintaining weight loss was low.

The annual probability of attaining normal weight was 1 in 210 for men and 1

in 124 for obese women, not including the morbidly obese. The researchers

concluded that obesity treatment programs grounded in community-based weight

management programs may be ineffective (Fildes et al., 2015).

Cross-sectional studies involve the collection of data at one particular point in

time. These studies collect a representative sample and classify by outcome and

risk factor simultaneously. The basic question asked in cross-sectional research is,

“What are the characteristics of a population at a single point in time?” In epide-

miology, the researcher starts with a defined population and gathers data on the

presence or absence of exposure and the presence or absence of disease for each

individual at a particular point. Prevalence studies employ epidemiological cross-

sectional designs. In other types of studies using a cross-sectional design, the re-

searcher looks at variables in a population at a single point.