Pattern of Sleep Disordered Breathing in Obese Indians

Obesity has become a major health problem worldwide due to high co-morbidity and an increasing prevalence. It is the greatest risk factor for obstructive sleep apnea (OSA). Owing to lack of data on the association of obesity and OSA within the country, the present study was designed to evaluate the pattern of sleep disordered breathing (SDB) among obese Indian subjects.

The study was prospectively carried out in Sleep Laboratory of LRS Institute of Tuberculosis and Respiratory Diseases, New Delhi. 30 obese [having body mass index BMI > 27.5 kg/m²] and 10 non-obese (having BMI < 27.5 kg/m²) subjects were consecutively enrolled into the study (obesity) and the control (non-obese) groups respectively as per the World Health Organization (WHO) Criteria of Obesity for Asians. Detailed clinical history including that of sleep was taken, a physical examination along with anthropometric measurements like neck circumference (NC), waist circumference (WC) and hip circumference (HC) was done and laboratory investigations were performed in all subjects, who thereafter, underwent an overnight polysomnography (PSG) on Compumedics E-Series sleep software. Sleep was staged as per Rechtshaffen and Kales (R & K) rules and SDB evaluated as per standard criteria. Data was subjected to statistical analysis.

There were 16 obese, 8 severely obese & 6 morbidly obese subjects. Respective characteristics of the obesity and the control group subjects showed a mean age of 47.73 and 40.90 years, a male-female ratio of 19: 11 and 7:3, and a mean BMI of 33.46 and 23.73 kg/m². Mean Apnoea-Hypopnoea Index (AHI) was significantly higher among the subjects of the obesity group as compared to the controls. Similarly, mean AHI was significantly higher among the obese males, those having NC between 35 to < 45 cms, symptomatics, those having 4 to 6 number of symptoms, and those having co-morbidities as compared to the respective non-obese counterparts. Mean value of sleep latency was higher, while that of Total Sleep Time (TST) & sleep efficiency lower in the obesity than the control group. Oxygen De-saturation Index (ODI) and indices of arousal, Periodic Limb Movement (PLM) in Sleep (PLMS) & PLM with arousals were significantly higher in the obesity as compared to the control group respectively. No significant differences were noticed between the groups with regard to sleep stage percentages.

SDB was present in 86.6% (26/30) of obesity subjects, of whom 80% (24/30) had mild, moderate and severe OSA (with 2/3^rd having moderate to severe OSA and more than half having severe OSA), and 6.6% (2/30) had Upper Airway Resistance Syndrome (UARS) or Respiratory Effort Related Arousal (RERA). Obesity Hypoventilation Syndrome (OHS) co-existed in 37.5% (9/24) of subjects with OSA constituting one-third of total cases. PLMS co-existed in 7 subjects with OSA. All 6 morbidly obese subjects had some form of SDB with OSA in 5 and RERA in 1 of them.

Among the control subjects, 50% had a normal sleep study and others had only mild (40%; 4/10) and moderate OSA (10%; 1/10), while none had severe OSA. Further, OSA co-existed with PLMS in only 1 subject.

Mean AHI is higher among the subjects of obesity group as compared to non-obese subjects. Mean AHI is also higher among the obese males, those having NC between 35 to < 45 cms, symptomatics, those having 4 to 6 number of symptoms, and those having co-morbidities in comparison to the respective non-obese subjects. The obese subjects sleep for less time taking longer time to sleep, have higher number of arousals and PLMS per hour, and have greater nocturnal oxygen de-saturation (NOD) than the non-obese. OSA is present in 80% of subjects with obesity and SDB exists in all morbidly obese subjects. A need exists for all obese subjects to undergo a thorough clinical assessment with inclusion of a sleep history, a polysomnographic evaluation and an arterial blood gas analysis to detect and manage SDB early.