Assessing nonresponse bias at follow-up in a large prospective cohort of relatively young and mobile military service members

Seattle Epidemiologic Research and Information Center, Department of Veterans Affairs Puget Sound Health Care System, Seattle, WA, USA.
BMC Medical Research Methodology (Impact Factor: 2.27). 10/2010; 10(1):99. DOI: 10.1186/1471-2288-10-99
Source: PubMed


Nonresponse bias in a longitudinal study could affect the magnitude and direction of measures of association. We identified sociodemographic, behavioral, military, and health-related predictors of response to the first follow-up questionnaire in a large military cohort and assessed the extent to which nonresponse biased measures of association.
Data are from the baseline and first follow-up survey of the Millennium Cohort Study. Seventy-six thousand, seven hundred and seventy-five eligible individuals completed the baseline survey and were presumed alive at the time of follow-up; of these, 54,960 (71.6%) completed the first follow-up survey. Logistic regression models were used to calculate inverse probability weights using propensity scores.
Characteristics associated with a greater probability of response included female gender, older age, higher education level, officer rank, active-duty status, and a self-reported history of military exposures. Ever smokers, those with a history of chronic alcohol consumption or a major depressive disorder, and those separated from the military at follow-up had a lower probability of response. Nonresponse to the follow-up questionnaire did not result in appreciable bias; bias was greatest in subgroups with small numbers.
These findings suggest that prospective analyses from this cohort are not substantially biased by non-response at the first follow-up assessment.

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Available from: Gary D Gackstetter
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    • "Even though only few in the target population participated, the main effect of non-participation was a loss of precision in stratum-specific estimates [26]. Similar conclusions were drawn in a prospective cohort study, in which it was found that a prospective analysis in a cohort of relatively young, highly mobile, adult military personnel was not substantially biased by non-response at the first follow-up after four years [27]. "
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    • "The study population consisted of the entire study samples for Panels 2 and 3 of the Millennium Cohort Study, except those who refused to participate. Panel 1 was enrolled during 2001-2003 and consisted of 77,047 (30%) participants from a probability-based sample of 256,400 military personnel who had at least 1 year of service as of October 1, 2000; this panel has previously been studied in terms of nonresponse to enrollment [24] and follow-up [9] in relation to health status. For Panel 2, 150,000 randomly selected military personnel with 1-2 years of service as of October 2003 were invited. "
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    • "More specifically, several studies have been undertaken on the non-response to health interview surveys (HIS). Previous studies find that respondents have a higher socio-economic status and that they report a better subjective health, lower healthcare use, and healthier lifestyle behaviour than non-respondents [19-28]. However, other studies find higher healthcare use for respondents or better health status for non-respondents [29-33]. "
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