Association between tendency towards depression and severity of rheumatoid arthritis from a national representative sample: the Medical Expenditure Panel Survey

Abstract

Objectives:

The association between RA and depression has been well documented but so far there is not much research at a national level and none using a quick classification system of RA. The purpose of this study is to further determine if this association varies by differing severity in functional status of RA patients.

Methods:

This study involved a retrospective pooled cross-sectional analysis of the Household Component of Medical Expenditure Panel Survey (MEPS) for the years 2004–2006. Each year’s medical conditions file was merged with the person-level consolidated file. A total of 289 individuals comprised the final adult sample of RA and related diseases. RA cases were classified into four classes of functional status according to the ACR classification criteria. Tendency towards depression was ascertained by Patient Health Questionnaire (PHQ-2) scores with scores greater than or equal to three classified as high tendency towards depression. Multivariate logistic regression with survey weights was done using SAS 9.1.

Results:

After controlling for other relevant factors, patients belonging to Class III RA were 5.92 times more likely and those belonging to Class II RA were 3.78 times more likely to have high tendency towards depression as compared to Class I RA patients. Older age groups (≥68 years) and physical activity were other significant predictors but in a negative direction, whereas a co-morbidity index of two showed a significant positive association.

Conclusion:

The study provides important evidence that in a nationally representative sample of US non-institutionalized civilians, there is a strong association of depression to RA and related diseases by functional severity. However, the findings should be interpreted with caution because the data does not offer any information on duration in relation to PHQ-2 scores, thus making it hard to deduce if tendency towards depression was present before the diagnosis of RA. Furthermore, disease-specific and data-specific validation of the Charlson comorbidity index has not been done which leaves the possibility of residual confounding.

Key words::

• ACR
• Depression
• MEPS
• Rheumatoid arthritis

Transparency

Declaration of funding

This study was partially funded by the Tulane Research Enhancement Fund. D.G. conceived of the study, participated in its design, the analytical plan, statistical analysis, interpretation of the results, and led in writing the manuscript. L.S. was the advisor for the study (conceptualization, SAS programming guidance, interpretation of the results, and manuscript preparation). H.M. conceived of the study, participated in its design and contributed in the early stages of the manuscript.

Declaration of financial/other relationships

The authors have disclosed no relevant financial relationships. Peer reviewers may receive honoraria from CMRO for their review work. The peer reviewers have disclosed no relevant financial relationships.

Acknowledgments

The authors would like to acknowledge the assistance of Dr. Janet Rice in providing statistical guidance on methods (design-based and model-based) used in evaluating complex survey analysis, and Bridget Lavin for reviewing and providing valuable feedback on the manuscript. The authors would also like to thank unknown reviewers whose insightful comments have helped in making this a better study.

An earlier simpler version was presented as a poster at the Academy Health annual meeting, Washington DC, 2008.