The association between Type D personality and insomnia in breast cancer patients

Abstract

Background: Type D personality, the combination of negative affectivity (NA) and social inhibition (SI), is associated with poor clinical outcome in various patient groups. For example, research has identified that Type D is associated with poor mental health and quality of life in cancer patients. Disturbances in sleep represent another common consequence of cancer diagnosis, but to-date, no study has investigated the association between Type D and sleep problems in cancer patients. Methods: In a longitudinal study, 108 female breast cancer patients completed self-report measures of Type D personality (DS14) and insomnia severity (ISI) four years post-diagnosis. The relationship between Type D and insomnia was investigated using both the traditional categorical method of analysing Type D and the dimensional method of analysis (utilising the NAxSI interaction term). Findings: Analysis showed that 18% of the sample had a Type D personality, and that these patients (M=9.7, SD=6.9) had significantly higher levels of insomnia than non-Type D patients (M=6.4, SD=6.1, t (105)=2.09, p<.05). In addition, dimensional analysis showed that Type D (NAxSI) was significantly correlated with higher levels of insomnia (r=.224, p<.05). However, on examination of the NA and SI components of Type D, it was found that only NA (and not SI) was significantly associated with insomnia (r=.505, p<.001). Discussion: The results demonstrate that although Type D breast cancer patients have elevated levels of insomnia, these elevated levels are associated solely with the NA component of Type D, as opposed to the interaction between NA and SI, which delineates Type D.