Question

A cross-sectional study was conducted on the association between passive smoke inhalation and the occurrence of dental caries in children. (Passive smoke exposure occurs when children live with family members who smoke.) The investigators thought that conclusions from this study were limited because of the cross-sectional nature of the data. Suppose that they asked you for advice and you told them that they should have conducted a prospective cohort study because it is a better study design.

a. Briefly describe the specific limitation of a cross-sectional study is avoided by conducting a prospective cohort study.

b. The investigators take your advice and hire you to help them design a new prospective cohort study. They want to know if they should use a special or a general cohort to assemble the exposed population. Briefly describe each of these options, tell them which one is best in this setting, and explain your reasons.

c. The investigators also ask you about the options for selecting a comparison group in a cohort study. Briefly describe the three different options and state which one is best in this setting and why.

Answer 1

a )

The cross sectional study, cohort study are all observational studies. It also includes case control studies.

The investigators thought that the cross sectional studies are limited because it determines prevalance. This study does not distinguish between cause and effect althogh it is easy and quick. Whereas, The cohort study delivers incidents, causes and effects separately. This reords the events in chronological order. It is vital to determine the type of study in any event.

EVery study should be described with key points for better analyzing as the key points are used as reference for every event study.

For example in the above event, the conclusion is that "passion smoke expsore occurs when cildren live with the family members who smoke" This clearly states only the cause of the passive smoke inhalation but the effect is not clearly concluded. If this was studied with cohort then the event will recoreded in chronological order which will help us determine the other reasons as well and its effect in a better way.

b )

“A generational group, often referred to as a cohort, includes those who share historical or social life experiences, the effects of which are relatively stable over the course of their lives. These life experiences tend to distinguish one generation from another

Here, special cohort will be used because of special circumstances of passive smoking.

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