Low and high air temperature and cardiovascular risk

Temperature extremes are one facet of global warming caused by climate change. They have a broad impact on population health globally. Due to specific individual- and area-level factors, some subgroups of the population are at particular risk. Observational data has demonstrated that the association between temperature and mortality and cardiovascular mortality is U- or J-shaped. This means that beyond an optimal temperature, both low and high temperatures increase cardiovascular risk. In addition, there is emerging epidemiological data showing that climate change-related temperature fluctuations may be particularly challenging for cardiovascular health. Biological plausibility for these observations comes from the effect of cold, heat, and temperature fluctuations on risk factors for cardiovascular disease. Shared mechanisms of heat and cold adaptation include sympathetic activation, changes in vascular tone, increased cardiac strain, and inflammatory and prothrombotic stimuli. The confluence of these mechanisms can result in demand ischemia and/or atherosclerotic plaque rupture. In conclusion, public health and individual-level measures should be taken to protect susceptible populations, such as patients with risk factors and/or pre-existing cardiovascular disease, from the adverse effects of non-optimal temperatures. This review aims to provide an overview of the association between temperature extremes and cardiovascular disease through the lens of pathophysiology and observational data. It also highlights some specific meteorological aspects, gives insight to the interplay of air temperature and air pollution, touches upon social dimensions of climate change, and tries to give a brief outlook into what to expect from the future.