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Observational Study
. 2013 Dec;14(12 Suppl):T2-19.
doi: 10.1016/j.jpain.2013.06.006.

Study protocol, sample characteristics, and loss to follow-up: the OPPERA prospective cohort study

Eric Bair  1 , Naomi C Brownstein, Richard Ohrbach, Joel D Greenspan, Ronald Dubner, Roger B Fillingim, William Maixner, Shad B Smith, Luda Diatchenko, Yoly Gonzalez, Sharon M Gordon, Pei-Feng Lim, Margarete Ribeiro-Dasilva, Dawn Dampier, Charles Knott, Gary D Slade
Affiliations
Observational Study

Study protocol, sample characteristics, and loss to follow-up: the OPPERA prospective cohort study

Eric Bair et al. J Pain. 2013 Dec.

Abstract

When studying incidence of pain conditions such as temporomandibular disorder (TMD), repeated monitoring is needed in prospective cohort studies. However, monitoring methods usually have limitations and, over a period of years, some loss to follow-up is inevitable. The OPPERA prospective cohort study of first-onset TMD screened for symptoms using quarterly questionnaires and examined symptomatic participants to definitively ascertain TMD incidence. During the median 2.8-year observation period, 16% of the 3,263 enrollees completed no follow-up questionnaires, others provided incomplete follow-up, and examinations were not conducted for one third of symptomatic episodes. Although screening methods and examinations were found to have excellent reliability and validity, they were not perfect. Loss to follow-up varied according to some putative TMD risk factors, although multiple imputation to correct the problem suggested that bias was minimal. A second method of multiple imputation that evaluated bias associated with omitted and dubious examinations revealed a slight underestimate of incidence and some small biases in hazard ratios used to quantify effects of risk factors. Although "bottom line" statistical conclusions were not affected, multiply-imputed estimates should be considered when evaluating the large number of risk factors under investigation in the OPPERA study.

Perspective: These findings support the validity of the OPPERA prospective cohort study for the purpose of investigating the etiology of first-onset TMD, providing the foundation for other papers investigating risk factors hypothesized in the OPPERA project.

Keywords: Temporomandibular disorder; cohort studies; epidemiologic methods; population statistics; proportional hazards models.

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Figures

Figure 1
Figure 1
Flowchart of enrollment and follow-up: OPPERA prospective cohort study, 2006 to 2011. *Follow-up data collection continued after examination of people who did not have TMD. Hence, individuals could have more than 1 follow-up examination prior to censoring or developing TMD. †Follow-up data collected after examiner-classified TMD were not used in this analysis.
Figure 2
Figure 2
Tests of proportional hazards assumption: OPPERA prospective cohort study, 2006 to 2011. Quantile-quantile plots of P values from 251 tests of proportional hazards assumption. FDR, false-discovery rate.
Figure 3
Figure 3
Tests of association between baseline characteristics and loss to follow-up: OPPERA prospective cohort study, 2006 to 2011. Quantile-quantile plots of P values from tests of association between 521 people completely lost to follow-up and 2,737 people who completed 1 or more follow-up questionnaires. Dependent variables were 28 measures of pain sensitivity (A), 27 psychological characteristics (B), 51 measures of autonomic function (C), and 42 clinical characteristics (D).
See this image and copyright information in PMC

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