Rosemary Gibson

Hypothalamic-Pituitary-Adrenal Axis Activation in Obstructive Sleep Apnea: The Effect of Continuous Positive Airway Pressure Therapy

CONTEXT Obstructive sleep apnea (OSA) is a common condition with significant cardiovascular and metabolic comorbidity. We hypothesized that these may result from OSA-induced perturbations of endogenous ultradian hypothalamic-pituitary-adrenal axis activity. OBJECTIVE The aim of the study was to investigate ACTH and cortisol ultradian patterns using an automated, repetitive blood sampling technique. DESIGN Samples for ACTH and cortisol were collected from 10 patients with moderate to severe OSA under basal conditions, at 10-min intervals over 24 h, at diagnosis and 3 months after compliant continuous positive airway pressure (CPAP) therapy. Multiple-parameter deconvolution estimated specific measures of ACTH and cortisol pulsatile secretion from blood hormone concentrations. RESULTS Mean total ACTH and cortisol production were elevated pre-CPAP compared to post-CPAP (ACTH, 1459.8 +/- 123.0 vs. 808.1 +/- 97.9 pg/ml, P < 0.001; cortisol, 5748.9 +/- 364.9 vs. 3817.7 +/- 351.7 nmol/liter, P < 0.001) as were mean total pulsatile production (ACTH, 764.1 +/- 86.3 vs. 383.5 +/- 50.0 pg/ml, P = 0.002; cortisol, 4715.9 +/- 253.3 vs. 3227.7 +/- 258.8 nmol/liter, P < 0.001). ACTH and cortisol secretory burst mean half-duration were higher at diagnosis (12.3 +/- 0.7 and 13.5 +/- 0.7 vs. 7.8 +/- 0.4 and 8.4 +/- 0.6 min, respectively, P < 0.001); thus, 95% of each ACTH secretion occurred in 21.0 +/- 1.2 vs. 12.9 +/- 0.8 min post-CPAP (P < 0.001) and for cortisol in 23.0 +/- 1.2 vs. 14.2 +/- 1.1 min post-CPAP (P < 0.001). Approximate entropy (ApEn) revealed greater disorderliness in both ACTH (P = 0.03) and cortisol (P = 0.001) time series pre-CPAP. Forward and reverse cross-ApEn suggested nodal disruption at central and adrenal levels pre-CPAP (P = 0.01). Significantly elevated cortisol responses to a single breath of 35% CO(2) occurred pre-CPAP (P = 0.006). CONCLUSIONS Untreated compared to treated OSA is associated with marked disturbances in ACTH and cortisol secretory dynamics, resulting in prolonged tissue exposure to disordered, elevated hormone levels.

Plasma apelin levels in obstructive sleep apnea and the effect of continuous positive airway pressure therapy

Apelin is a peptide hormone with cardiovascular and glucose homeostasis properties, and obstructive sleep apnea (OSA) is complicated by cardiovascular and metabolic comorbidities. Plasma apelin has not been previously assessed in OSA. We investigated the response of plasma apelin to a 2-h 75 g oral glucose tolerance test (OGTT) and the effect of 3 months compliant continuous positive airway pressure (CPAP) therapy in 15 obese males with newly diagnosed OSA. Plasma apelin and serum cortisol were recorded 10 minutely, while serum insulin and glucose were measured 30 minutely. Ten subjects had plasma apelin measured at intervals across a 24-h period to investigate for circadian variation in apelin levels, and this was repeated following 3 months compliant CPAP therapy. Fasting (0.342+/-0.038 vs 0.288+/-0.024 ng/ml, P=0.04), 30 min (0.399+/-0.035 vs 0.312+/-0.036 ng/ml, P=0.007) and 120 min (0.402+/-0.030 vs 0.259+/-0.024 ng/ml, P<0.001) apelin levels were reduced following CPAP. The area under curve for apelin OGTT response was lower post-CPAP (44.1+/-3.3 vs 35.8+/-2.3 ng/ml per min, P<0.001). Mean OGTT apelin levels showed a significant treatment effect (P=0.006) and a time effect (P<0.001), and the effect of time was different pre- versus post-CPAP (P=0.005). No significant variability in apelin levels existed across the 24-h period at diagnosis. Lower levels were evident overnight following treatment (P=0.004). Improvements in insulin and glucose parameters and reduced cortisol levels were found post-CPAP. In summary, untreated OSA was associated with elevated plasma apelin levels, altered apelin secretory dynamics in response to oral glucose and lack of an apparent circadian variability, which was restored following CPAP.

Understanding the sleep problems of people with dementia and their family caregivers

Sleep disturbances are common with dementia and can adversely affect waking function. However, the perspectives of people with dementia and their family caregivers concerning their sleep are under-researched. We conducted three focus groups with 12 community-dwelling pairs (a person with dementia and their family caregiver). Discussions addressed sleep disturbances, coping strategies, and beliefs and attitudes surrounding sleep. Thematic analysis indicated that dementia-related sleep disturbances were common, including confused awakenings and dementia-related behaviors at night, changes to sleep timing, and nightmares. Common issues for caregivers included being woken at night, having problems getting back to sleep, trips to the bathroom, and daytime sleepiness. Participants often normalized their sleeping problems and had developed a number of coping strategies. These findings highlight the impact that sleep disturbances can have on people living with dementia. Their experiences and beliefs need to be considered for developing effective interventions to improve sleep, waking function, and wellbeing.

Effect of caregiving status on the sleep of older New Zealanders.

To investigate relationships between caregiving and subjective sleep reports among older New Zealanders.

Non-pharmacological interventions for managing dementia-related sleep problems within community dwelling pairs: A mixed-method approach

Dementia-related sleep problems can be complex and challenging. Environmental interventions which resynchronise the sleep/wake cycle have been trialled with promising results for people with dementia in institutionalised settings. However, there is less research concerning community-dwelling people with dementia and their family carers. This study involved a five-week feasibility study including timed light therapy, exercise and sleep education. Sleep and physical and mental functioning were measured at the beginning and end of the trial using objective measures, standardised questionnaires and structured participant feedback. Of 15 community-dwelling pairs who participated, nine completed the trial. The case studies presented here reveal that it is feasible for this population to use non-pharmacological interventions, with positive outcomes. However, there are also issues that can mask benefits or prevent compliance. The options for treating dementia are limited. Environmental interventions may help manage dementia-related sleep problems and further trials would be worthwhile to improve compliance and evaluate effectiveness.