Introduction to Epidemiology 6th Edition by Ray M Merrill

Exercise 4

From Table 1, which body systems were at the most risk of exposure to chemical leaks? What is the significance of such a determination?

Table 1

Exposure	All Malformations Combined (740–759)	Nervous System (740–742)	Musculoskeletal System (754–756)	Integument System (757)
Exposure Risk Index
No exposure risk	1.00	1.00	1.00	1.00
Low exposure risk	1.09** (1.04–1.15)§	1.27* (1.03–1.57)	1.09 (1.00–1.18)	1.22** (1.08–1.38)
High exposure risk	1.63** (1.34–1.99)	1.48 (0.69–3.16)	1.75** (1.31–2.34)	2.63** (1.90–3.67)
Chemical Leaks
Not exposed	1.00	1.00	1.00	1.00
Exposed, but no leaks found at site	1.08* (1.02–1.15)	1.35* (1.06–1.72)	1.08 (0.98–1.20)	1.22* (1.06–1.40)
Exposed, and leaks found at site	1.17** (1.08–1.27)	1.16 (0.87–1.55)	1.16* (1.03–1.31)	1.38** (1.17–1.62)

* p<0.05; ** p<0.01.

† Adjusted for maternal age, race, education, complications during pregnancy, parity, population density for county of residence, and gender of the child, by logistic regression.

‡ Data from ICD-9, International Classification of Diseases, 9th revision

§ Numbers in parentheses, 95% confidence interval.

Step 1 of 3

Odds Ratio measures the association with, and dependence of an outcome on the exposure to a test material. It is thus a means of quantification of the strength of presence and absence of a test substance on the perceived outcome. It is calculated as the likelihood of occurrence of one condition, when a variable has already been applied to the likelihood of occurrence of the condition when a variable has not been applied.