Left nucleus accumbens volume is associated with poor sleep in hip osteoarthritis

Reduction in the volume of the nucleus accumbens (NAc) has emerged as a promising signature of chronic pain transition, including in osteoarthritis (OA). Yet, less is known about the factors that could influence these changes in the mesolimbic system. Given that poor sleep is common in OA, and recent studies of sleep disturbance on pain perception in animals and healthy populations have specifically implicated the NAc, we hypothesised that the left NAc volume in hip OA would be associated with sleep quality and quantity. Furthermore, we explored how sex interacts with this relationship.

Cross-sectional study in participants with hip OA (n = 34; aged 60+/-12 years, 67 % females) who reported moderate pain were recruited.

A one-sample t-test showed that the left NAc volumes were significantly lower than normative values (t = -2.7368, df = 33, p-value = 0.009). In a model (F(4, 29) = 6.642, p < 0.001, R2 = 0.4781) including the total intracranial volume (TIV), sex and age, the left NAc volume was significantly predicted by sleep quality (t = -3.416, p = 0.002) assessed with Pittsburgh Sleep Quality Index (PSQI). Sleep efficiency (t = 2.362, p = 0.025) but not hours spent in bed (p > 0.05) was also a significant predictor. With models exploring sleep*sex interactions, only sleep efficiency demonstrated an interaction, suggesting that the left NAc volume is lower in females with worse sleep efficiency (t = -2.086, p = 0.046, albeit not significant when corrected for multiple comparisons, pFDR = 0.138.).

Our results suggest that the reduction of the NAc volumes as a candidate biomarker of pain might be influenced by sleep. This exploratory finding in a chronic hip OA population is consistent with the results previously only reported in animal and experimental pain/sleep studies in healthy participants.

The left NAc as a candidate biomarker of chronic pain is sensitive to the effects of sleep quality, especially in females with OA.