Seasonality of Atherosclerotic Cardiovascular Disease: Role of Natural and Anthropogenic Factors

The incidence and severity of exacerbation of atherosclerotic cardiovascular diseaseCardiovascular diseases (ASCVD) is greater during late autumn and winter, compared to warm season. The winter trend was shown to be characteristic of the monthly incidence of almost all major clinical entities, related to atherosclerosisAtherosclerosis. Both natural and anthropogenic factors underlying that phenomenon are discussed. The chapter describes various intermingled mechanistic concepts explaining the pathophysiology of seasonal changes in course and prevalence of cardiovascular pathology. Among them seasonal changes in lipid metabolismLipid metabolism with winter increase in cholesterolCholesterol and LDL levels. The authors discuss literature and their original data on the relation between seasonal changes of lipoprotein spectrum and parameters of immune system. Because thyroid functionThyroid function has deep impact on lipid metabolismLipid metabolism and cardiovascular regulation, the seasonalitySeasonality of thyroid activity is discussed in detail in relation to winter trend of cardiovascular disorders. The findings of the original studies of thyroid seasonality in relation to lipid metabolismLipid metabolism changes are reviewed. The seasonal changes of thyroid activity may alter the metabolic and physiological parameters essential for rates of atherogenesisAtherogenesis and complications of atherosclerosisAtherosclerosis, both in healthy people and in cardiovascular or thyroid patients. The mechanisms of this relation are numerous, not only relying upon air temperature changes, but also depending on photoperiodism. Perhaps, seasonal air humidityAir humidity and atmospheric pressureAtmospheric pressure characteristics as well as seasonal frequency and magnitude of electromagnetic phenomena may contribute. Thyroid hormones act on permissive background of other hormonal and immune influences, which makes annual interplay of ASCVD and thyroid status even more complicated and multi-faceted. It is demonstrated that unlike rapid short-time reactions, the prolonged seasonal fluctuations of thyroid activity mostly depend on photoperiodic changes, and not on air temperature. The difference in thyroid-depending seasonalitySeasonality in polar areas and middle latitudes is discussed. The data emphasizing the roles of pineal gland, macro-TSH, prolactin and immune effectors in seasonal changes of thyroid functionThyroid function are included. Special section of the chapter is devoted to the role of magnetosphereMagnetosphere and cosmo-terrestrial influencesCosmo-terrestrial influences in seasonality of ASCVD. The impacts of the fluctuations of geomagnetic activity, solar activity and cosmic rays are discussed, including intensity of neutrons/space proton flux activeness. The influence of lunar periodism is briefly discussed, as well as classical and newest concepts explaining the mechanisms of these phenomena. Some seasonal effects on cardiovascular morbidity and mortality are mediated via seasonality of infectionsInfections and seasonal changes of microorganisms, which is also discussed in details regarding some pathogens able to influence atherogenesisAtherogenesis. Seasonal non-thyroid hormonal changes altering cardiovascular reactivity were also briefly reviewed, as well as the role of natural disasters and weatherWeather anomalies. The final section of the chapter describes various anthropogenic factors partially responsible for ASCVD seasonality (air pollutionAir pollution with special attention paid to particulate matterParticulate matter, industrial electromagnetic smog, radionuclides, and various man-made stressors). The mechanisms of their action, their impact on seasonalitySeasonality of cardiovascular pathology as well as their interaction with natural factorsNatural factors are discussed.