Obesity hypoventilation syndrome (OHS) is often diagnosed late. The aim of this study was to analyse gender differences at initiation of long-term mechanical ventilation (LTMV) in patients with (OHS), to analyse gender differences in treatment effect and to study how the prescription of LTMV due to OHS has changed over time.

Data on patients on LTMV due to OHS between 1996 and 2014 were obtained from Swedevox, a nationwide health quality registry of patients on LTMV in Sweden.

When starting LTMV, women were generally older (age 64.4 ± 11.2 vs. 60.1 ± 12.1 years, p < 0.001), more obese (BMI 43.0 ± 8.2 vs. 41.5 ± 7.9 kg/m2, p < 0.001), more hypoxic (PaO2 7.6 ± 1.5 vs. 7.9 ± 1.6 kPa, p = 0.001), had more hypercapnia (PaCO2 7.2 ± 1.3 vs. 6.9 ± 1.3 kPa, p = 0.001), had higher base excess (6.9 ± 4.1 vs. 5.8 ± 4.7 kPa, p < 0.001) and more frequently started LTMV in a non-elective situation (43.2% vs. 37.5%, p = 0.026) than men. Improvement of arterial blood gas values or in age-adjusted mortality at one-year follow-up did not differ. During the study period, the age of patients at the initiation of LTMV rose by 3.4 years/decade (P = 0.001) in women and with 1.9 years/decade (P = 0.048) in men but there were no significant changes in BMI (P = 0.425).

Diagnosis of OHS is more delayed in women and as a consequence the disease is more advanced when diagnosed. In spite of this, there is no gender difference in survival rate in patients with OHS treated with LTMV. More and older patients with OHS nowadays gain access to LTMV.