The severity of obstructive sleep apnoea does not influence ambient IGF‐I levels

Objective Obstructive sleep apnoea (OSA) is reported to have effects on a number of hormone systems including the hypothalamo‐pituitary axis. We aimed to determine the impact of OSA severity on insulin‐like growth factor‐I (IGF‐I) levels. Design and Methods This is a prospective cohort study performed between November 2014 and May 2017. IGF‐I was measured on serum samples, and data were collected on demographics, BMI and parameters of OSA. Results 611 participants were recruited (202 female, 53.5 ± 12.5 years; mean BMI 36.2 ± 8.0 kg/m2). 26.2% had mild OSA; 27.3%, moderate OSA; and 44.5%, severe OSA. 15.2% of IGF‐I values were below the age‐related reference range. Increasing BMI correlated with greater AHI (r = .28, p < .001), ODI (r = .30, p < .001), severity of OSA (r = .17, p < .001), duration with oxygen saturation (SaO2) <90% (r = .29, p = .001) and reduced median SaO2 levels (r = .19, p < .001). IGF‐I levels correlated negatively with age (r = −.13, p = .001), BMI (r = −.16, p < .001), diabetes (r = −.108, p = .009), AHI (r = ‐0.10, p = .043) and severity of OSA (r = −.10, p = .013). No association of IGF‐I was observed with ODI, median SaO2 levels or duration of SaO2 < 90%. Regression analyses were used to examine determinants of IGF‐I, all of which contained the independent variables of age, gender and BMI. All models showed IGF‐I to be predicted by age and BMI (p < .05); however, none of the parameters of OSA were significant within these models. Conclusion Insulin‐like growth factor‐I levels in OSA are dependent on age and BMI; however, no additional effect of any OSA parameter was observed, supporting the hypothesis that OSA effects on IGF‐I are indirect through concomitant body composition and metabolic parameters.