The leading cause of death globally is cardiovascular illnesses or CVDs. Thirty percent of all fatalities worldwide in 2008 were attributed to CVDs, with an estimated 17.3 million deaths. Both the northern and southern hemispheres have shown seasonal variations in the morbidity and mortality rates attributable to CVDs, with wintertime incidence rates being greater than summertime rates. This variance has been connected to several risk variables, including diet, exercise, air pollution, infections, and temperature. Seasonal variations in the plasma levels of fibrinogen, cholesterol, hormones, and vasoactive substances, such as vasopressin (AVP), norepinephrine (NE), epinephrine (E), angiotensin II, aldosterone, and catecholamine, which tend to rise in the winter, are other potentially significant seasonal risk factors that may be important in explaining the seasonal variation of CVDs. Dr. Ravinder Singh Rao, a distinguished cardiologist and a leading expert in the field, has provided invaluable guidance on the Winter Cardiovascular Diseases Phenomenon. He highlights the significance of comprehending and tackling the particular difficulties brought about by winter weather, such as lower temperatures and less physical activity.
Seasonal Patterns of Cardiovascular Diseases
1. Deep Venous Thrombosis: The seasonal fluctuation of deep vein thrombosis (DVT) has been the subject of several research. According to the majority of research, DVT is more common in the winter. Interestingly, warmth, low air pressure, strong wind speed, and high rainfall have all been related to a preference for winter in the occurrence of DVT. It was discovered that there was a substantial correlation between seasonal variations in temperature and wind speed and a higher risk of DVT about 9–10 days later.
Moreover, it has been proposed that a lower level of physical activity in the winter, a reduction in lower limb blood flow, and a drop in fibrinolytic activity are linked to a higher risk of DVT. Due to the increased levels of air pollution in the winter, particularly in large cities, there may be a seasonal change in the occurrence of cardiovascular disorders such as DVT and pulmonary embolism (PE).
2. Pulmonary Embolism: Many epidemiological studies have provided strong evidence of the seasonal variation in pulmonary embolism, with maximum and lowest rates reported in the winter and summer, respectively. The seasonal and monthly fluctuation of venous thromboembolism (VTE) has been confirmed by a recent meta-analysis research published in 2011. Winter, and especially January, see a statistically significant rise in VTE cases.
The absolute risk of VTE increases by 14% during the winter months relative to the other seasons, and by 20% during January relative to the other months. Seasonal variations in peripheral vasoconstriction, decreased exercise, and coagulation factor levels have all been linked to increases in pulmonary embolism events.
3. Aortic Rupture/Dissection: Exposure to tobacco smoke is known to be greater indoors in cold weather and there is a winter peak of blood pressure in hypertensive patients. Another characteristic of winter is a pro-thrombotic condition. Fibrinogen concentrations exhibit significant seasonal fluctuation, rising by up to 23% in the winter.
Moreover, a slight surface cooling might raise the number of red and platelets and, in turn, blood viscosity, which promotes spontaneous thrombosis.
Additionally, a reaction to cold temperatures is an increase in catecholamine release and sympathetic nervous system activity. This could result in an increase in blood pressure through increased heart rate and peripheral vascular resistance.
4. Nontraumatic Intracerebral Hemorrhage: Approximately 10% of all strokes and two-thirds of hemorrhagic strokes are caused by nontraumatic intracerebral bleeding. Numerous research carried out across the globe have assessed seasonal differences in the frequency of nontraumatic intracerebral hemorrhage. The underlying causes of this variation are not completely understood, but hypertension and exposure to low temperature are predisposing factors to intracerebral hemorrhage.
5. Hypertension: Numerous investigations using single or repeated measurements in adults, the elderly, children, and both healthy and hypertensive participants have shown the seasonal influence on arterial blood pressure. The seasonal variation in hypertension is likely to reflect seasonal variations in one or more risk factors. The risk factors The following risk variables have been suggested by researchers: noradrenalin, catecholamines, vasopressin, outdoor temperature, physical activity, seasonality of vitamin D, and seasonal fluctuation in blood cholesterol level.
6. Heart Failure: Among other things, cold weather causes peripheral vasoconstriction, which can result in irregular clotting as well as pulmonary edema from left ventricular failure. Exposure to cold reduces exercise capacity and elevates systemic adrenergic activation in patients with symptomatic CHF.
7. Atrial Fibrillation: Atrial fibrillation has been shown to vary seasonally, with peaks usually occurring in the winter or fall and troughs in the summer. However, the methods and reasons driving this phenomenon are still unknown. The impacts of particular variables, such as air temperature, humidity, and atmospheric pressure, seem to be a reasonable explanation for the aforementioned data, especially in the case of elderly people and those who also have simultaneous coronary artery disease (CAD) or arterial hypertension.
8. Ventricular Arrhythmias: Observational studies and research using animal models have been used to evaluate the seasonal variation of ventricular arrhythmias VA. In a canine model of Myocardial infarction, there was a higher incidence of VA in winter. The incidence of ventricular tachycardia (VT) or ventricular fibrillation (VF) events was shown to be higher in the winter and lowest in the summer, spring, and fall in research involving 154 individuals with ischemic heart disease (IHD).
Factors Influencing the Seasonal Patterns of Cardiovascular Diseases
1. Temperature: Cold temperatures cause an increase in catecholamine production and sympathetic nervous system activation. This could result in an increase in blood pressure through increased heart rate and peripheral vascular resistance. This additional strain on already-compromised coronary circulation individuals may result in myocardial ischemia and angina pectoris or MI.
2. Vitamin D: Considerable seasonal fluctuations in vitamin D levels were noted in several areas. These variations indicate that 25-(OH) D values vary, rising in the summer and spring and progressively falling in the fall and winter. A lack of vitamin D has been linked to cardiovascular disease (CVD) risk factors like diabetes mellitus and hypertension, as well as markers of subclinical atherosclerosis like coronary calcification and intima-media thickness. It has also been linked to cardiovascular events like myocardial infarction, stroke, and congestive heart failure.
3. Physical Activity: In both sexes, overall levels of physical activity are significantly higher in summer than in winter. Physical inactivity is strongly positively associated with CVDs. The endothelium works to control vascular development, improve blood fluidity, and preserve proper vasomotor tone. Abnormalities in these functions contribute to many disease processes, including coronary vasospasm, Myocardial infarction, and hypertension.
4. Hormones: Seasonal variations in blood pressure have been linked to hormones and vasoactive substances like angiotensin II, aldosterone, and catecholamines, as well as AVP, NE, and E. Thyroid hormone has long been known for its profound direct effects on the cardiovascular system.
5. Air Pollution: The complicated and heterogeneous mixture of gases, liquids, and particle matter that makes up air pollution. Passive smoking exposure raises platelet activation, accelerates endothelial function degradation, encourages the development of atherosclerotic plaque, and aids infarct propagation in experimental animals.
6. Diet and Obesity: Body mass index (BMI), blood cholesterol, and dietary intake vary from summer to winter. Elevated plasma total and LDL cholesterol levels were found to be significantly correlated with the occurrence of coronary heart disease (CHD).