Abstract
The attrition rate of longitudinal study participation remains a challenge. To date, the Malaysian Cohort (TMC) study follow-up rate was only 42.7%. This study objective is to identify the cause of attrition among TMC participants and the measures to curb it. A total of 19,343 TMC participants from Kuala Lumpur and Selangor that was due for follow-up were studied. The two most common attrition reasons are undergoing medical treatment at another government or private health center (7.0%) and loss of interest in participating in the TMC project (5.1%). Those who were inclined to drop out were mostly Chinese, aged 50 years and above, unemployed, and had comorbidities during the baseline recruitment. We have also contacted 2183 participants for the home recruitment follow-up, and about 10.9% agreed to join. Home recruitment slightly improved the overall follow-up rate from 42.7% to 43.5% during the three-month study period.
Highlights
The challenges in a cohort study include the relatively high cost due to the prospective nature of the study [1], the labor-intensive follow-up process [2], and the drop in the response during follow-up [3]
During follow-up, the attrition rate of participants is crucial, as it might introduce a certain form of selection bias to the overall cohort study [5,6] and probably lead to the loss of statistical power in the analysis [7,8,9]
Attrition can be considered missing not at random (MNAR), which might influence the result of the analysis due to bias [10,11,12,13]
Summary
The challenges in a cohort study include the relatively high cost due to the prospective nature of the study [1], the labor-intensive follow-up process [2], and the drop in the response during follow-up [3]. During follow-up, the attrition rate of participants is crucial, as it might introduce a certain form of selection bias to the overall cohort study [5,6] and probably lead to the loss of statistical power in the analysis [7,8,9]. Some consistent findings related to attrition rate in longitudinal studies were aging, being a woman, fewer years of education, lower economic status, frailty, poor health, not having a family history of dementia, and cognitive impairment [14,15,16,17,18,19,20]. Several neuropsychological tasks, such as having slower processing speed, less attentional flexibility, worse delayed verbal recall, and MRI markers, were associated with the attrition rate that might presumably be mediated by cognitive skills [16,21,22]
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