Introduction
In many populations, cardiovascular diseases follow a scene pattern. People living in milder climates are vulnerable to seasonality. The seasonal changes show evidence of changes in cardiovascular functioning. There are attenuated peaks of cardiovascular events during the summer and winter seasons. It can be described as winter peaks and summer troughs. Populations in the North and Southern hemisphere showed higher winter rates of cardiac events.
What Are the Factors Influencing Seasonal Variations of CVD?
Seasonal variations cause sudden rise and fall in temperatures and can affect the circulatory system and certain health parameters. The incidence of disease and mortality increases during winter seasons. In England and Wales, the winter peak results in an average of 20,000 deaths every year. The seasonal variations also change lifestyle, dietary habits, and physical activity. All these together can influence the functioning of the heart and leads to cardiovascular diseases.
Various factors can lead to changes in coronary heart disease. The incidence, survival, and mortality rate also changes in different seasons. Coronary heart disease can be more fatal in low temperatures. The various risk factors are
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Environmental factors like temperature and ultraviolet (UV) radiation.
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Lifestyle factors - obesity, exercise, diet, and smoking.
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Coagulation factors.
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Acute and chronic infections.
Temperature:
There is residual variation in cardiovascular diseases due to differences in Environmental temperature. A lower temperature may exert a direct effect on the heart.
Indirect effects can occur due to changes in blood pressure.
In very low temperatures, conditions like angina can worsen.
In low temperatures, the body surface is cooled and causes peripheral vasoconstriction resulting in increased cardiac output, circulating noradrenaline, and blood pressure.
The cardiovascular changes to temperature in a healthy adult are less, or the body can cope with the situation.
Low temperature or cold is associated with high systolic and diastolic blood pressure. The oxygen consumption of the heart is increased. The increased demand cannot be met in a compromised circulation of the heart, and this leads to myocardial ischemia and later results in angina pectoris or myocardial infarction. Long-term variations and blood pressure can lead to coronary heart disease.
Coronary heart disease mortality is strongly associated with temperature deviation from the average temperature. Extreme variations in hot and cold temperatures can increase coronary heart disease mortality. In cold Climatic temperatures, insulation has a protective effect.
People living in higher altitudes with lower temperature conditions have a reduced incidence of developing coronary heart disease.
Ultraviolet Radiation:
Exposure of the skin surface to sunlight leads to vitamin D synthesis. And lower levels of vitamin D can be linked to coronary heart disease.
This relation should be independent of other factors like smoking, medications for hypertension, body mass, and previous history of angina.
Serum Cholesterol Level:
The level of vitamin D affects the serum cholesterol level, which is a risk factor for heart disease. The level of vitamin D decreases during cold climate conditions and leads to higher levels of cholesterol.
Coagulation Factors:
Hematologic parameters like hemoglobin level, erythrocyte sedimentation rate(ESR), hematocrit, fibrinolytic activity, and platelet levels show changes in a change in environmental temperature. Lower temperatures can increase platelets and red blood cells. The plasma volume is also reduced. Lower temperature and increased incidence of respiratory infections result in winter rise of fibrinogen concentrations. The changes in coagulation factors are linked to seasonal variations in cardiovascular disease and venous thromboembolic disorders.
Acute Respiratory Infections:
Cardiovascular disease and respiratory infections show a peak during the winter season. Reduced temperature can suppress the immune system and leads to a high risk of respiratory infections. Respiratory infections like influenza increase the plasma fibrinogen and inhibition of fibrinolysis. These vascular changes increase the risk of arterial thrombosis and developing coronary heart disease. The changes associated with the respiratory system are primarily seen in elderly people.
Age and Sex:
Age and sex are not important factors in the seasonal variation of heart diseases.
Coronary heart disease mortality increases with age in winter peaks. It is also linked to other factors like less physical activity, spending more time outside, less use of protective clothing, and poor household heating. Previous history of coronary heart disease can aggregate in such conditions.
Time Trend:
In the USA, there is a time trend for the seasonality of diseases. Similarly, the prevalence of various heart diseases has a time trend concerning climatic changes and other risk factors.
What Are the Lifestyle Factors Affecting the Cardiovascular Diseases?
Diet and Obesity:
Body weight also shows variations in seasons. Obesity is common during the winter season due to less physical activity and high intake of fat. Diet does not have much effect over seasons. Intake of vitamin C is also reduced in winter. These can be a factor for changes in cardiovascular activity.
Exercise:
It is important to stay physically active and fit for good functioning of the heart and to stay away from heart problems. An inactive or sedentary lifestyle can be a risk factor for heart disease.
Certain physical activities are done only during certain periods. Generally, physical activity is very less during winter seasons. Simple activities like cycling, walking, and exercise help to improve cardiac function. And the effects of temperature will not be affected seriously. At the same time, high levels of physical activity in low temperatures can increase the mortality rate. It has deleterious effects on heart functioning and can cause death.
Smoking:
In cold climate conditions, smoking also increases. Since smoking is an important risk factor for heart disease, it should be controlled.
Conclusion
Seasonal variations are reported in various regions with extreme climatic conditions. Proper study related to seasonal variations can help reduce the prevalence and mortality of diseases. Underlying heart diseases, age, physical inactivity, less use of protective clothing, and inadequate indoor heating can make the condition severe and lead to death. Understanding the seasonal variations and preparing the body to keep a healthy heart functioning is of prime consideration. The mortality and morbidity rate increases during the winter, than the summer season.
Seek help from a doctor or health care provider to have customized changes to the lifestyle and to follow.
