Assignment 1
PART A
Question 1. Please read the following abstract and answer the following questions (22 marks)
A study was performed to examine the relationshipbetween breast cancer and working on rotating night shifts during10 years of follow-up in 78 562 women from the Nurses' HealthStudy. Subjects completed questionnaires that comprised items about theirhealth status, medical history, and known or suspected riskfactors for cancer and heart disease. Information was ascertained in 1988 about the total numberof years during which the nurses had worked rotating night shiftswith at least three nights per week. From June 1988 through toMay 1998, 2441 incident breast cancer cases were documented of which 925 of these were among women who had never worked night shift. A total of 736, 015 person-years at risk contributed to the study. Women who hadworked on rotating night shifts accounted for 40.4% ofthe person-years of follow-up. (Adapted from Schernhammer E.S et al., 2001.)
Cases / Person-years at risk / RateWorked Nightshift at least 3 nights per week
Did not work night shift for at least 3 nights per week
TOTAL POPULATION / 2441 / 736,015
1 Please complete the table and calculate the rates of breast cancer for both groups and also for the total population per 10,000 person-years at risk. (4 marks)
2 Please calculate the rate ratio (relative risk) of breast cancer associated with working night shift. (2 marks)
3 What is the interpretation of this result? (2 marks)
4 Calculate the proportion of breast cancer cases that can be attributed to working night shift at least 3 nights per week? How would you interpret this? (3 marks)
5 What study design was used? (1 mark)
6 Was this study design appropriate for this question? Why? (5 marks)
7 How else could this study question be answered with a different study design? Please explain. (5 marks)
Question 2. Please read the following abstract and answer the following questions (25 marks)
Alcohol impairment of drivers is considered the most important contributing cause of car crash injuries. The burden of injury attributable to drinking drivers has been estimated only indirectly. A population-based case–control study examining the relationship between alcohol impairment and drivers was conducted in Auckland, New Zealand between April 1998 and July 1999. Cases were 571 car drivers involved in crashes in which at least 1 occupant was admitted to the hospital or killed. Control subjects were 588 car drivers recruited on public roads, representative of driving in the region during the study period. Participants completed a structured interview asking about their drinking behaviour in the 6 hours prior to the interview and had blood or breath alcohol measurements taken. (Adapted from Connor J. et al., 2004.)
1 What was the study design used? (1 mark)
2 List two advantages and two disadvantages of this study design? (4 marks)
3 Was this study design appropriate for the question asked? Why? (5 marks)
During their interview, drivers completed the 10 questions of the Alcohol Use Disorders Identification Test (AUDIT). The AUDIT is designed to identify drinking patterns that are hazardous or harmful to health. A composite score (out of 40) is derived from the test, with a score of 8 or more considered to represent a hazardous pattern of drinking.
Below is part of the results presented from this study.
Table 1. Distribution of measures of alcohol consumption for crash drivers (cases) and general population drivers (control subjects)
Cases(n=571) / Control Subjects *
(n=588)
No. / (%) / No. / (%)
AUDIT score
0-7 / 407 / 72 / 470 / 82
8-15 / 115 / 20 / 104 / 16
16-23 / 32 / 6 / 13 / 2
24-31 / 8 / 1 / 1 / <1
32-40 / 1 / <1 / 0
*proportions of control subjects are adjusted for sampling design. Column totals could differ as a result of missing data.
AUDIT, Alcohol Use Disorders Identification Test ( A score of 8 or more represents a hazardous pattern of drinking)
1 Using the above information and results please complete the following table (2 marks)
Hazardous Drinking Pattern / Non-Hazardous drinking pattern / TOTALCase
Control
TOTAL / 1151
2 Using the completed table please calculate the odds ratio for engaging in a hazardous pattern of drinking if a person had a car accident. (2 marks)
3 How would you interpret this odds ratio? (2 marks)
4 How else could this study question be answered with a different study design? Please explain. (5 marks)
5 List two advantages and two disadvantages of the study design you chose? (4 marks)
PART B
Please read abstracts 1 and 2 and answer the following questions (12 marks each abstract)
1 What is the study question? (1 mark)
2 What is the study design? (1 mark)
3 Is the study design appropriate for this question? Why? (5 marks)
4 How could this study question be answered with another study design? (5 marks)
Abstract 1
Lloyd, A.R., Wakefield, D., Boughton, C.R., Dwyer, J.M. (1989)
“Immunological abnormalities in the chronic fatigue syndrome”.
Med J Aust, 151, pp.122-124.
The chronic fatigue syndrome is a disorder of unknown aetiology which is characterised by debilitating fatigue. Recent evidence has suggested that viruses may persist in the tissues of patients with chronic fatigue syndrome. A concurrent immunological disturbance is likely to be associated with the persistence of viral antigens. Therefore, the humoral and cellular immunity of 100 patients who were suffering from chronic fatigue syndrome and that of 100 healthy, age-and sex-matched control subjects were compared. This study documents the frequent occurrence of abnormalities within the cellular and humoral immune systems of patients with well-defined chronic fatigue syndrome. Disordered immunity may be central to the pathogenesis of chronic fatigue syndrome. In patients with chronic fatigue syndrome, a significant (P less than 0.01) reduction was found in the absolute number of peripheral blood lymphocytes in the total T-cell (CD2), the helper/inducer T-cell (CD4) and the suppressor/cytotoxic T-cell (CD8) subsets. A significant (P less than 0.001) reduction also was found in T-cell function, which was measured: in vivo by delayed-type hypersensitivity skin-testing (reduced responses were recorded in 50 [88%] of 57 patients); and in vitro by phytohaemagglutinin stimulation. Reduced immunoglobulin (Ig) levels were common (56% of patients), with the levels of serum IgG3-and IgG1-subclasses particularly (P less than 0.05) affected.
Abstract 2
Esparza, M.L., Sasaki, S., Kesteloot, H. (1995) “Nutrition, latitude and multiple sclerosis mortality”.Am J Epidemiol, 142, pp.733-7.
An epidemiologic study has been performed on the relation between the mortality rates from multiple sclerosis for the period 1983-1989 obtained for 36 countries, with dietary fat and latitude. By stepwise multiple regression analysis, saturated fatty acids, animal fat, animal minus fish fat, and latitude correlated independently and positively with multiple sclerosis mortality (p < 0.01-0.001 for fat consumption, and p < 0.05-0.01 for latitude). The ratio of polyunsaturated fatty acids to saturated fatty acids (P/S ratio) and the ratio of unsaturated fatty acids (monounsaturated and polyunsaturated fatty acids) to saturated fatty acids (U/S ratio) correlated independently and negatively with multiple sclerosis mortality (p < 0.05-0.001). These findings support the hypothesis linking dietary fat intake and latitude to multiple sclerosis mortality.
B. Please read abstracts 1 and 2 answer the following questions (16 marks each abstract)
1 What is the study question? (1 mark)
2 What was the main finding? (1 mark)
3 How many subjects were used? (1 mark)
4 Were controls used? (1 mark)
5 Was a placebo used? (1 mark)
6 Was treatment randomised? (2 marks)
7 Were the subjects blinded to the treatment they were receiving? (2 marks)
8 Were the assessors blinded to the treatment the subjects were receiving? (2 marks)
9 What ethical issues arise in this study? (2 marks)
10 Do you think that this is a convincing study? Why? (3 marks)
Abstract 1
Peltola, H., Kayhty, H., Sivonen, A., Makela, H. (1977) “Haemophilusinfluenzae type b capsular polysaccharide vaccine in children: a double-blind field study of 100,000 vaccines 3 months to 5 years of age in Finland”. Pediatrics, November,60(5), pp.730-737.
A recently developed Haemophilusinfluenzae type b capsular polysaccharide vaccine was given to 48,977 children 3 months to 5 years of age; an equal number of children receiving group A meningococcal vaccine served as controls. The protection as well as serum antibody response was strongly age-dependent. Among children who had received the H. influenzae type b vaccine when 18 months of age or older, there were no cases of bacteremic disease caused by H. influenzae type b in the first year after vaccination. At the same time 11 such cases were seen in the control group of the same age, a highly significant difference. In the second year after vaccination two cases occurred in the H. influenzae type b-vaccinated group, five in the meningococcal-group A vaccinated group. No protection was seen among children who had been younger than 18 months when vaccinated, even if they received a booster dose of the vaccine. The serum antibody response to the H. influenzae type b polysaccharide, measured by radioimmunoassay, was poor in children below 18 months of age and good in those above it. No effect of the vaccine could be seen on the nasopharyngeal carriage of
H. influenzae type b, which was approximately 6% in this age group. Adverse effects of the vaccine were mild.
Abstract 2
Edwards, B.C., Zusman, M., Hardcastle, P., Twomey, L., O’Sullivan, P., McLean, N. (1992) “A physical approach to the rehabilitation of patients disabled by chronic low back pain”. Med J Aust, 156(3), pp.167-172.
OBJECTIVE: To report the outcome of a multidisciplinary physically based program to treat sufferers of chronic low back pain who had not responded to previous treatment. DESIGN: Prospective intervention study. SETTING: The treatment program was conducted at the private practice of Brian C Edwards and Associates Rehabilitation Centre. PATIENTS: A total of 54 patients participated in the treatment program. All patients were medically referred. No specific exclusion criteria were used; however, all were not working and had not responded to previous treatment. INTERVENTION: The rehabilitation program consisted of mobilising physiotherapy, isokinetic testing, physical reconditioning, work hardening and psychological testing. This was carried out for seven hours a day, five days a week for four weeks. RESULTS: Of the 54 patients taking part in this trial 30 (55%) were successfully rehabilitated (returned to work) and remained so at a follow-up session one year later. CONCLUSION: While selection criteria for successful rehabilitation have not been established, the results do indicate that such physical rehabilitation programs have an important part to play in the rehabilitation of sufferers of chronic low back pain.