Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, C74
The effect of ageing on the control of breathing: a role for the development of obstructive sleep apnoea.
K. Pugh1, G. Balanos1, S. Taheri1, H. Griffin1
1. School of Sports and Exercise Sciences, University of Birmingham, Birmingham, United Kingdom.
Obstructive sleep apnoea (OSA) is a condition characterised by the frequent collapse of the upper airway during sleep. OSA is common among the general population, with one in fifteen adults presenting with moderate to severe OSA, but is much more prevalent among older individuals, affecting almost half of those aged over 60. One suggested mechanism for this striking prevalence in the elderly population is a change in the sensitivity of the control of breathing during sleep. (Younes, Ostrowski et al. 2001; Wellman, Malhotra et al. 2007). Existing research on the causal properties of chemical drive in the development and/or progression of OSA do not take into account the alterations in chemical drive brought about by OSA itself and chronic changes in ventilatory control that may persist post-treatment. Furthermore, most studies use inadequate re-breathing methods for eliciting ventilatory responses and/or the choice of middle-aged participants is flawed since this is not the population most at risk of OSA development. In the present study, our main aim was to investigate the effect of ageing on chemosensitivity by measuring the ventilatory responses of young (18-30 years) and old (60-75 years) participants. A second aim was to investigate the differences in ventilatory control in the older population, between those who were free of sleep disorders (non-snorers and apnea-hypopnea index (AHI) = 0), and those suffering from very mild sleep disorders (snorers and AHI<10). The presence of any form of sleep apnoea and/or snoring was tested using at home testing equipment (ResMed Apnealink). This allowed us to map the role of chemosensitivity in the evolution of sleep disorders in the elderly population. To evaluate chemosensitivity we used a hypercapnia multi-frequency-binary sequence (MFBS) challenge (Pedersen, Fatemian et al. 1999). A MFBS test involves a number of hypercapnic steps (10mmHg>resting Pco2) of varying duration. The hypercapnic steps were achieved using a dynamic end-tidal forcing system. Po2 was controlled at 100mmHg throughout the test. Using the MFBS test the contributions of peripheral and central chemoreceptors in ventilatory control can be assessed. Preliminary results showed a 15.3±6% reduction in the combined sensitivity of peripheral & central chemoreceptors when older healthy participants were compared to younger healthy individuals. In addition, when older participants with very mild symptoms of sleep disorder were compared with asymptomatic age-matched individuals, a 9.2±2% reduction in combined sensitivity was found. These results suggest a reduction in chemosensitivity with age. When this attenuation becomes too low it could play a role in the development of sleep disordered breathing.
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