Observational Retrospective Cohort Study

I will choose observational retrospective cohort design for my study.
My research question was to identify the association between socioeconomic, biopsychosocial, environmental and genetic factors, and the development of childhood asthma. To establish the effect of allergen (cockroaches, dust), poverty, poor air ventilation in a house, racial factors and air pollution on developing children asthma, a cohort have to have a exposure and the cohort need to followed over time. Cohort studies are used to study the incidence, causes, natural history of a disease and prognosis.1 Because they measure events in the chronological order, they can be used to distinguish between cause and effect.1 This type of study is the best method for determining the incidence and natural history of a disease or condition.1 One of the advantages of doing retrospective cohort study is that the data already collected for some other research study or purposes. The cohort is “followed up” retrospectively.1 The study period may be many years but the time to complete the study is only as long as

Retrospective cohort studies are much cheaper as the data have already been collected.1 This type of study is the lack of bias because the outcome of current interest was not the original reason for the data to be collected.1 However, because the cohort was originally constructed for another purpose, it is unlikely that all the relevant information will have been rigorously collected. Retrospective cohorts studies have other disadvantages that people with the outcome of interest are more likely to remember certain antecedents or minimize or exaggerate what they now consider being as risk factors (recall bias).1 Sample or population selection and loss to follow-up is a major potential cause of bias.1 Any loss to follow-up can significantly affect the validity of the