1.The incidence of heart disease in Australian males is ~ 3% per year; those of Indian Asian origin have rates as much as 40% higher. To address this, one study recruited 258 Indian Asians with heart disease from cardiology outpatient departments, coronary care units and coronary angiography records of 3 New South Wales hospitals. 518 Indian Asians with no heart disease were identified at random from the age-sex register of 56 local general practitioners. Samples for plasma homocysteine were taken in fasting state, i.e., before breakfast. Homocysteine levels were related to heart disease.

a) What kind of study is this? (1 mark)

Homocysteine level (umol/L)	Heart disease	No heart disease
>15	156	288
11-15	78	166
<11	24	64

1. b) Calculate the odds ratio for each level of homocysteine (11-15 and >15) compared to the lowest level (<11), and interpret what these ORs mean. (2 marks)
2. c) Assuming that these results are correct, what percentage of heart disease in the entire population of Indian Asians could be avoided by treating high homocysteine levels, i.e., >15 umol/L? (Ignore the 11-15 umol/L stratum for this question). State the name of this measure, and the assumptions needed to calculate it, and state whether these assumptions are acceptable in this example. (2 marks).
3. d) Name 2 biases that could influence the results during recruitment, and 2 biases that could influence results after recruitment in this study. (1 + 1 = 2 marks)
4. The authors go on to describe a randomized controlled trial, where 158 Indian Asians with a family history of heart disease and high homocysteine levels are randomised to receive either 5 mg folate and 250 mg vitamin B6 daily (n=78) or placebo (n=80). These treatments are thought to lower homocysteine levels, and hence the incidence of heart disease. Instead of waiting many years for the development of clinical heart disease, they use ultrasound of the common femoral artery at 24 months as a surrogate marker of atherosclerosis.

The results are given below:

Abnormal ultrasound of femoral artery	Treatment group	Placebo group
Baseline	0/78	0/80
2 years	3/78	4/80

1. a) State and explain the absolute risk reduction with folate and B6 vs. placebo? (2 marks)
2. b) What is the relative risk reduction? (2 mark)
3. c) What is the number needed to treat? (2 mark).

3.Fat consumption and sedentary life style both contribute causally to the occurrence of coronary heart disease. These risk factors are not independent; in fact they operate synergistically. A study of fat consumption in relation to coronary heart disease that fails to stratify or otherwise control for level of sedentary life style would be guilty of which of the following threats to validity:                                         (2 mark)

1. Ascertainment bias

1. Observer bias

1. Confounder

1. None of the above

Do you want your assignment written by the best essay experts? Then look no further. Our teams of experienced writers are on standby to deliver to you a quality written paper as per your specified instructions. Order now, and enjoy an amazing discount!!