Idiopathic pulmonary fibrosis and sleep disorders: no longer strangers in the night

TABLE 1

Sleep in idiopathic pulmonary fibrosis

Sleep macro- and micro-architecture	Increased stage 1 sleep Decreased REM and slow-wave sleep Decreased sleep efficiency Increased WASO Increased arousal index
Respiratory pattern	Increased respiratory frequency during sleep Rapid and shallow breathing (especially during REM sleep)
Nocturnal oxygenation parameters	Episodic desaturation during REM sleep Desaturation during NREM sleep Desaturation due to respiratory events (apnoeas and hypopnoeas)
Sleep disordered breathing	Increased incidence of obstructive sleep apnoea
Other sleep problems	Increased periodic leg movements during sleep Insomnia Nocturnal cough

TABLE 2

Biomarkers in idiopathic pulmonary fibrosis

Diagnostic biomarkers	KL-6 [81] SP-A and SP-D [81] YKL-40 [81] MMP-1 and MMP-7 [81] CXCL13 [82]
Disease susceptibility biomarkers	Telomerase genes [83–85] Telomere length [86] MUC5B [87, 88] TOLLIP–SPPL2C [89]
Prognostic biomarkers	KL-6 [81] CCL-18 [90] YKL-40 [81] Circulating fibrocytes [91] CD28 [92] CD28/ICOS/Lck/ITK [77] MMP-7/ICAM-1/IL-8/VCAM-1/S100A12 [78] MUC5B [93] Cilium-associated genes [94] Antibodies against periplakin [95] Antibodies against HSP-70 [96] LOXL2 [97] CXCL13 [82] TLR-3 [98]

SP: surfactant protein; MMP: matrix metalloproteinase; MUC: mucin; TOLLIP: Toll-interacting protein; SPPL: signal peptide peptidase-like; CD: cluster of differentiation; ICOS: inducible T-cell costimulatory; Lck: lymphocyte-specific protein tyrosine kinase; ITK: interleukin-2-inducible T-cell kinase; ICAM: intercellular adhesion molecule; IL: interleukin; VCAM: vascular cell adhesion molecule; HSP: heat shock protein; LOXL: lysyl oxidase-like; TLR: Toll-like receptor.

TABLE 3

Biomarkers in obstructive sleep apnoea

Inflammatory markers (CRP, IL-6, TNF-α, fibrinogen, CCL-18)

Systemic hypertension

Carotid intimal–medial thickness

Metabolic markers (HbA1c)

Markers of oxidative stress (8-isoprostane, IL-6, nitric oxide)

Others (cysteine)