Reduced Slow-Wave Sleep and Altered Diurnal Cortisol Rhythms in Patients with Addison's Disease

Cortisol plays a key role in initiating and maintaining different sleep stages. Patients with Addison's disease (AD) frequently report disrupted sleep, and their hydrocortisone medication regimes do not restore the natural diurnal rhythm of cortisol. However, few studies have investigated relations between sleep quality, especially as measured by polysomnographic equipment, and night-time cortisol concentrations in patients with AD.

We used sleep-adapted EEG to monitor a full night of sleep in 7 patients with AD and 7 healthy controls. We sampled salivary cortisol before bedtime, at midnight, upon awakening, and at 30-minutes post-waking.

Controls had lower cortisol concentrations than patients before bedtime and at midnight. During the second half of the night, patient cortisol concentrations declined steeply, while control concentrations increased steadily. Whereas most controls experienced a positive cortisol awakening response, all patients experienced a decrease in cortisol concentrations from waking to 30-minutes post-waking (P = .003). Patients experienced significantly lower proportions of slow-wave sleep (SWS; P = .001), which was associated with elevated night-time cortisol concentrations.

Overall, these results suggest that patients with AD demonstrate different patterns of night-time cortisol concentrations to healthy controls, and that relatively elevated concentrations are associated with a reduction of SWS. These hormonal and sleep architectural aberrations may disrupt the routine sleep-dependent processes of memory consolidation, and hence may explain, at least partially, the memory impairments often experienced by patients with AD.