Andre Meichtry:  Back pain and depression across 11 years Analysis of Swiss Household Panel data

Adviser: Prof. Dr. Werner Stahel

Co-Adviser: PD Dr. Thomas Läubli

December 2011

Abstract:

Design and objective: In this longitudinal retrospective cohort study, we analysed back pain and depression data across 11 years in the general population of Switzerland. The main objective was to investigate the association between back pain and depression.

Methods: We used data from the Swiss Household Panel. 7799 individuals (aged 13- 93, mean 42.9 years, 56.2% women) were interviewed between 1999 and 2009. Observed depression and back pain were described across 11 years. Missingness was assumed to be independent of unobserved data. We estimated marginal structural models using inverse-probability-of-exposure-and-censoring weights to assess the (causal) association between back pain history and depression. Correlated data was analysed by fitting marginal and transition models with generalised estimating equations yielding robust sandwich variance estimates.

Results: Cross-sectional analysis adjusting for other time-fixed covariates showed that back pain was associated with a 42% increase in the odds of depression over time. The association of continuous past back pain up to time t−1 with depression at time t was 0.65 on a linear logistic scale (95% CI: 0.48-0.82), corresponding to a 92% (62-127%) increase in the odds of depression. Assuming a causal model accounting for confounded back pain by past depression, a marginal structural model (inverse-probability-of-exposure-and-censoring weighted model) regressing depression on past back pain showed an association of 0.63 (0.44-0.81) on a linear logistic scale, corresponding to a 87% (55-126%) increase in the odds of depression. Expressing exposure history by cumulative back pain up to time t-1, marginal structural model estimated a causal effect on depression at time t that increased with age at baseline and decreased for individuals with depression at baseline.

Conclusion: Marginal structural models are well suited for the analysis of observational longitudinal data with time-dependant potential causes of depression, however,  marginal structural models do not address all issues of causal inference. Back pain history is one of many possible causes of depression. Future work must collect more socio-economic and health-related covariates, investigate possible non-ignorable missing and investigate other functions of back pain history.

Download pdf (842 KB)