Prevalence and risk factors of syndrome Z in urban Indians.

BACKGROUND: Syndrome Z is defined as the co-occurrence of obstructive sleep apnea (OSA) and metabolic syndrome. There is a paucity of information on the magnitude of syndrome Z in the community and the factors associated with it. METHODS: We conducted a two-stage, cross-sectional, community-based study in four different socioeconomic zones of the South Delhi district, India, from April 2005 through June 2007. In stage 1, a systematic random sample of subjects of either gender aged 30-65 years were administered a questionnaire by door-to-door survey. Subjects that responded were classified as habitual and non-habitual snorers. In stage 2, all the habitual and 10% of randomly selected non-habitual snorers were invited for overnight polysomnography and evaluation for metabolic syndrome. The National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATPIII) criteria were used to define metabolic syndrome. RESULTS: Of the 2860 subjects approached, 2505 (88%) completed stage 1; 452 (18%) were habitual snorers. In stage 2, OSA (defined as apnea-hypopnea index > or =5) was observed in 94 (32.4%) of 290 habitual snorers and 3 (4%) of 75 non-habitual snorers. Seventy (77%) of the 91 habitual snorers with OSA also had metabolic syndrome; none of the non-habitual snorers with OSA had metabolic syndrome. The estimated population prevalence of metabolic syndrome was 43% [95% CI: (41.0-44.9%)] and syndrome Z was 4.5% (95% CI: 3.7-5.3). On multivariable analysis, age [OR: 1.05 (1.00-1.09)], male gender [OR: 5.64 (2.06-15.49)], percent body fat [OR: 1.08 (1.04-1.13)] and DeltaSaO(2) (%) (defined as the difference between baseline and minimum SaO(2) during overnight sleep study) [OR: 5.80 (2.36-14.26), 17.70 (5.97-52.17) and 57.1 (19.12-170.40) for 10-20%, 20-30% and >30% reduction respectively as compared to <10% reduction] were independently associated with syndrome Z. CONCLUSIONS: To the best of our knowledge, this is the first population-based study on the prevalence and risk factors of syndrome Z, and it reveals that a considerable proportion of community-dwelling northern Indian adults have syndrome Z. Age, male gender, percent body fat and severity of nocturnal desaturation were independent risk factors for syndrome Z.

Prevalence and risk factors of obstructive sleep apnea among middle-aged urban Indians: a community-based study.

BACKGROUND: The epidemiology of obstructive sleep apnea (OSA) and obstructive sleep apnea syndrome (OSAS) is not well studied among Indians. We sought to determine the prevalence and risk factors of OSA in a middle-aged urban Indian population. METHODS: We conducted a two-stage, cross-sectional, community-based study in four different socioeconomic zones of the South Delhi district, India, from April 2005 to June 2007. In stage 1, subjects of either gender aged 30-65 yrs were administered a questionnaire by door-to-door survey using systematic random sampling. Subjects that responded were classified as habitual and non-habitual snorers. In stage 2, all the habitual and 10% of randomly selected non-habitual snorers were invited for overnight polysomnographic study. RESULTS: Of the 2860 subjects approached, 2505 (88%) completed stage 1. Habitual snoring was present in 452 (18%) subjects. In stage 2, OSA defined as apnea-hypopnea index 5 was observed in 94 (32.4%) of 290 habitual snorers and 3 (4%) of 75 non-habitual snorers. Estimated population prevalence of OSA and OSAS was 9.3% (95% CI 8.2-10.5%) and 2.8% (2.1-3.4%) respectively. On multivariable analysis, male gender (adjusted odds ratio 3.8 [1.7-4.9]), body-mass index 25 kg/m(2) (4.1 [2.0-8.3]), and abdominal obesity (2.2 [1.9-5.3]) were independently associated with the presence of OSA. A linear trend was observed in the prevalence of OSA across the socioeconomic strata. CONCLUSIONS: OSA is a significant public health problem in the middle-aged Indian population across the socioeconomic spectrum. OSA is associated with some of the well known risk factors for cardiovascular disease.