Pain, psychological variables, sleep quality, and natural killer cell activity in midlife women with and without fibromyalgia.

In women with fibromyalgia (FM), central nervous system (CNS) dysfunction in pain, mood, and sleep processes could be associated with changes in immune system indicators. The primary purpose of this study was to compare pain, psychological variables, subjective and objective sleep quality, lymphocyte phenotypes and activation markers, and natural killer activity (NKA) in midlife women with and without FM. A secondary purpose was to explore relationships among these variables in a step-wise regression. Subjects had pain pressure tender points assessed, completed a psychiatric interview and questionnaires (Beck Depression Inventory, SCL-90, Profile of Mood States, subjective sleep), and underwent polysomnograhic assessment for two consecutive nights. Lymphocyte phenotypes, activation markers, and NKA were assessed from blood drawn the morning after sleep laboratory night 2. Compared to controls, women with FM had lower pain thresholds, more psychological distress, higher depression scores, and reduced subjective and objective sleep quality. They also had fewer NK cells (p <.009) and more NK cells that expressed the IL-2 receptor (p <.04), but these differences were not statistically significant after correction for multiple comparisons. NKA was not statistically significantly lower in the women with FM compared to controls. In a multiple regression of age, tender point threshold, depression, psychological distress, and sleep efficiency, only the effect of group was significant (F = 5.479, p <.03) on NKA. In conclusion, we found little evidence to support the hypothesis that pain, mood, and sleep symptoms are associated with changes in the enumeration of peripheral lymphocytes or function in FM.