Essay: Study Designs In Public Health

Cross-sectional study

a.Cross-sectional study

b.Randomised controlled trial

c.Ecological study

d.Prospective cohort study

e.Quasi-experimental study

f.Retrospective cohort study

g.Case-control study

2.A paper-based survey form was posted to 6,000 Australian adults aged between 18 and 69 years whose addresses were randomly selected from the electoral roll. They were asked about their usual diet, physical activity and stress levels.

a.Cross-sectional study

b.Ecological study

c.Prospective cohort study

d.Retrospective cohort study

e.Case-control study

f.Randomised controlled trial

g.Quasi-experimental study

3 A history of dietary salt (sodium) consumption was obtained from all patients entering a hospital who have stomach cancer and compared with salt consumption histories of patients with appendicitis who enter the same hospital.

a.Cross-sectional study

b.Ecological study

c.Prospective cohort study

d.Retrospective cohort study

e.Case-control study

f.Cluster-randomised trial

g.Randomised controlled trial

4.In 2015, an investigator performed a computerised search of records for the 40 community dental clinics across metropolitan Melbourne to identify children who had attended the dental service between 2000 and 2005. From these records he identified children who had fluoride varnish applied to their teeth and a comparable group not treated with fluoride varnish. After obtaining ethics approval, the children, were invited to attend for free dental examinations to detect any evidence of tooth decay.

a.Cross-sectional study

b.Cluster-randomised trial

c.Ecological study

d.Prospective cohort study

e.Retrospective cohort study

f.Case-control study

g.Randomised controlled trial

5.What type of study is presented in this graph?

a.Ecological study

b.Prospective cohort study

c.Retrospective cohort study

d.Cluster-randomised trial

e.Case-control study

f.Cross-sectional study

g.Randomised controlled trial

6.Investigators at a major paediatric hospital in Australia were interested in the impact of family breakdown during early childhood on the development of mental health problems in adolescents.  They recruited 5,000 children in grade 1 (and their parents) from 100 primary schools in regional Victoria and followed them annually for the next ten years.  They asked questions about family structure and living arrangements (including separation and divorce of the parents) and conducted screening test for anxiety and depression among the children at each follow-up.

a.Randomised controlled trial

b.Cross-sectional study

c.Quasi-experimental study

d.Ecological study

e.Retrospective cohort study

f.Prospective cohort study

g.Case-control study

7.A longitudinal study was conducted with a sample of 11,500 women from culturally diverse backgrounds aged 30 to 69 years. Of these women, 2170 reported that they had diabetes at the start of the study. The measure you could calculate from the information provided is: (1 mark)

a.Cumulative incidence

b.Incidence rate

c.Prevalence rate ratio

d.Point prevalence

e.Period prevalence

f.Attributable fraction

g.None of the above

8.A study that aimed to assess hip fractures recruited 16,230 South Korean men aged 50-69 years. The study found 849 men reported a hip fracture over the next five years.  The measure you could calculate from the information provided is: (1 mark)

a.Point prevalence

b.Period prevalence

c.Cumulative incidence

d.Incidence rate

e.Prevalence rate ratio

f.Attributable fraction

g.None of the above

9.Which of the following is a disadvantage of cohort studies? (1 mark)

a.Not s.uited for the study of common diseases because only small numbers of subjects would be required.

b.Maintaining high rates of follow-up can be difficult.

c.Not suited when the time between exposure and disease manifestation is short, as this would reduce the follow-up time required.

d.Only allow a single exposure and outcome to be studied

e.None of the above

10.Which of the following features should apply to a screening program (1 mark)

a.It should be commenced before there is an identified health issue in the population

b.There should be a low prevalence of pre-clinical (early stage) disease

c.We don’t need to understand the natural history of the disease as screening will allow us to study this in detail

d.The disease should be severe, relatively common and perceived as a public health problem

e.There should be a low prevalence of severe, untreatable disease at a late stage

f.The test available should identify at least 50% of the cases

11.The advantages of Case Control studies are? (1 mark)

a.Relatively quick and cheap to conduct

b.Can investigate a wide range of possible risk factors

c.Can be used to efficiently identify and study cases of rare outcomes

d.Can employ expensive or time?consuming tests

e.Both a and b

f.All of the above

g.None of the above

Ecological study

Cross-sectional study

Retrospective cohort study

Cross-sectional study

Prospective cohort study

Period prevalence

Maintaining high rates of follow up can be difficult

The disease should be severe, relatively common and perceived as a public health problem

Relatively quick and cheap to conduct

Can investigate a wide range of possible risk factors

Can be used to effectively identify and study cases of rare outcomes

Can employ expensive or time-consuming tests

Occurs clearly in excess of the expected numbers

They are quick, cheap and easy to do with existing data

They are useful for generating hypotheses for later testing

The gender of the study participants

The household annual income of the study participants

Odds ratio

True

The results should be treated with caution as it could be due to chance variability in the data. This is because it has an odds ratio of 0.86 with a 95% CI of 0.61-1.26. This means that the true odds ratio of the target population lies between 0.61-1.26. Therefore, the true population odds ratio has a possibility of being 1.0. Odd ratio is one if the measure of association between the cases and the control in case control study or exposure and the outcome in the cohort study. Odds ratio also measures the strength of association between the exposure and the outcome. It is calculated by taking the odds of the disease in the exposed group divided by the odds of the disease in the unexposed group.

Odds ratio, OR =

Interpretation: An odds ratio of 1 is interpreted as there being no increased or decreased likelihood of a factor (living in rural area) affecting an outcome (daily smoking). Living in rural is not associated with more daily smoking. An odds ratio of more than 1 means there is an increased likelihood of the outcome occurring due to the factor in question while an odds ratio of less than 1 means there is a decreased likelihood of the outcome occurring due to the factor in question. It should be noted that Odds ratio does not totally establish that the exposure is the contributing factor to the outcome. It could be that the association is due to a third factor that was not checked in the study. These factors that are related to both the exposure and outcome are known as confounding factors.

Airborne diseases like influenza flu. This is because the games will bring together a lot of people together within relatively enclosed spaces. This is a conducive environment for the transmission of airborne diseases. Some flu strains are also known to be very contagious. Some of the flu can also be fatal. This means they pose a big threat and are therefore a major public health concern.

Randomized controlled trial

Sexually transmitted infections. The common wealth games gives an opportunity for a large number of people to meet at a single place. This opportunity would increase the level of sexual activity and incidences of sexually transmitted infections. The games might also be an avenue of spread of new, more drug resistant strain of sexually transmitted infections.

The health surveillance system was not designed in the best way. They should have collected more data. A better way was to start the data collection before the arrival of the teams. This would have enabled collection of data on determinants of health that would have influenced the health of the teams and were in place before the teams arrived. These factors include the level of sanitation, water supply and food sanitation and safety, accommodation and any pre-existing diseases among others.

Data collection should also continue past the final day. This is because some diseases have a longer incubation period. This means that the clinical symptoms of the disease will manifest several hours or days after the exposure. Such disease includes most of the sexually transmitted infections. These diseases might be missed if data collection is stopped on the final day of the games.

Loss to follow up

The analysis compared people who were randomised to the aspirin group with those who were not randomised to take aspirin, regardless of whether or not they actually took the aspirin.

Controls who are also hospital patients may be more representative of hospitalised cases than controls selected from general population

Odds Ratio. This is the odds of the disease in the exposed divided by the odds of the disease in the unexposed.

OR= odds exposed/odds unexposed

      = 1.419

      = 1.4

The result means that heavy alcohol drinkers have 1.4 times more likelihood of developing pancreatic cancer compared to the non-heavy alcohol drinkers. An odds ratio of 1 signifies that the exposure in this case heavy drinking has no association with the outcome. An odds ratio of more than 1 signifies that the exposure increases the risk of having the outcome by a fold represented by the value of the odds ratio. An odds ratio of less than 1 signifies that the exposure reduces the risk of having the outcome in question. It means that the exposure is instead protective against the outcome in question. However, the odds ratio does not totally establish the association between the exposure and the outcome as there might be other confounding factors.

The exposed and non-exposed groups under study be as similar as possible with regard to possible confounding factors