In order to maximize understanding of biostatistics and its applications, a great practice for students is to review medical research studies. When reviewing medical research studies, it is important for students to recognize the type of study (randomized clinical trial, case control study, cohort study, or longitudinal study) employed and whether the study is retrospective or prospective. Understanding the type of research used and whether it is retrospective or prospective will aid a student in determining a study’s validity in an objective manner. This paper will briefly describe the preceding terms and then go on to applying these terms to five medical research study abstracts that I will describe in detail while pointing out each study’s potential strengths and weaknesses.
Types of Studies
There are four types of studies that can be used in the design of a medical research study, those being a randomized clinical trial, case control study, cohort study, and longitudinal study. A randomized clinical trial study is “a clinical study where volunteer participants with comparable characteristics are randomly assigned to different test groups to compare the efficacy of therapies” (Randomized Clinical Trial, 2011, para.1). A case control study is epidemiological study used to identify factors that may contribute to a medical illness by comparing those who have the disease or condition of interest (the cases) with those who do not have the disease or condition of interest (the controls). A cohort study is “a study in which subjects who presently have a certain condition and/or receive a particular treatment are followed over time and compared with another group who are not affected by the condition under investigation” (What is Cohort Research?, 2011, para.1). A longitudinal study is a study that follows patients over a prolonged period of time. Some sources also describe a longitudinal study as one in which the same patients are examined on two or more occasions.
A study can either be retrospective or prospective. Retrospective studies look backwards in time and examines exposures to suspected risk or protection factors in relation to an outcome that is established at the start of the study. In contrast, a prospective study looks forward in time and watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s).
Research Study Abstract #1
The first medical research study abstract that will be described in detail is “A Large Study of Long-Term Daily Use of Adult-Strength Aspirin and Cancer Incidence” by Eric J. Jacobs, Michael J. Thun, Elizabeth B. Bain, Carmen Rodriguez, S. Jane Henley, and Eugenia E. Calle.
This study shows evidence that aspirin use correlates with lowered risks of colon cancer and possibly several other cancers, including prostate and breast cancer. The study method examined associations between long-term daily use of adult strength aspirin (325 mg/day) measuring overall cancer incidence and incidence of 10 types of cancer among 69810 men and 76303 women. These men and women, who were relatively elderly, took part in the Cancer Prevention Study.
Since aspirin use was reported at enrollment in 1992-1993 and updated in 1997, 1999, and 2001, this is a cohort study. Individuals were already classified as groups at the beginning of the study into those who were taking 325 mg/day of aspirin and those who were not. The study is also retrospective in nature because it looked at survey data that was already provided by the American Cancer Society.
Results of the experiment showed that during a follow up in 2003, that Long-term (5 years) daily use of adult-strength aspirin, in comparison with no aspirin use, was associated with lower overall cancer rate in men (multivariable-adjusted RR = 0.84, 95% confidence interval [CI] = 0.76 to 0.93). Since the confidence interval does not include 1 and RR (rate ratios) for men was < 1, results are deemed statistically significant. A non-statistically significantly lower overall cancer rate was reported in women (multivariable-adjusted RR = 0.86, 95% CI = 0.73 to 1.03). Although the RR (rate ratios) for women was < 1, the confidence interval includes 1; results a deemed to be non-significant because variation can account for the observed correlation. Results also show that long-term daily aspirin use correlated with lower incidence that was statistically significant of colorectal cancer (RR = 0.68, 95% CI =0.52 to 0.90 among men and women combined) and prostate cancer prostate cancer (RR =0.81, 95% CI = 0.70 to 0.94). Non-statistically significantly lower overall female breast cancer (RR = 0.83, 95% CI = 0.63 to 1.10) was shown by the results.
Since this study is a retrospective cohort study, it does have several specific strengths and weaknesses. Strengths are that it is good for displaying multiple outcomes and is relatively inexpensive. Major weaknesses include that the investigator has little or no control over exposure and outcome, the temporal relationship is often difficult to determine, it requires large samples for rare outcomes, and the comparability between exposed and unexposed is difficult to achieve.
Research Study Abstract #2
The second medical research study abstract that will be described in detail is “Effects of Immediate Versus Delayed Pushing during Second-Stage Labor on Fetal Well-Being: A Randomized clinical trial” by Kathleen Rice Simpson and Dotti C. James.
This study shows evidence that it is more favorable for the well-being (in terms of fetal oxygen desaturation/saturation and variable decelerations of the fetal heart rate) of an infant for mothers at 10-cm cervical dilation to delay pushing until the woman feels the urge to push versus being coached to immediately start pushing at 10-cm cervical dilation. The study also shows that women who pushed immediately had more perineal lacerations. No differences were shown in the results between pushing and delayed pushing in length of labor, method of birth, Apgar scores, or umbilical cord blood gases.
Since women were randomly allocated to receive one or other of the alternative treatments under study (to push or delay pushing) this is a randomized clinical trial. It is also prospective in nature because it looked forward in time and watched for outcomes.
Results of the experiment showed significant difference between groups in fetal oxygen desaturation during the 10-cm cervical dilation (immediate: M = 12.5; delayed: M = 4.6) F (1, 43) = 12.24, p =.001, and in the number of >=2-min epochs of fetal oxygen saturation <30% (immediate: M = 7.9; delayed: M = 2.7), F (1, 43) =6.23, p =.02. There were more variable decelerations of the fetal heart rate in the immediate pushing group (immediate: M = 22.4; delayed: M = 15.6) F (1, 43) = 5.92, p =.02. Women who immediately at pushed 10-cm cervical dilation had more perineal lacerations (immediate: n = 13; delayed: n = 5) [chi] 2 (1, N = 45) = 6.54, p =.01. Assuming that the alpha is.05; the p-values fall well below the threshold and are deemed to be statistically significant; in other words, the null hypothesis is rejected in variable decelerations of the fetal heart rate, fetal oxygen saturation, and perinatal lacerations.