Environmental Determinants of Cardiovascular Disease

Abstract

Many features of the environment have been found to exert an important influence on cardiovascular disease (CVD) risk, progression, and severity. Changes in the environment because of migration to different geographic locations, modifications in lifestyle choices, and shifts in social policies and cultural practices alter CVD risk, even in the absence of genetic changes. Nevertheless, the cumulative impact of the environment on CVD risk has been difficult to assess and the mechanisms by which some environment factors influence CVD remain obscure. Human environments are complex, and their natural, social, and personal domains are highly variable because of diversity in human ecosystems, evolutionary histories, social structures, and individual choices. Accumulating evidence supports the notion that ecological features such as the diurnal cycles of light and day, sunlight exposure, seasons, and geographic characteristics of the natural environment such as altitude, latitude, and greenspaces are important determinants of cardiovascular health and CVD risk. In highly developed societies, the influence of the natural environment is moderated by the physical characteristics of the social environments such as the built environment and pollution, as well as by socioeconomic status and social networks. These attributes of the social environment shape lifestyle choices that significantly modify CVD risk. An understanding of how different domains of the environment, individually and collectively, affect CVD risk could lead to a better appraisal of CVD and aid in the development of new preventive and therapeutic strategies to limit the increasingly high global burden of heart disease and stroke.

Keywords: air pollution; altitude; circadian rhythm; coronary artery disease; diet; exercise; smoking; social class; social support; stroke; sunlight.

Figure 1

The human envirome. The human environment is categorized into natural, social and personal domains. The natural domain of the environment is characterized both by natural ecology and geology, as well as the diurnal cycles, seasons and greenspaces. The influence of the natural environment is moderated both by the physical attributes of the social environment as well as social and networks and socioeconomic status of the individual within society. Features of social environments, such as pollution and occupation also affect CVD risk. The social environment, permits, promotes, facilitates or constrains lifestyle choices such as physical activity, nutritional choices and smoking that constitute important domains of the personal environment. Collective influences of these nested domains of the environment have been found to profound influence CVD risk, incidence, prevalence and severity.

Figure 2

The effect of sunlight on cardiovascular health. The visible range of sunlight regulates the master clock located in the pacemaker neurons of the suprachiasmatic nucleus, which sets the intrinsic 24 h cycle and synchronizes the light-insensitive peripheral clocks to coordinate cycles of waking, sleeping and feeding. The UVB radiation converts 7-dehydrocholesterol in the epidermis to previtamin D3, which undergoes thermal isomerization to vitamin D. Vitamin D3 formed in the skin appear in the circulation and is then transported to the liver where it is converted to 25(OH)D3. In kidney, 25(OH) D3 undergoes hydroxylation to form biologically active 1,25(OH)2D. The UVA radiation induces the photo-degradation of nitrosothiols, such as S-nitrosylglutathione, which leads to the generation of NO, an important regulator of blood pressure.

Figure 3

Data from the World Health Organization showing cause-specific deaths attributable to the environment per year worldwide.