A cohort study was undertaken to examine the association between high lipid leve

Question

A cohort study was undertaken to examine the association between high lipid level and coronary heart disease (CHD). Participants were classified as having either a high lipid level (exposed) or a low or normal lipid level (unexposed). Because age is associated with both lipid level and risk of heart disease, age was considered a potential confounder or effect modifier and the age of each subject was recorded. The following data describes the study participants: Overall, there were 11,000 young participants and 9,000 old participants. Of the 4,000 young participants with high lipid levels, 20 of them developed CHD. Of the 6,000 old participants with high lipid levels, 200 of them developed CHD. In the unexposed, 18 young and 65 old participants developed CHD. Construct age stratum specific two by two tables and then perform a chi-square test to see if effect measure modification is present

Explanation / Answer

For the Young Group

Ouput :

Chi-Square Test for Association: C1, Worksheet columns

Rows: C1 Columns: Worksheet columns

Developed Not
CHD developed All

High lipid level 20 3880 3900
13.7 3886.3

Low lipid level 18 6882 6900
24.3 6875.7

All 38 10762 10800

Cell Contents: Count
Expected count

Pearson Chi-Square = 4.511, DF = 1, P-Value = 0.034

Likelihood Ratio Chi-Square = 4.314, DF = 1, P-Value = 0.038

Interpretation:Since P-value (0.034) of the test is less than the l.o.s(0.05) we can say that among Young group there is significant association beteween lipid level and development of CHD

Analysis among Old Group

Output

Rows: C1 Columns: Worksheet columns

Developed Not
CHD_1 developed_1 All

High lipid level 200 5800 6000
176.7 5823.3

Low lipid level 65 2935 3000
88.3 2911.7

All 265 8735 9000

Cell Contents: Count
Expected count

Pearson Chi-Square = 9.526, DF = 1, P-Value = 0.002
Likelihood Ratio Chi-Square = 10.026, DF = 1, P-Value = 0.002

Interpretation :Since P-value (0.002) of the test is less than the l.o.s(0.05) we can say that among old group there is significant association beteween lipid level and development of CHD

Developed CHD Not developed
CHD Total High lipid level 20 3880 4000 Low lipid level 18   6882 7000 38 10762 11000

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