Applied Biostatistics for the Health Sciences. Richard J. Rossi
diagnosis with stage IV melanoma.
4 d. Explanatory variables in this study are age, sex, race, and tumor thickness.
5 e. The parameter of interest in this study is the average survival time after diagnosis with stage IV melanoma.
6 f. Treatments are the two different doses of interferon.
7 g. The sample size is n = 150.
1.2.2 Biomedical Studies
There are many different research protocols that are used in biomedical studies. Some protocols are forward looking studying what will happen in the future, some look at what has already occurred, and some are based on a cohort of subjects having similar characteristics. For example, the Framingham Heart Study is a large study conducted by the National Heart, Lung, and Blood Institute (NHLBI) that began in 1948 and continues today. The original goal of the Framingham Heart Study was to study the general causes of heart disease and stroke, and the three cohorts that have or are currently being studied in the Framingham Heart Study are as follows.
1 the original cohort that consists of a group of 5209 men and women between the ages of 30 and 62 recruited from Framingham, Massachusetts.
2 The second cohort, called the Offspring Cohort, consists of 5124 of the original participants’ adult children and their spouses.
3 the third cohort that consists of children of the Offspring Cohort. The third cohort is recruited with a planned target study size of 3500 grandchildren from members of the original cohort.
Two other large ongoing biomedical studies are the Women’s Health Initiative (WHI), which is a research study focusing on the health of women, and the National Health and Nutrition Examination Survey (NHANES), which is designed to assess the health and nutritional status of adults and children in the United States.
Several of the commonly used biomedical research protocols are described below.
A cohort study is a research study carried out on a cohort of subjects. Cohort studies often involve studying the patients over a specified time period.
A prospective study is a research study where the subjects are enrolled in the study and then followed forward over a period of time. In a prospective study, the outcome of interest has not yet occurred when the subjects are enrolled in the study.
A retrospective study is a research study that looks backward in time. In a retrospective study, the outcome of interest has already occurred when the subjects are enrolled in the study.
A case–control study is a research study in which subjects having a certain disease (cases) are compared with subjects who do not have the disease (controls).
A longitudinal study is a research study where the same subjects are observed over an extended period of time.
A cross-sectional study is a study to investigate the relationship between a response variable and the explanatory variables in a target population at a particular point in time.
A blinded study is a research study where the subjects in the study are not told which treatment they are receiving. A research study is a double-blind study when neither the subject nor the staff administering the treatment know which treatment a subject is receiving.
A clinical trial is a research study performed on humans and designed to evaluate a new treatment or drug or to investigate a specific health condition.
A randomized controlled study is a research study in which the subjects are randomly assigned to the treatments with one of the treatments being a control treatment; a control treatment may be a standard treatment, a placebo, or no treatment at all.
It is important to note that a research study may actually involve more than one of these protocols. For example, a longitudinal study is often a cohort study, a case–control study is a retrospective study, a longitudinal study is a prospective study, and a clinical trial may be run as a double-blind randomized controlled study. Also, the nature of a particular research study will dictate the research protocol that is used. Finally, of all of the study protocols, the randomized controlled study is the gold standard in biomedical research because it provides more control over the external factors that can bias the results of a study.
Most of the medical journals that publish biomedical research require the authors of an article to describe the research protocol that was used in their study. In fact, during the peer-review process a journal article undergoes prior to publication, the research protocol will be carefully scrutinized and research based on poor research protocols will not be published. Several examples of the different research protocols used in published biomedical research articles are given in Examples 1.3–1.7.
In the article “A prospective study of coffee consumption and the risk of symptomatic gallstone disease in men” published in the Journal of the American Medical Association (Leitzmann et al., 1999), the authors reported the results of a prospective cohort study designed to investigate whether coffee consumption helps prevent symptomatic gallstone disease. This study consisted of n = 46, 008 men, aged 40–75 years in 1986, without any history of gallstone disease, and the subjects were monitored for a 10-year period from 1986 to 1996.
Example 1.4
In the article “Hospitalization before and after gastric bypass surgery” published in the Journal of the American Medical Association (Zingmond et al., 2005), the authors reported the results of a retrospective research study designed to investigate the amount of time spent in a hospital 1–3 years after an individual receives a Roux-en-Y gastric bypass (RYGB). This study consisted of n=60,077 patients who underwent RYGB from 1995 to 2004 in California.
Example 1.5
In the article “Pesticides and risk of Parkinson disease: a population-based case–control study” published in the Archives of Neurology (Firestone et al., 2005), the authors reported the results of a case–control research study designed to investigate association between occupational and home-based pesticide exposure and idiopathic Parkinson disease. This study consisted of 250 subjects with Parkinson’s disease and 388 healthy control subjects.
Example 1.6
In the article “Randomized, double-blind, placebo-controlled trial of 2 dosages of sustained-release bupropion for adolescent smoking cessation” published in the Archives of Pediatric and Adolescent Medicine (Muramoto et al., 2007), the authors reported the results of a randomized controlled double-blind research study designed to investigate the efficacy of sustained release of bupropion hydrochloride for adolescent smoking cessation. This study consisted of n = 312 subjects recruited through media and community venues from March 1, 1999 to December 31, 2002, who were aged 14–17 years, smoked at least six cigarettes per day, had an exhaled carbon monoxide level of 10 ppm or greater, had at least two previous quit attempts, and had no other current major psychiatric diagnosis.
In the article “Antidepressant efficacy of the antimuscarinic drug scopolamine: a randomized, placebo-controlled clinical trial” published in Archives of General Psychiatry (Furey et al., 2006), the authors reported the results of a double-blind, placebo-controlled, dose finding clinical trial designed to investigate the antidepressant efficacy of scopolamine. This study consisted of n = 19 currently depressed outpatients aged 18–50 years with recurrent major depressive