Obstructive sleep apnoea syndrome impairs insulin sensitivity independently of anthropometric variables.
OBJECTIVE
Obstructive sleep apnoea syndrome (OSAS) is strongly associated with obesity and characterized by endocrine and metabolic changes including impairment of insulin sensitivity. The aim of this study was to further clarify the insulin dynamics and glucose metabolism in this condition.


METHODS
We studied 30 obese patients with OSAS [OSA, 21 males, 9 females; age, mean +/- SEM: 53.1 +/- 1.7 years; body mass index (BMI): 38.6 +/- 1.1 kg/m2; waist-to-hip ratio (WHR): 0.99 +/- 0.07; Apnoea/Hypopnoea Index (AHI): 40.5 +/- 5.8 events/h of sleep] by means of overnight polysomnography and oral glucose tolerance testing. Mathematical models were used to assess: (i) whole-body insulin sensitivity index (ISI composite); (ii) hepatic ISI; (iii) the first phase of insulin secretion (DeltaI30'-0'/DeltaG30'-0'). Results were compared with those in 27 weight-matched patients with simple obesity (OB, 12 males, 15 females; age: 48.1 +/- 2.8 years, BMI: 38.5 +/- 1.4 kg/m2, WHR: 0.94 +/- 0.09; AHI: 2.15 +/- 0.5 events/h of sleep) and with 20 normal subjects (NS, 15 females; 5 males, age: 40.4 +/- 2.9 years; BMI: 22.2 +/- 0.6 kg/m2).


RESULTS
ISI composite value was significantly lower in OSAS (1.71 +/- 1.41) than in OB (3.08 +/- 0.27) and in NS (6.1 +/- 0.4) even after age-, BMI- and WHR-adjustment. Similarly, hepatic ISI was significantly different among the three groups (OB = 0.25 +/- 0.02, OSAS = 0.16 +/- 0.014 and NS = 0.55 +/- 0.04). Sex did not affect ISI indices. Insulin secretion estimates were not significantly different among the three groups.


CONCLUSIONS
Obese patients with obstructive sleep apnoea syndrome are more insulin resistant than patients with simple obesity independently of the degree and distribution of adiposity. The worsening in insulin sensitivity in obstructive sleep apnoea syndrome patients could reflect the hypoxic state and would account for the increased vascular risk in this condition.
Tassone
Francesco
F
Division of Endocrinology, Department of Internal Medicine, University of Turin, Italy.
Lanfranco
Fabio
F
Gianotti
Laura
L
Pivetti
Sonia
S
Navone
Fabrizia
F
Rossetto
Ruth
R
Grottoli
Silvia
S
Gai
Valerio
V
Ghigo
Ezio
E
Maccario
Mauro
M
D000704:Analysis of Variance; D001786:Blood Glucose / Q000032:analysis; D001824:Body Constitution; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D017286:Polysomnography; D012891:Sleep Apnea Syndromes / Q000378:metabolism*
D001786:Blood Glucose; D007328:Insulin