Introduction to Epidemiology (401076)

This assignment is based on the learning objectives and concepts in Topic 1. There are a total of 54 marks and this assignment will contribute 20% towards the total assessment for this subject.

Your assignment should be typed in this document! leave adequate space between questions.

Leave the question as is – don’t erase it from the document.

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Be as brief as possible in your answers. No answers need to be longer than a few short sentences or short paragraphs.

No references are needed!

Make sure the way you reached the final answer is clearly detailed! Even if you provided the correct final answer you will not get the full mark unless the way you reached it is specified.

Question 1:

In 2006, a group of 2,200 men and women aged 20 years were recruited from the general population and assessed for Herpes Simplex Virus – Type 2 (HSV-2). 144 participants were found to have HSV-2 when tested at baseline. Participants who did not test positive for HSV-2 in 2006 were followed-up and assessed again after 4 years of follow-up (only those who previously had tested negative for HSV-2 were tested again at follow-up). A further 51 cases of HSV-2 were identified during this 4 year period, either diagnosed during the interim or diagnosed during the study assessment. (It is assumed that once participants contract HSV-2 they remain HSV-2 positive.)

(a) What was the prevalence of HSV-2 among study participants in 2006? [2 Marks]

(b) What was the prevalence of HSV-2 among study participants after 4 years of follow-up? Assume no loss to follow-up. [2 marks]

 (c) What was the cumulative incidence of HSV-2 among study participants over the study period? [4 marks]

 (d) Calculate the total number of person-years at risk during the 4 year period. (Assume that HSV-2 was acquired randomly during the 4 year period. That is, those who acquired HSV-2 were at risk for half the time of those who did not acquire HSV-2). [4 marks]

(e) What was the incident rate of HSV-2 among participants for the 4 years. [4 marks]

 (f) Assuming that the incidence rate of HSV-2 remains constant, what should happen to the prevalence of HSV-2 in this cohort over time? [2 marks]

 Question 2:

Calculate the rates specified below (a to c), using the following information about the black population of the United States 1n 1994 (numbers were modified to simplify calculations and not all points are relevant to the questions asked here)

• Average population size 28 million, including 7.2 million women aged 15-44.
• Live births: 600,000
• Fetal deaths: 4380
• Death in the first week of life: 6120
• Death in the first 28 days of life (excluded first week): 960
• Death in the first year of life (excluding in the first 28 days): 3900
• Total deaths in the population: 230,000
• Deaths from heart diseases: 75,000

(a) What is the crude birth rate?  [2 Marks]

 (b) What is the infant mortality rate?  [2 marks]

(c) What is the crude mortality rate? [2 marks]

Question 3:

Question 3 relates to the following table of male suicide in the Sydney metropolitan area, stratified by quintile of socio-economic status (SES). (Only the lowest and highest SES groups are shown). Note: 5 years of death data are presented. Population data comes from a single census year (2011). It is conventional to present mortality rates as annual average rates.

	Lowest SES quintile, Suicides	Lowest SES quintile, Population	Highest SES quintile, Suicides	Highest SES quintile, Population	Total suicide (All quintiles)	Total population (All quintiles)
	2009-2013	2011	2009-2013	2011	2009-2013	2011
Males
15-24	195	123,961	116	140,942	779	667,548
25-34	242	134,303	158	134,595	1,044	693,988
35-44	204	133,242	123	135,819	865	688,839
45-54	147	110,680	92	124,576	594	577,128
55-64	89	83,943	55	75,308	364	381,248
65-74	76	73,509	42	56,097	283	304,226
75+	56	39,197	43	36,293	224	172,856
	1,009	698,835	629	703,630	4,153	3,485,833

(a) Calculate the crude suicide incidence rate (per 100,000) for the lowest SES quintile and the highest SES quintile for those aged ≥15 years and summarise your findings[4 marks]

(b) Calculate the direct age-standardised suicide incidence rate (per 100,000) for the lowest SES quintile using the highest SES quintile as the standard. [4 marks]

(c) Do you think that age structure is an important factor in explaining the differences in suicide between low and high SES groups? Using the age-specific data you calculated, make a specific comment about the difference between the crude suicide rate and the direct age-standardised suicide rate. [4 marks]

Question 4:

A study was conducted to explore the relationship between dietary anti-oxidant intake (Vitamin A and Vitamin E) and the risk of having colon cancer. 120,000 people, aged 20-70 years, were selected at random from the total population living in Melbourne in 1987 and invited to join the study. 110,700 of those invited agreed to participate. Participants were interviewed about their dietary intake using food frequency questionnaire so researchers can calculate the amount of anti-oxidant in the diet. Other health risk factors such as smoking, exercise and stress and demographics were also asked at start. Every two years thereafter participants were contacted and asked the same questionnaire. At the end of the study, 10 years later, study researchers were still in contact with 64% of the study population. Outcome data (cancer episode and site) were available for 97% of the original study population from the Victorian Cancer Registry. The study found that the risk of cancer was 2% lower among people with a higher intake of anti-oxidant vitamins, compared to those with lower intakes

 What study design it is [2 marks]

 What are the key points that led you to think that this is the design [2 marks]

What study design would be more efficient in terms of time and cost for asking the same research question? Explain no more than 100 words [2 marks]

 Question 5:

“Investigators wishes to know if eating dark chocolate is associated with better cholesterol level in the  blood among middle -aged people 45-65 years)”

1. ‘Propose an epidemiological study design to explore this question and justify why you chose this design? ‘[4 Marks]
2. ‘Assuming you are one of the investigators – please provide a short description about the participants in the study, what data you will need to collect to answer your research question and at which time point you collect this data’  [4 Marks]
3. What other study design you can consider for this research question and explain why you chose it [4 Marks]