Residual environmental risk in patients with cardiovascular disease: an overlooked paradigm

Abstract

Despite advances in therapeutics and implementing what is already known, patients with cardiovascular disease (CVD) remain at high risk for adverse health outcomes. The term ‘residual risk’ is often used to succinctly convey lingering cardiovascular risk even after optimal treatment of risk factors. In recent years, there has been a focus on understanding residual thrombotic and residual inflammatory risks1 to improve CVD outcomes. Environmental exposures, particularly air pollution, have been causally linked with the development and progression of CVD, leading to elevated risks for adverse events including mortality.2 Particulate matter air pollution alone is responsible for ∼9 million annual deaths globally.2 Robust evidence from animal and human studies has elucidated the mechanisms of air pollution–induced cardiovascular effects, which are partially mediated through haemodynamic, inflammatory, and thrombotic factors.2 Patients with pre-existing CVD and risk factors are more susceptible to the adverse effects of air pollutants. For example, each 10 µg/m3 increase in ambient particulate matter air pollution exposure is associated with a 26% increase in major adverse cardiovascular events in patients with coronary artery disease undergoing percutaneous coronary intervention, independent of clinical factors.3 Moreover, additional environmental exposures, such as gaseous pollutants, noise, nocturnal light, and other factors of the built environment, have also been linked with poor outcomes.2 Paralleling the concepts of residual inflammatory and thrombotic risks in patients with CVD, we introduce the concept of ‘residual environmental risk’, which refers to the contribution of all environmental factors to continuing cardiovascular risk after all traditional risk factors have been addressed. In other words, it is the sum totality of risk that cannot be attributed to conventional risk factors, such as hypertension, diabetes, and smoking, but rather to other major environmental factors that are otherwise completely overlooked. Ongoing exposure to pervasive environmental risk factors, such as air pollution and noise, may contribute to substantial residual risk, highlighting the need for targeted interventions to address these factors in addition to traditional risk factors. Addressing residual CVD risk comprehensively may require a re-examination of risk as currently perceived by health care professionals. Many environmental factors such as air pollution are not in the radar of physicians, despite their acknowledgement by multiple cardiovascular societies that these factors often pose the same if not higher risk than many traditional risk factors to cardiovascular health and despite mounting evidence that lowering exposures to risk factors such as toxic metals and air pollution may provide substantial health benefits.2 Reducing exposure to environmental hazards may also require health care professionals to be more prescient in identifying and targeting susceptible groups. At a societal level, regulatory actions towards more stringent air quality standards, as well as clean-up programmes and restrictions on harmful chemicals and toxic metals, are massively important.2 Reducing exposures may also involve better education and promotion of patient-level interventions, such as lifestyle modifications that reduce exposure to environmental hazards, including avoidance of outdoor activities during times of high air pollution. More strict management of traditional risk factors may also be of particulate benefit and essential for individuals at high residual environmental risk. For example, we have shown that intensive blood pressure lowering (<120/80 mmHg) in patients with hypertension is associated with reduced cardiovascular risk in individuals exposed to higher levels of air pollution in the USA, possibly to a higher degree compared with patients exposed to lower levels of air pollution.4 Studies have also shown that personal strategies to reduce air pollution exposure, such as masks and portable air cleaners, are effective in improving CVD parameters (e.g. blood pressure and inflammation). Efforts to address residual CVD risk should also consider the role of the social ‘environment’ and the residual risk conveyed by poorly appreciated social determinants of health. Addressing social determinants of health, such as access to health care, food insecurity, transportation, and social support, may therefore also be critical. Environmental hazards such as air, noise, and light pollution in addition to aspects in the built environment such as poor tree cover are often also more prevalent in marginalized communities, reflecting critical observations of environmental injustice.5 Given the extent and scale of the confluence of environmental and social risk factors, long-term sustainable strategies may require a radical transformation of the design of entire communities. The concept of residual environmental CVD risk, therefore, entails the careful consideration of often ‘invisible’ environmental factors that may contribute to risk, even after traditional risk factors have been addressed. Addressing this may require sophisticated approaches that take into account a myriad of factors in the natural, built, and social environments. To this end, a data science–driven framework, to sift through complex, non-linear, multi-sector exposures, facilitating deconstruction of environmental health risks may be warranted towards paving the way for efficient policy portfolios that balance economic, social, and environmental goals. Re-examining the residual risk paradigm (Figure 1) to include social and environmental factors may help shine a light on pervasive inequities in society and accelerate sustainable development goals. An updated paradigm for residual risk in patients with cardiovascular disease. This figure illustrates a paradigm for residual risk in patients with cardiovascular disease. Central traditional risk factors, with additional inclusion of residual thrombotic and inflammatory risks that are well-known contributors to cardiovascular disease risk. However, there is a growing recognition of the importance of social and environmental risk factors in driving residual risk, emphasizing the need for a comprehensive approach to risk assessment and management. All authors declare no conflict of interest for this contribution. This study was funded by the National Institute of Health Awards P50MD017351 and R35ES031702.

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