Does sickle cell trait (SCT) cause symptoms in cold weather and what are the symptoms?

Sickle Cell Trait and Cold Weather Symptoms

Sickle cell trait (SCT) does not typically cause symptoms in cold weather under normal daily conditions, but individuals with SCT do exhibit increased sensitivity to cold temperatures and may experience serious complications under extreme physiological stress combined with cold exposure.

Key Distinction: Trait vs. Disease

The provided guidelines focus primarily on sickle cell disease (SCD), not sickle cell trait 1. Individuals with SCT (HbAS) are generally asymptomatic carriers and do not experience the chronic complications seen in sickle cell disease 1. The heterozygous carrier state only becomes clinically important at extremes of physiology 1.

Cold Sensitivity in Sickle Cell Trait

Documented Thermal Hypersensitivity

• Patients with sickle cell disease (not trait) demonstrate significantly increased sensitivity to cold temperatures, detecting cold sensations sooner (median cold detection threshold 29.5°C vs. 28.6°C) and experiencing cold pain at higher temperatures (21.1°C vs. 14.8°C) compared to controls 2.
• This thermal hypersensitivity suggests peripheral or central sensitization may exist in sickle cell conditions 2.
• The evidence for thermal sensitivity specifically in SCT individuals (as opposed to SCD) is limited in the provided literature.

Potential Complications in Extreme Conditions

High-Risk Scenarios for SCT

While SCT carriers are typically asymptomatic, complications can occur under specific extreme conditions:

Triggering Factors:

• Prolonged hypoxia (high altitude, airplane travel) 3
• Severe dehydration 3, 4
• Intense physical exertion, particularly in hot climates 1, 5
• Extreme physical stress 6

Documented Complications (Not Specifically Cold-Related):

• Splenic infarction (most common, typically after high altitude exposure or air travel) 3, 4
• Renal papillary necrosis 3, 4
• Gross hematuria 4
• Exercise-related collapse (typically in heat, not cold) 1

Cold Weather Considerations

The evidence does not support that routine cold weather exposure causes symptoms in SCT individuals 1. The complications documented in SCT occur primarily with:

• Hypoxia at altitude 3
• Extreme exercise in heat (≥80°F temperatures) 1
• Dehydration 3

Mechanical Properties

• RBCs from SCT individuals are inherently stiffer and more viscous than normal RBCs, but oxygen level variations do not alter their mechanical properties or morphology 6.
• This suggests that cold-induced changes are less likely to trigger sickling in trait carriers compared to disease patients 6.

Clinical Implications

When to Suspect SCT-Related Complications

Consider hemoglobin studies in patients of compatible ethnic origin presenting with:

• Splenic infarction after altitude exposure 3
• Renal papillary necrosis 3
• Markedly elevated C-reactive protein in these contexts 3

Operational Outcomes

• SCT-positive U.S. Air Force airmen had similar career and operational outcomes to SCT-negative peers, with no restrictions placed on occupation choice or deployment to high-elevation locations 5.
• SCT-positive airmen spent slightly less cumulative time at high-elevation assignments but had similar deployment rates 5.

Common Pitfalls

• Do not confuse sickle cell trait with sickle cell disease—the clinical presentations and risks are vastly different 1.
• Cold weather alone, without additional stressors (hypoxia, extreme exertion, dehydration), does not typically trigger complications in SCT 1, 3.
• The thermal hypersensitivity documented in research applies to sickle cell disease patients, not necessarily trait carriers 2.