Ethnic background as a factor in temporomandibular disorder complaints

AIMS: To examine the associations between the ethnic backgrounds of temporomandibular disorder (TMD) patients in the Netherlands and the level of TMD pain complaints and psychological/behavioral factors and whether these associations are influenced by socioeconomic factors.
METHODS: A sample of 504 consecutive patients from a TMD clinic completed the Research Diagnostic Criteria for TMD (RDC/TMD) Axis II questionnaire (pain intensity, pain-related disability, somatization, depression, ethnic background, and socioeconomic status), an oral parafunctions questionnaire, and questions related to stress. Ethnic background was classified, following the method of Statistics Netherlands (CBS), using the country of birth from subject and both parents. This resulted in a classification into three subgroups: Native Dutch (ND; 69.6%), Non-Native Western (NNW; 14.8%), and Non-Native Non-Western (NNNW; 15.6%). Statistics used were chi-square, one- and two-way ANOVA, and Kruskall-Wallis tests; for post-hoc interpretation, standardized residual values, Bonferroni, and Mann-Whitney U tests were used.
RESULTS: No differences in age or gender were found between the three ethnic groups, nor were there any differences in characteristic pain intensity or oral parafunctions. However, TMD patients from the NNNW subgroup had significantly higher scores on psychological factors, namely pain-related disability, disability days, somatization, depression, and stress. These patients had a lower incidence of employment, a lower level of education, and a lower income level than patients from the ND and NNW ethnic backgrounds. Analysis of variance showed no interaction effects between ethnic background and socioeconomic factors in relation to the psychological variables mentioned.
CONCLUSION: Ethnic background of TMD patients in the Netherlands is associated with psychological factors, regardless of socioeconomic status, but not with TMD pain complaints or oral parafunctions.