Purpose: Increasing evidence, primarily from animal studies and patients with compromised neurotransmitter systems, indicates a possibly important role for dopamine in modulating sleep. We therefore conducted this study to explore the relation between sleep and dopamine in healthy adults.
Methods: We used the Pittsburgh Sleep Quality Index (PSQI) to assess sleep quality. Higher PSQI scores indicate a lower quality of sleep. Striatal dopamine D2/D3 receptor availability was determined using [123I]iodo-benzamide (IBZM) SPECT. Fifty-five healthy volunteers (32 men, 23 women; mean age, 36.7+/-12.1 years), including 25 good sleepers and 30 poor sleepers, were recruited. We analysed the correlation between the PSQI and D2/D3 receptor availability in good and poor sleepers based on Pearson's product-moment after removing the effects of gender and age. We also analysed differences in D2/D3 receptor availability between good and poor sleepers.
Results: In poor sleepers, there was no statistically significant relationship between the global, individual components of the PSQI score and D2/D3 receptor availability. However, in good sleepers, the score of the sleep duration component was significantly negatively correlated with D2/D3 receptor availability in the caudate. There was no significant difference in D2/D3 receptor availability between good and poor sleepers.
Conclusion: Our findings demonstrate that healthy good sleepers with higher D2/D3 receptor availability in the caudate sleep longer. Poor sleep in healthy subjects might be not primarily related to the dopaminergic system.