Abstract

Objectives

Multimorbidity poses various challenges, and previous research has indicated a causal relation with depression. As multimorbidity is not curable, the underlying mechanisms are of great interest. Positive affect is a major resource for coping with chronic conditions and for the prevention of depression. Long-term multimorbidity, however, may deplete positive affect. The purpose of this paper is to investigate the role of positive affect in the association between multimorbidity and depressive symptoms.

Method

We used four consecutive waves (2008, 2011, 2014, 2017) of the nationally representative German Ageing Survey (DEAS) with a total of 1,558 older adults aged 40 and over. To account for time-varying confounding, exposure-induced mediator-outcome confounding, and reciprocities, we applied the mediational g-formula with inverse-probability weighting techniques. We also tested for exposure-mediator interaction to adjust for differences in mediation across the duration of multimorbidity.

Results

We confirmed a positive longitudinal relation between multimorbidity and depressive symptoms, both of which were negatively associated with while positive affect. The model without interaction indicated a share mediated of ca. 18.3% on the total effect of multimorbidity on depressive symptoms. Addition of interaction led to substantial differences for multimorbidity duration and levels of positive affect. Associations for long-term multimorbidity (at least two survey waves) were more substantial, and the share mediated doubled (>40%). Additionally, the direct effect of multimorbidity on depressive symptoms diminished for short-term multimorbidity.

Conclusion

Strengthening positive affect could reduce depressive symptoms in those facing multimorbidity. This study also discusses methodological challenges in performing longitudinal mediation analysis. We advise researchers to consider the mediational g-formula and exposure-mediator interaction.

中文翻译：

---

积极影响是否介导抑郁症的多发病率关联？

摘要

目标

多发病率提出了各种挑战，以前的研究表明与抑郁症之间存在因果关系。由于无法治愈多种疾病，因此潜在的机制引起了极大的兴趣。积极影响是应对慢性病和预防抑郁的主要资源。但是，长期的多发病可能会耗尽积极的影响。本文的目的是研究积极影响在多发病和抑郁症状之间的关系。

方法

我们连续四次（2008年，2011年，2014年，2017年）使用了具有全国代表性的德国老龄化调查（DEAS），共计1,558名40岁以上的老年人。为了解决随时间变化的混杂，暴露引起的中介者-结果混杂以及互惠，我们使用具有反概率加权技术的中介g公式。我们还测试了暴露-调节剂之间的相互作用，以调整多重发病期间的调节差异。

结果

我们证实了多发病与抑郁症状之间呈正向纵向关系，两者与积极影响呈负相关。没有交互作用的模型表明约有介导的份额。多发症对抑郁症状总效果的18.3％。相互作用的增加导致多种疾病的持续时间和积极影响水平存在实质性差异。长期多重发病率（至少两次调查）的关联更为广泛，所介导的份额增加了一倍（> 40％）。此外，多发病对抑郁症状的直接影响因短期多发病而减弱。

结论

增强正面影响可以减轻那些患有多种疾病的人的抑郁症状。这项研究还讨论了进行纵向调解分析的方法学挑战。我们建议研究人员考虑介导的g公式和暴露介导的相互作用。