BMC Public Health 2009, 9:130 http://www.biomedcentral.com/1471-2458/9/130 After stratifying the analyses by gender and region simul- taneously (Table 4), the effect of SRH, presence of depres- sive symptoms and sleep duration remained significant among all subgroups. Marital status, social activity, pros- tatism and residential status significantly affected Shang- hai men and CVD significantly affected Beijing men and Shanghai women. Sleep quality and cardio-metabolic biomarkers Significant differences in the level of resistin, PAI-1, insu- lin, HOMA-IR, HOMA2-IR, LDL, TCH and TG were observed between different levels of sleep quality (Table 5). When we analyzed these associations among a sub- sample of the population who were free from CVD and diabetes, we found that significant associations remained for insulin, HOMA-IR, HOMA2-IR, LDL, TCH and TG (data not shown). Discussion Only half of middle aged and elderly Chinese in our study reported good sleep quality. Quality of sleep varied sub- stantially by gender and geographical location and was affected by level of self-rated health, presence of depres- sive symptoms, sleep quantity, chronic diseases and social activity. Significant associations between levels of sleep quality and resistin, PAI-1, insulin, HOMA-IR, HOMA2- IR, LDL, TCH and TG were observed. These associations remained significant for insulin, HOMA-IR, HOMA2-IR, LDL and TCH among a subgroup of participants who were free of CVD and diabetes. Sixteen percent of the elderly Chinese assessed their sleep quality as poor in this study. They showed higher preva- lence of mental and physical diseases (depression, CVD, arthritis, prostatism (men only)) and shorter daily sleep time compared to participants that reported a good level Table 4: Adjusted associated factors of sleep quality stratified by region and gender Association with sleep quality (OR with 95% CI) Beijing-Male Shanghai-Male Beijing-Female Shanghai-Female 1.50 (0.92–2.45) 3.90 (2.06–7.39)* Variable Residential location (rural vs. urban) Body Mass Index (BMI) normal vs. over weight under weight vs. over weight Smoking current vs. never smoker former vs. never smoker Alcohol drinking (no vs. yes) Physical activity high vs. low moderate vs. low Educational level, years in school ‡ group 1 vs. 3 group 2 vs. 3 Marital status (no spouse vs. spouse) Medical insurance (no vs. yes) Employment employed vs. retired unemployed vs. retired Social activity (no vs. yes) Self rated health status (good vs. not good) Diabetes (no vs. yes) CVD (no vs. yes) Arthritis (no vs. yes) Prostatism (no vs. yes) Depressive Symptoms (no vs. yes) Total hours of sleep/day <7 vs. 9< hrs 7–9 vs. 9< hrs 1.03 (0.73–1.47) 0.21 (0.08–0.57)* 0.81 (0.52–1.27) 1.16 (0.69–1.95) 0.84 (0.59–1.19) 0.99 (0.50–1.98) 0.70 (0.34–1.42) 1.70 (0.98–2.96) 1.05 (0.68–1.62) 1.12 (0.64–1.96) 0.67 (0.42–1.09) 0.82 (0.55–1.23) 0.77 (0.46–1.27) 0.86 (0.60–1.22) 2.18 (1.51–3.16)* 1.05 (0.68–1.61) 1.78 (1.12–2.83)* 1.74 (0.96–3.15) 1.17 (0.69–1.99) 3.13 (1.82–5.38)* * 0.12 (0.06–0.23)* 0.66 (0.37–1.16) 0.77 (0.53–1.11) 1.27 (0.47–3.48) 0.96 (0.62–1.48) 0.63 (0.36–1.08) 0.86 (0.58–1.26) 2.09 (1.02–4.30)* 1.57 (0.75–3.31) 0.74 (0.37–1.50) 0.82 (0.50–1.35) 4.87 (2.12–11.19)* 0.75 (0.44–1.28) 1.10 (0.71–1.70) 1.29 (0.75–2.19) 0.64 (0.44–0.93)* 3.11 (2.00–4.83)* 0.78 (0.45–1.34) 1.58 (0.85–2.96) 0.56 (0.29–1.09) 1.72 (1.00–2.97)* 9.06 (3.50–23.49)* * 0.11 (0.04–0.29)* 0.61 (0.23–1.62) 0.68 (0.41–1.14) 0.98 (0.73–1.32) 0.42 (0.14–1.28) 0.75 (0.47–1.22) 1.06 (0.52–2.18) 1.20 (0.81–1.77) 0.77 (0.46–1.30) 0.77 (0.45–1.32) 1.26 (0.79–1.99) 1.18 (0.78–1.81) 1.30 (0.89–1.89) 1.06 (0.66–1.71) 1.34 (0.86–2.11) 0.96 (0.64–1.44) 0.82 (0.61–1.10) 2.36 (1.68–3.31)* 1.15 (0.80–1.65) 0.82 (0.53–1.25) 1.35 (0.94–1.94) 4.34 (2.95–6.36)* * 0.08 (0.04–0.14)* 0.64 (0.39–1.06) 0.86 (0.51–1.45) 0.79 (0.60–1.05) 0.91 (0.46–1.79) 0.80 (0.24–2.66) 0.17 (0.01–2.75) 0.88 (0.44–1.75) 0.98 (0.55–1.75) 0.83 (0.45–1.50) 0.91 (0.54–1.52) 0.82 (0.55–1.22) 1.08 (0.72–1.62) 0.75 (0.48–1.16) 0.93 (0.62–1.41) 1.68 (1.05–2.68)* 0.99 (0.74–1.33) 2.43 (1.75–3.39)* 1.11 (0.66–1.86) 2.72 (1.47–5.04)* 1.31 (0.89–1.93) 3.44 (1.77–6.66)* * 0.08 (0.04–0.16)* 0.45 (0.22–0.90)* Abbreviations: CES-D, Center for Epidemiologic Studies Depression Scale; CVD, Cardio-Vascular Disease; OR, Odds ratio; CI, Confidence interval. *P < 0.05. ‡ Group 1, 2 and 3 for educational level are 0–6, 7–9 and ≥10 years in school respectively. Page 7 of 11 (page number not for citation purposes)