PART in a small fictional island nation, a team of epidemiologists has been stud
ID: 3052538 • Letter: P
Question
PART in a small fictional island nation, a team of epidemiologists has been studying the relationship between very low birth weight and risk of cognitive, motor, and behavioral problems. Five years ago these investigators initiated a cohort study. Using birth certificate files and delivery room entry logs, they attempted to identify all full-term births over a 6-month period. The investigators weight babies and a representative sample of normal birth weight babies into their study. The investigators then examined the children administered a standardized developmental screening test to assess personal-social, language, and motor-adaptive skills. Based on this test, the investigators classified the children into two groups: delayed development and normal development. enrolled all low birth every year until age 3 years. During the last examination, they The results from the study are displayed in this table Low birthweight Normal birthweight 665 Total Delayed Normal Total 975 1585 2560 2250 2250 4500 1275 1940 1. Calculate the risk (incidence per 100, 1 decimal) of developmental delays among: (1pt each) a. Those with low birthweight: b. Those with normal birthweight Calculate the relative risk (RR) of developmental delay for those with low birth weight compared to those with normal birth weight. (2 decimal places) (2pts) 2. In one sentence, explain what this RR tells us about the risk of developmental delays and low birthweight in this hypothetical study. (1pt) 3. Calculate the risk difference (RD) to show how much risk is attributable to low birthweight among those who had this exposure. (1pt) 4.Explanation / Answer
Solution
(1) (a) risk with low birthweight = 2250/4500 = 0.5
(b) risk with normal birthweight = 2250/4500 = 0.5
(2) relative risk = (1275/2250)/(665/2250 ) = 1.92
(3) In this study children with delayed lowbirthwieght had 1.92 times the risk of the normal birthweight
(4) RD = 1275/2250 - 665/2250 = 0.27
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