Why does aortic dissection occur more frequently during winter?

Why Aortic Dissection Occurs More Frequently in Winter

Aortic dissection exhibits a significant chronobiological pattern with peak occurrence during winter months due to the relative changes in temperature and atmospheric pressure, rather than absolute cold temperatures alone. 1

Chronobiological Patterns of Aortic Dissection

• Aortic dissection demonstrates a clear seasonal variation with highest incidence in winter (33.6%) and lowest incidence in summer (19.9%) 2, 3
• The peak month for aortic dissection occurrence is January 4
• Within a week, aortic dissections occur most frequently on Wednesdays (15.5%) and Mondays (15.2%), with the lowest frequency on Sundays (12.8%) 3

Physiological Mechanisms Behind Winter Predominance

Temperature and Atmospheric Pressure Effects

• Month-specific incidence of aortic dissection is significantly inversely correlated with mean temperature (higher incidence with lower temperatures) 3
• There is a direct correlation between atmospheric pressure and aortic dissection occurrence (higher pressure correlates with more cases) 3
• The winter peak in aortic dissection is evident in both cold and temperate climate settings, suggesting that relative temperature changes rather than absolute cold temperatures are the critical factor 2

Hypertension and Winter Blood Pressure Changes

• Hypertension is the main risk factor for aneurysm formation and subsequent aortic dissection, found in 85% of patients with ruptured aneurysms 1
• Blood pressure tends to be higher during winter months due to peripheral vasoconstriction in response to cold temperatures 1
• Increased blood pressure directly increases wall stress according to the law of La Place (σ=pr/2h), where wall stress (σ) is directly proportional to pressure (p) and radius (r) 1

Vascular Wall Vulnerability in Winter

• Cold temperatures can increase arterial stiffness, making the aortic wall more vulnerable to shear stress 1
• Reduced nutritional supply to the aortic media due to vasoconstriction of vasa vasorum in cold weather may contribute to medial thinning and necrosis 1
• Atherosclerotic changes in the aortic wall, which are common in patients with aortic dissection, may be exacerbated by winter-related hemodynamic changes 1

Clinical Implications

• Healthcare providers should maintain higher vigilance for aortic dissection during winter months, especially in patients with risk factors 4
• Patients with known aortic aneurysms or predisposing conditions (Marfan syndrome, hypertension) may benefit from more aggressive blood pressure control during winter 1
• The relative risk of aortic dissection in winter is 1.519 compared to other seasons, highlighting the importance of seasonal awareness 3

Additional Factors Influencing Aortic Dissection Timing

• The proportion of Stanford Type A dissections (involving the ascending aorta) is significantly higher during full moon phases (73.7% vs 66.9% for Type B) 3
• Inflammatory processes within the aortic wall may be influenced by seasonal variations in immune function 1
• Biomarkers such as C-reactive protein (CRP) and matrix metalloproteinases (MMPs), which play roles in aortic wall degradation, may show seasonal variations 5

Understanding these chronobiological patterns can help improve disease prevention strategies and optimize healthcare resource allocation, particularly in emergency departments during winter months when aortic dissection cases are more likely to present 3.