For the following name the unit of analysis and identify the study design (ecolo
ID: 3334199 • Letter: F
Question
For the following name the unit of analysis and identify the study design (ecologic, cross-sectional, case-control, historical cohort or prospective cohort study).
a) A group of strict vegetarians were compared to non-vegetarians on their respective risks for several diseases believed to have dietary causes. They were identified on college campuses and then followed forward in time for twenty years with periodic questionnaires and matching to nation-wide disease registries.
b) A study was conducted to examine the pattern of mortality rates from influenza over time throughout the 20th century in the United States. Cause-specific mortality rates for every flu season beginning in 1900-1901 and ending in 2003-2004 (with the exception of 1905-1909, for which data could not be located) were assembled and compared. With the exception of the 1918-1919 flu season, the pattern was definitely a decreasing secular trend throughout the 20th and early 21st centuries.
c) The apgar scores (a system of scoring an infant’s physical condition after birth) of infants were separated into high and low. Medical records were then checked to ascertain if the two groups differed in the type of anesthesia their mothers had received during their births.
d) In 2002 the computer records of 1,099 children from an urban pediatric practice in New Orleans born between April 1, 1998 and June 1, 1999 were examined. It was found that 568 had been vaccinated against rotavirus infection, while 513 had not. Hospital records were also reviewed to determine rates of hospitalization for rotavirus infections in this group of children between October 1998 and June 2001. The incidence of rotavirus hospitalization was 0.34 per 100 child-years for the entire sample. It was 0.52 per 100 child-years for unvaccinated (no doses) children, 0.20 per 100 child-years for partially vaccinated (one or two doses) children and 0 per 100 child-years for fully vaccinated (three doses) children.
e) In a survey of 3,084 Native Americans, approximately two thirds were found to have experienced some form of lifetime trauma.
Explanation / Answer
a)
Unit of analysis: Veg and Non-vegeterians
Study Design: Prospective Cohort Study
b)
Unit of analysis: Deaths due to flu
Study Design: Historical cohort study
c)
Unit of analysis: Apgar scores
Study Design: Case-control Study
d)
Unit of analysis: Children vaccinated/not vaccinated against rotavirus infection
Study Design: Cross-sectional Study
e)
Unit of analysis: Americans
Study Design: Ecological Study