To examine the association between high blood sugar and glaucoma, a group of 3154 people was observed for a period of 20 years in the NYC metropolitan area. The study participants were middle age epidemiologists working in the tri-state area. Participants received a free physical and nutritional evaluation as well as an eye exam. A total of 1589 people were found to have high blood sugar levels and 1565 had normal blood sugar. The occurrence of glaucoma was evaluated every year. At the end of the study, there were 257 cases of glaucoma among the high blood sugar and 112 cases in the normal blood sugar group.
1. Complete the 2 by 2 table. Please fill in 2x2 table responses for all question marks. This means labeling disease and exposures and filling in the appropriate numbers in the table.
2. Calculate the relative risk.
3. What can be concluded about the relationship between high blood sugar and glaucoma?
4. The above is an example of what study design?
5. Is this study prospective, retrospective, or ambidirectional in its assessment of the outcome?
1. The 2x2 table can be filled out as follows:
| Glaucoma Present | Glaucoma Absent | Total
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High Blood Sugar | 257 | ? | 1589
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Normal Blood Sugar | 112 | ? | 1565
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Total | ? | ? | 3154
To calculate the missing numbers, we can use the information provided. Since the total number of participants is 3154, we can fill in the missing numbers in the table by subtracting the known numbers from the totals:
- For the Glaucoma Absent group in the High Blood Sugar row, we can calculate 1589 - 257 = 1332.
- For the Glaucoma Absent group in the Normal Blood Sugar row, we can calculate 1565 - 112 = 1453.
- For the Total Glaucoma column, we can calculate 257 + 112 = 369.
- For the Total Absent column, we can calculate 1332 + 1453 = 2785.
- For the Total row and column, we can use the known totals: 1589 + 112 = 1701 and 257 + 1332 = 1589.
| Glaucoma Present | Glaucoma Absent | Total
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High Blood Sugar | 257 | 1332 | 1589
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Normal Blood Sugar | 112 | 1453 | 1565
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Total | 369 | 2785 | 3154
2. To calculate the relative risk, we need to divide the risk of glaucoma in the high blood sugar group by the risk of glaucoma in the normal blood sugar group.
Relative Risk = (Number of cases in high blood sugar group / Total number of high blood sugar participants) / (Number of cases in normal blood sugar group / Total number of normal blood sugar participants)
Relative Risk = (257 / 1589) / (112 / 1565)
3. To conclude the relationship between high blood sugar and glaucoma, we can compare the relative risk calculated in step 2 to 1. If the relative risk is greater than 1, it indicates a positive association between high blood sugar and glaucoma. If the relative risk is less than 1, it indicates a negative association. The magnitude of the relative risk can also provide insights into the strength of the association.
4. From the description provided, this study design appears to be a prospective cohort study. Participants were observed over a period of 20 years, and their blood sugar levels and occurrence of glaucoma were evaluated throughout the study period.
5. The study design is prospective in its assessment of the outcome. Participants were followed over time, and the occurrence of glaucoma was evaluated at regular intervals.