HEP 444: Epidemiology

Dr. Adams

9/29/2022

HEP 444 Cohort Study

Questions

1. What is at least one characteristic of this study qualifying it as a cohort study design?

Subjects are followed up over an extended period of time in this case the Japanese males

2. What is the hypothesis tested in this study?

the relationship between maintaining a healthy CRF level over a period of time and a future increase in T2DM risk in Japanese men.

3. Why did the authors stratify the participants into the fit and unfit categories?

To classify the participants in regard to AUC ratio, such that Participants with an AUCratio of 100 or above were classified as FitAUC, whereas those with a lower AUCratio were classified as UnfitAUC

4. Why did authors measure the subject’s characteristics in this study?

Such that area under the curve (AUC) and reference area (AUCref) could be calculated for each person throughout the 8-year measurement period (April 1979–March 1987) to estimate integrated CRF level and guideline for fit reference values, respectively.

5. List two characteristics that are higher in the unfit group compared to the fit group.

• the multivariable adjusted HR of T2DM

• the cumulative incidence of T2DM

6. What is the purpose of showing age-adjusted HR and multivariate-adjusted HR?

To show how cardiorespiratory fitness is affected based on individuals’ measurements

7. For the multivariate HR, what was the percent increase in risk for developing diabetes in the unfit group compared with the fit group?

((1.33 – 1.00)/1.00) × 100 = 33%

8. Which of Hill’s five criteria for causality does the HR and 95% CI for the unfit group satisfy?

specificity (casual factor pertains exclusively to the result in issue)

9. Which of the two groups developed more cases of diabetes?

The UnfitAUC group

10. In which of the 5-year intervals did the cases of diabetes begin to differ?

At 23 the number of participants at risk of getting diabetes in the FitAUC group were more compared to that those of UnfitAUC group

11. In which age group did the HR for the unfit status show strength of association?

Age 40–59 years

12. For the group identified in #11, what was the percent increase in the risk of developing diabetes in the unfit as compared with the fit group?

((112-53)/112) ×100 = 53 %

13. Compared to the staying fit at both periods (1979, 1986), which of the three-fitness combination(s) showed a statistically increased risk of developing diabetes?

Unfit initial × UnfitAUC the number of cases increased from 84 to 220

14. How did the authors address consistency of results?

It has been shown in several earlier research that a lower CRF level is linked to a greater risk of T2DM. Additionally, among Japanese men, this link has been verified. Another study revealed a negative connection between physical performance in college and later risk of T2DM. In accordance with these results, the research demonstrated that, compared with those with an unfit CRF level according to the “Physical Activity Reference for Health Promotion 2013” in Japan at baseline, Japanese guys with a fit CRF level had a decreased risk of T2DM

15. How did the authors suggest biological plausibility?

Exercising when pregnant has been shown to improve insulin sensitivity and glucose homeostasis in children. The findings of such studies lend credence to the hypothesis that epigenetic modification is a plausible mechanism underlying the association between maintaining a healthy CRF level for a number of years and a reduced risk of developing type 2 diabetes in subsequent years.

16. Explain why the study did not show a dose response relationship.

Achieving the level of fitness in CRF recommended by the Japanese guideline reduces the risk of developing type 2 diabetes. In this case there is no dose-response relation this is because increasing the amount of exposure cannot increase the risk of getting diabetes.

17. How did the study show temporal relation?

This research followed a group of Japanese males for many years after they had achieved a healthy CRF (as defined by the Ministry of Health, Labor, and Welfare). This means exposure preceded the outcome

18. What statistical procedure did the authors use to show strength of association in the results?

Although the Unfitinitial FitAUC group had a greater chance of developing type 2 diabetes than the Fitinitial FitAUC group, the difference in their hazard ratios was not statistically significant. This data indicates that the potential disadvantage of an initial unfit CRF level that led to the development of T2DM may have been mitigated by the achievement of a fit CRF level as advised by the Japanese guideline after the first CRF measurement.

19. Why are you unable to generalize the results of this study to obese men?

Since there were only a small number of obese participants in the study population (those with a BMI of 30 at baseline accounted for only 1% of the population), the findings of this study may only be applicable to populations with weights that are relatively normal.

20. What advice would you give to a male 21-59 to reduce risk of diabetes years based on the results of this study?

Encourage patients with an unsuitable CRF level to engage in physical exercise for the prevention of type 2 diabetes by pointing out the benefits of doing so.