What causes hypertension in winter?

Causes of High Blood Pressure in Winter

Blood pressure rises in winter primarily due to cold-induced vasoconstriction and increased sympathetic nervous system activity, with temperature being the single most important environmental factor driving seasonal BP elevation. 1

Primary Physiological Mechanisms

Cold exposure triggers multiple cardiovascular responses that directly elevate blood pressure:

• Skin cooling increases vascular resistance and plasma noradrenaline concentration, which are the primary drivers of winter BP elevation 2
• Sympathetic nervous system activation intensifies during cold weather, leading to increased catecholamine release and heightened vascular tone 3, 4
• For every 1°C decrease in outdoor temperature, systolic BP increases by approximately 0.19 mmHg and diastolic BP by 0.12 mmHg in hypertensive patients 5
• The average winter BP elevation is 5/3 mmHg (systolic/diastolic) compared to summer, with this effect being more pronounced in treated hypertensive patients 6, 1, 7

Secondary Contributing Factors

Beyond direct temperature effects, several winter-associated factors compound BP elevation:

• Increased sodium load presented to the kidneys for excretion occurs in winter, contributing to volume expansion and BP rise 3
• Respiratory infections peak during colder months, which can precipitate cardiovascular stress and BP elevation 2
• Vitamin D insufficiency during winter months has been linked to worsening cardiovascular parameters including BP 2
• Reduced physical activity in cold weather contributes to BP elevation, though temperature itself remains the dominant factor 2, 4

High-Risk Populations

Certain patient groups experience more pronounced winter BP increases:

• Elderly patients show greater BP variability with temperature changes and face higher cardiovascular risk during winter months 2, 7
• Patients already on antihypertensive therapy demonstrate larger seasonal BP fluctuations (average 5/3 mmHg change) compared to untreated individuals 1, 7
• Those with higher baseline BP experience more pronounced temperature-related BP changes 5
• Obese patients, females, and those with low socioeconomic status show stronger associations between cold temperature and BP elevation 5

Clinical Implications

The winter BP surge has direct mortality and morbidity consequences:

• Cardiovascular hospitalizations increase substantially during colder periods, with temperature having the greatest inverse correlation with cardiovascular events among all environmental factors 2
• Winter hospitalization is associated with both poorer short-term and long-term prognosis in cardiovascular patients 2
• The Christmas winter period shows the highest rates of excess all-cause and cardiovascular deaths 2

Management Considerations

Proactive strategies can mitigate winter BP elevation:

• Home BP monitoring throughout the year is essential to detect and quantify seasonal variations before clinical complications arise 8, 7
• Early titration of antihypertensive medications before winter should be considered for patients with documented seasonal BP patterns 8, 7
• Appropriate clothing and heating strategies must be optimized to stabilize body core temperature and prevent excessive cold exposure 2
• Reducing exposure to cold temperature is specifically recommended as part of lifestyle modifications for hypertension management 1

Common Clinical Pitfalls

Avoid attributing winter BP elevation solely to medication non-adherence - the physiological response to cold is a real and significant contributor that requires recognition and management 7

Do not ignore symptoms of overtreatment when weather warms - the same patient may require medication adjustment as seasonal temperatures rise and BP naturally declines 1, 7

Never assume indoor heating eliminates the problem - even with central heating, exposure during transitions and inadequate home heating in vulnerable populations remains problematic 2