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

UNLABELLED: 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.

Preclinical episodes of orofacial pain symptoms and their association with health care behaviors in the OPPERA prospective cohort study.

The course of preclinical pain symptoms sheds light on the etiology and prognosis of chronic pain. We aimed to quantify rates of developing initial and recurrent symptoms of painful temporomandibular disorder (TMD) and to evaluate associations with health behaviors. In the OPPERA prospective cohort study, 2,719 individuals aged 18 to 44years with lifetime absence of TMD when enrolled completed 25,103 quarterly (3-monthly) questionnaires during a median 2.3-year follow-up period. Questionnaires documented TMD symptom episodes, headache, other body pain, health care attendance, and analgesic use, and. Kaplan-Meier methods for clustered data estimated symptom-free survival time. Multivariable models assessed demographic variation in TMD symptom rates and evaluated associations with health care and analgesic use. One-third of the study subjects developed TMD symptoms and for a quarter of symptomatic episodes, pain intensity was severe. Initial TMD symptoms developed at an annual rate of 18.8 episodes per 100 persons. The annual rate more than doubled for first-recurrence and doubled again for second or subsequent recurrence such that, 1year after first recurrence, 71% of study subjects experienced a second recurrence. The overall rate increased with age and was greater in African Americans and lower in Asians relative to those of white race/ethnicity. The probability of TMD symptoms was strongly associated with concurrent episodes of headache and body pain and with past episodes of TMD symptoms. Episodes of TMD symptoms, headache, and body pain were associated with increases of ∼10% in probability of analgesic use and health care attendance. Yet, even when TMD, headache, and body pain occurred concurrently, 27% of study subjects neither attended health care nor used analgesics.

Study methods, recruitment, sociodemographic findings, and demographic representativeness in the OPPERA study.

UNLABELLED: This paper describes methods used in the project "Orofacial Pain Prospective Evaluation and Risk Assessment" (OPPERA) and evaluates sociodemographic characteristics associated with temporomandibular disorders (TMD) in the OPPERA case-control study. Representativeness was investigated by comparing sociodemographic profiles of OPPERA participants with population census profiles of counties near study sites and by comparing age and gender associations with TMD in OPPERA and the 2007 to 2009 US National Health Interview Survey. Volunteers aged 18 to 44 years were recruited at 4 US study sites: 3,263 people without TMD were enrolled into the prospective cohort study; 1,633 of them were selected as controls for the baseline case-control study. Cases were 185 volunteers with examiner-classified TMD. Distributions of some demographic characteristics among OPPERA participants differed from census profiles, although there was less difference in socioeconomic profiles. Odds of TMD was associated with greater age in this 18 to 44 year range; females had 3 times the odds of TMD as males; and relative to non-Hispanic-Whites, other racial groups had one-fifth the odds of TMD. Age and gender associations with chronic TMD were strikingly similar to associations observed in the US population. Assessments of representativeness in this demographically diverse group of community volunteers suggest that OPPERA case-control findings have good internal validity. PERSPECTIVE: Demographic associations with TMD were consistent with population benchmarks and with other studies, suggesting broad applicability of these OPPERA findings. Greater occurrence of TMD in non-Hispanic-Whites than in other racial/ethnic groups and the lack of a socioeconomic gradient contradicts the disparities seen in many other health conditions.