AGT and vitamin D deficiency: A study of the underlying mechanisms and factors associated with seasonality of cardiovascular disease mortality reported that cold temperatures during the winter months were associated with increased sympathetic nervous system activation and catecholamine secretion as well as, vitamin D deficiency, high serum cholesterol, lack of physical activity, increase risk of coagulation, blood pressure related hormones such as arginine vasopressin, norepinephrine, and angiotensin II, respiratory infection, age, and sex [24].