In the 1996 National Prevalence Survey of Smoking Pattern in mainland China, the prevalence of smoking was 66.9% in men and 4.2% in women; overall, 53.5% reported passive smoke exposure. More than 72% of all Chinese (>600 million people) are regularly exposed to either active smoking or secondhand smoke (SHS). As the world's largest producer and consumer of tobacco products, China bears a substantial burden of smoking-related diseases and deaths. It is estimated that tobacco-related deaths will reach 7 million worldwide in 2025, with 2 million of these deaths predicted to occur in China. Tobacco smoking is a major risk factor for cardiovascular disease (CVD) and type 2 diabetes. Moreover, there is strong evidence that passive smoking or SHS is causally associated with coronary heart disease (CHD) and may be linked to stroke.

The metabolic syndrome (MetS) is characterized by a clustering of cardiovascular risk factors, including abdominal obesity, high blood pressure, increased glucose level, and dyslipidemia. The MetS is associated with the development of diabetes and CVD as well as an increased risk of CVD and all-cause mortality. In China, it has become an important public health problem with the prevalence of MetS being 13.7% in the middle-aged and 46.3% in the elderly populations. There is also evidence that SHS is associated with both MetS and insulin resistance. Although SHS has been examined as a risk factor for individual CVD (CHD or stroke), it has not been investigated together with MetS in the Chinese population. In this study, we examined in detail the individual and combined effects of active smoking, SHS, and MetS on cardiovascular risk in a population-based survey of elderly Chinese in Beijing, China.