Epidemiological Study Designs - Assignment Example

Factors like age can have direct links to diseases where very young or very old people may be more susceptible to certain diseases. Factors like religion have indirect links to diseases wherein certain religious practices can make a person more or less susceptible to diseases.

2. Place (Where were they affected?): This includes information like geographic location, presence of agents or vectors, climate, geology, population density, economic development, nutritional practices, and medical practices. This information is essential for investigating a known disease outbreak and also for the surveillance system to detect an outbreak.

3. Time (When were they affected?): This includes information like calendar time, time since an event, physiological cycles, seasonality, and temporal trends. This information is important to determine if an outbreak has occurred or if the increase in incidence is caused due to natural increases over time or seasonal variations in symptoms.
Person, Place, and Time-Related to Observational Study Design
Observational study design refers to epidemiological studies that involve observing individuals or measuring certain outcomes without making any attempt to influence the outcome (Aschengrau & Sage, 2003). In this study, the investigator passively observes the course of nature unlike the experimental study design wherein the investigator actively manipulates certain variables. Descriptive observational studies involve the analysis of disease patterns by studying the causes, prevention, and treatment of diseases. The data for this study is collected in terms of the characteristics of person, place, and time using surveys or surveillance programs.
In the context of dental public health consider an observational study conducted by Arnold (1957) about the effectiveness of fluoridation of water in preventing and controlling dental caries. In this study, the three major elements are:
Person: All children between the ages of 5 and 16
Place: Elementary and secondary schools in Grand Rapids, Michigan
Time: 11 years from 1944 to 1955

The authors of this study merely observed the rate of dental caries in school-going children between the ages of 5 and 16 for 11 years. A baseline data was collected in 1944 before the fluoridation of water was initiated in Grand Rapids, Michigan and the target population was closely observed for 11 years till 1955. The results revealed that the prevalence of dental caries was reduced by 60 to 65% among children who were born after the water fluoridation program was initiated. Water fluoridation was also found to have a significantly positive effect on teeth that were formed or erupted before the implementation of the fluoridation program. This study, therefore, helped to determine how the rate of dental caries changed over time after the fluoridation of water was implemented.
Person, Place, and Time-Related to Experimental Study Design
Experimental study design refers to epidemiological studies that involve the manipulation of one or more variables to determine their effect on a dependent variable (Aschengrau & Sage, 2003). The group that receives the agent is called the treatment group while the group that does not receive the agent is called the control group. Analytical research study designs help to investigate the role of an agent in the prevention or treatment of a disease. The data for this study is collected in terms of the characteristics of person, place, and time whereby the investigator manipulates the exposure of subjects to the agent.
In the context of dental public health consider an experimental study conducted by Sankaranarayanan et al. (2005) about the effects of screening on oral cancer mortality in Kerala, India, where alcohol and tobacco consumption is higher than that in developed countries. In this study, the three major elements are:
Person: Healthy adults (men and women) over 35 years
Place: Kerala, India

Time: 8 years from 1996 to 2004
The study aimed to measure the effects of visual screening of oral cancer in a cluster randomized control trial. Participants were healthy adults who were above the age of 35 years. The agent that was manipulated was a visual screening of oral cancer. Participants in the treatment group received the visual screening of oral cancer while those in the control group did not receive it. Individuals in the treatment group who tested positive on the screen were referred for a clinical examination to doctors who followed it up with biopsy and treatment. The compliance rate of referrals in the treatment group was 63%. Individuals in the control group received standard care. After 8 years, the oral cancer rates in the treatment group were compared with those in the control group. Read More