Methodology &Study Designs part4

•Disadvantages of Cohort studies
1.Not suitable for rare disease.
2.Long – term follow up may be needed when the latency period for outcome of interest is long .
3.Attrition or loss of people from the sample during the course of the study.
4.Time consuming .
5.Expensive .
6.The exposure status may change during the conduct of the study

Time Frame Cross-sectional:
– data are collected at one point in time, often in order to make comparisons across different types of respondents or participants. Prospective (longitudinal):
–data are collected on multiple occasions starting with the present and going into the future for comparisons across time. Retrospective:
–look back in time using existing or available data to explain or explore an existing occurrence.
Time Frame Cross-sectional:
– data are collected at one point in time, often in order to make comparisons across different types of respondents or participants. Prospective (longitudinal):
–data are collected on multiple occasions starting with the present and going into the future for comparisons across time. Retrospective:
–look back in time using existing or available data to explain or explore an existing occurrence.
Time Frame Cross-sectional:
– data are collected at one point in time, often in order to make comparisons across different types of respondents or participants. Prospective (longitudinal):
–data are collected on multiple occasions starting with the present and going into the future for comparisons across time. Retrospective:
–look back in time using existing or available data to explain or explore an existing occurrence.