Impact of noise and air pollution on the cardiovascular system through the brain–heart axis

Noncommunicable diseases such as cardiovascular disease (CVD) are becoming more prevalent in urbanized and industrialized societies. Classic risk factors such as hypertension are reinforced by behavioral factors such as smoking and diet, and environmental risk factors such as transportation noise and air pollution. Animal studies reveal that noise causes annoyance and sleep disturbance, promoting stress hormone release. Air pollution damages the lung, causing inflammation and oxidative stress that can spread to the circulation and remote organs. Both noise and air pollution converge at the vascular level, causing dysfunction in vascular signaling and atherosclerotic plaque formation. The complex interplay between environmental risk factors and CVD can lead to synergistic health impacts. The present review focusses on the impact of noise and air pollution on the brain–heart axis. Noise causes its primary health effects on the brain by activating the sympathetic nervous system and the hypothalamic–pituitary–adrenal axis and thereby causes neuroinflammation, cerebral oxidative stress and via stress hormone signaling, and also induces cardiovascular damage. Air pollution activates the stress response as a homeostatic stressor. Uptake of (nano)particles into the brain can proceed by migration along the olfactory nerve. Particles in the brain can cause stress responses similar to neuroinflammation and cerebral oxidative stress due to noise. Understanding the negative effects of noise and air pollution on the cardiovascular system could help protect patients with preexisting CVD.