Incorporation Of Antioxidants For Reduction Of Cancer Risk: A Cohort Study Among US Middle-Aged Men

1. What were the exposures and the outcomes studied?
2. How did the authors define the reference exposure categories (i.e., the ‘unexposed’) for the three dietary variables considered?
3. Was this an incidence or a prevalence study? (State your choice) Explain.
4. Was this an historical/retrospective or a concurrent/prospective study? Explain.
5. Was the cohort under investigation fixed or dynamic? (State your choice) Explain.
6. (a) What was the relative risk (not incidence rate) of death from all causes, comparing the highest tertile of vitamin C exposure among smokers to the lowest tertile?
6. (b) What was the risk difference?
7. What was the cancer mortality rate ratio for smokers, compared to non-smokers?
8. What were the odds of coronary heart disease death in all men in the lowest β-carotene (not vitamin C) tertile?
9. (a) What was the odds ratio of cancer death in smoking men in the middle β-carotene tertile relative to the lowest tertile?
9. (b) What was the corresponding relative risk?
9. (c) Compare the two.
10. What was the cancer mortality rate difference in all smoking men in the highest composite index tertile, relative to the middle tertile?
11. What were the odds of being a current smoker at entry in this cohort?
12. What was the general result of this study?

Questions 13 to 15 are based on the paper: Sytkowski et al. Sex and time trends in cardiovascular disease incidence and mortality: the Framingham heart study, 1950-1989.

13. Using the data from “Materials and Methods” and from Table 3, estimate:

a) The 10-year crude risk of cardiovascular disease in women in the 1950 cohort
b) The 20-year crude risk of stroke death in men in the 1960 cohort 14. Table 4 indicates that in the 1950 cohort, the frequency of diabetes at 10 years in women was 5.7%.
a) Does this represent an estimate of risk or of prevalence? (State your choice)
b) Explain.
15. The footnote to table 3 indicates that in men from the 1950 cohort, sample sizes were 618 at baseline and 510 after 10 years. On the basis of this information, provide:
a) A rough estimate of the number of person-years accumulated during this 10-year follow-up
b) Then estimate the 10-year stroke mortality rate in these men.

Answer 1:

In the given paper the author have hypothesized that incorporation of antioxidants like vitamin C and beta carotene would be helpful in the reduction of cancers through the inhibition of carcinogenic compounds like nitrosamines, superoxide.  Thus the differences between the intakes of the nutrients have been measured through their effect on mortality (Bjlakovic, Nikolva and Gluud 2014).

The outcomes of the study have been received in accordance with the hypothesis. There is a negative correlation between the consumption of food rich in antioxidants and the risk of cancers (Boland et al. 2015). The present study has tried to estimate the differences in the intake of Vit C and Beta carotene as well as both on the average deaths of people through a cohort study. The studies have been conducted among middle aged men in US.

Answer 2:

The relation between the unexposed individuals, people not affected with cancer in this case have been compared with variable like VitC, β Carotene and both. Thus mortality rates have been statistically determined and examined for establishing the relation between the various variables and the subsequent risk of developing cancer.

Answer 3:

The given paper is a prevalence study. A prevalence study is a kind of observational study which involves analysis of data from the particular population along with a representative subset especially at a specific point of time (Oh et al. 2016). In this paper, the association bet Vit C and β carotene uptakes have been assessed among a population of middle aged men within a cohort study between 1958, 1959. Thus, the prevalence of risks due to cancer has been studied.

Answer 4:

Here a prospective study has been conducted as it has considered the outcomes of the experiment involving the development of the diseases during a particular study period which relates to factors like suspended risks. Here the risk of death has been considered.

Answer 5:

This study has been an open one as the participants of the particular company, Western Electric Study has been selected. Thus the population of the workers in the company is dynamic as the people might change the company and the required population might not be specific. Thus, individuals contributing to the cohort study might not be followed through time (Hwang et al. 2014).

Answer 6:

1. For men inclusive of smokers as well as non-smokers, the risks of Vit C  has been inversely associated with cancer (risks of 1.00, 0.82, 0.61). However the risks from all causes have not been able to show a clear relationship between death and coronary diseases. 95 % of confidence level has been received from the difference of the highest and lowest tertiles.
2. The relative risks of 1.00, 1.03, 0.75 have been found as the differences between the highest and lowest tertiles.

Answer 7:

The subsequent intakes of Vitamin C and Beta carotene between smokers and non-smokers have not produced significant results. A mortality ratio of 0.58 has been found for dietary intakes of 50 mg/day of antioxidants but the difference with respect to smokers and non-smokers have not been explained.

Methodology

Answer 8:

The odds have been 0.79 (0.60-1.04) for deaths from coronary diseases. The odds of the death due to beta carotene with an increased intake of 3mg/day of vitamin C is 0.78 (0.58-1.03) die to deaths from coronary diseases. These results have been after 5 years of follow up. Overall there has been a 95% probability of cancer.

Answer 9:

36. The odd of the smoker having beta carotene has been 28 with respect to the lowest tertile of beta carotene which is 36. Thus the odd ratio among smokers in the beta carotene table is 28/36.
37. The relative risk is 0.66 against 0.73.
38. Thus it can be seen that the relative risk for the deaths among smokers have been 0.66 with deaths of 28 and there has been risk of 0.73 against 36 death which is much higher than the earlier values.

Answer 10:

In the chart of vitamin C the difference between the mortality rates among smoker suffering from cancer is 34-28 for deaths and 0.82-0.52 for the relative risks. For the chart of beta carotene the number of deaths has been 28 compared to 6 and the risks has been 0.66 than 0.73.

Answer 11.

The odds of being a current smoker among all causes are 0.63. The odds here is considered as the probability for acquiring the diseases.

Answer 12.

The general result of the study has been a reduction in the relative risks of cancer with an increased dose of antioxidants like vitamin C and Beta carotene per day (Valdez-Ramos et al. 2015). It can be done through the incorporation of two oranges for Vit C and two carrots in the diet. For a 31 % lower risk of deaths from cancer.

Answer 13

1. a) The riskamong women in the 1950 cohort has been 372 during the incidence and it has been 147 during the mortality. Thus there has been a reduction in the number of cases identified with the disease and those who died from the disease.
2. b) The distribution of cases in men among the 1960 cohort   suffering from stroke has been 30 over the 20 years and the number of cases reported has been 14.

Answer 14

1. a) It represents prevalence.
2. b) The number of people affected by diseases for the first time is indicated as prevalence. Thus, the percentage of new incidences of the disease is very low (5.7%) which is indicative of prevalence.

Answer 15

5100. Rough estimate of the number of person years for the first case is 6180 and the second case is 5100.
5101. The stroke mortality risks of these men in 1950 cohort is 9.

References

Bjelakovic, G., Nikolova, D. and Gluud, C., 2014. Antioxidant supplements and mortality. Current Opinion in Clinical Nutrition & Metabolic Care, 17(1), pp.40-44.

Bolland, M.J., Grey, A., Gamble, G.D. and Reid, I.R., 2014. The effect of vitamin D supplementation on skeletal, vascular, or cancer outcomes: a trial sequential meta-analysis. The lancet Diabetes & endocrinology, 2(4), pp.307-320.

Hwang, A.C., Peng, L.N., Wen, Y.W., Tsai, Y.W., Chang, L.C., Chiou, S.T. and Chen, L.K., 2014. Predicting all-cause and cause-specific mortality by static and dynamic measurements of allostatic load: a 10-year population-based cohort study in Taiwan. Journal of the American Medical Directors Association, 15(7), pp.490-496.

Oh, C.M., Won, Y.J., Jung, K.W., Kong, H.J., Cho, H., Lee, J.K., Lee, D.H. and Lee, K.H., 2016. Cancer statistics in Korea: incidence, mortality, survival, and prevalence in 2013. Cancer research and treatment: official journal of Korean Cancer Association, 48(2), p.436.

Pandey, D.K., Shekelle, R., Selwyn, B.J., Tangney, C. and Stamler, J., 1995. Dietary vitamin C and β-carotene and risk of death in middle-aged men: the Western Electric study. American journal of epidemiology, 142(12), pp.1269-1278.

Sytkowski, P.A., D'Agostino, R.B., Belanger, A. and Kannel, W.B., 1996. Sex and time trends in cardiovascular disease incidence and mortality: the Framingham Heart Study, 1950–1989. American journal of epidemiology, 143(4), pp.338-350.

Valdés-Ramos, R., Ana Laura, G.L., Beatriz Elina, M.C. and Alejandra Donaji, B.A., 2015. Vitamins and type 2 diabetes mellitus. Endocrine, Metabolic & Immune Disorders-Drug Targets (Formerly Current Drug Targets-Immune, Endocrine & Metabolic Disorders), 15(1), pp.54-63.