Sleep, respiration and ALS

Although the association of amyotrophic lateral sclerosis As reported in this issue, Kimura and colleagues using with disturbances of sleep architecture and with sleep ambulatory equipment in ALS patients without respiratory disordered breathing has been described as early as 1979 or sleep related complaints, have uncovered the presence [1], it is only recently that the call has been made for better of significant respiratory disturbance events in 27% (3 of and more complete research on the assessment of sleep 11) of patients with bulbar form of ALS. The events were behavior in ALS [2]. The renewed interest in sleep described as hypopneas and central or obstructive apneas, disorders in ALS has brought forth several observations with predominance of events during REM sleep in one but spawned even more questions with important implicapatient. This report expands on the findings of Ferguson tions. Specifically, does the identification of sleep disand colleagues who have similarly reported the presence of ordered breathing signify early respiratory muscle inhypopneas predominantly during REM sleep in 44% (8 of volvement and justify early intervention with ventilatory 18) of ALS patients with bulbar involvement, but essensupport? Are ALS patients with early bulbar involvement tially no obstructive sleep apnea [3]. While bulbar sympmore prone to sleep disordered breathing? Do sleep toms may predispose to the development of obstructive disorders cause physiologic changes that may accelerate sleep events, their occurrence in ALS may depend on a the decline of these patients? Alternatively, does nocturnal complex interaction of the extent of bulbar and respiratory ventilatory support slow the decline of lung function? muscle involvement. For instance, the high prevalence Answers to these questions will be necessary to provide a (83%) of orthopnea in the patients of the Ferguson study more rational and consistent approach to the care of ALS suggests significant diaphragmatic muscle weakness. This patients. In this issue, the studies of Kimura and colmay have limited their ability to generate an inspiratory leagues, and Kleopa and colleagues, add to the growing pressure above the closing pressure of the upper airway, knowledge of sleep and respiration in ALS. and therefore may have actually decreased the prevalence The described abnormalities of sleep architecture in of sleep obstructive events. The clustering of the sleep ALS have included increased sleep latency, persistence of disordered events to the REM period is consistent with the EMG activity during paradoxical sleep and slow wave normal shift during REM sleep in the burden of maintainsleep, increased paradoxical sleep latency, and longer and ing ventilation from the respiratory intercostal and accesmore frequent awakenings [1]. Other studies document a sory muscles to the diaphragm [4]. Patients with diareduction in total sleep time, an increase in stage 1 sleep, phragmatic dysfunction from neuromuscular disease would more frequent arousals and stage changes per hour, and therefore be particularly vulnerable to respiratory events decreased REM latency [2,3]. While many factors such as during REM sleep. depression, difficulty in handling secretions, fasciculations, The impact of impaired sleep in patients with ALS cramps and orthopnea may account for these disruptions extends beyond the potential for excessive daytime sleepi[3], sleep disordered breathing may be an additional ness. For instance, even in healthy volunteers, sleep contributor. deprivation has been found to have a negative impact on spirometric tests and muscle endurance, with decreases in ventilatory response to hypercapnia [5,6]. The implications *Corresponding author. Tel.: 313-577-1245; fax: 313-745-4216. E-mail address: Rlewis@med.wayne.edu (Richard A. Lewis) of these findings are heightened in patients with ALS,