Nighttime Uhthoff’s in MS

Most people with MS know that hot weather or exercise can temporarily worsen symptoms. But many are surprised to find that the same thing can happen at night — in bed, under blankets, or even after a mild fever. This is Uhthoff’s phenomenon, and it affects up to 80% of people with MS.

What Is Uhthoff’s Phenomenon?

Uhthoff’s phenomenon is a temporary worsening of MS symptoms when body temperature rises. Even a small increase of 0.5°C (less than 1°F) can slow nerve conduction in demyelinated pathways. At night, body heat can rise from:

Warm blankets, mattresses, or room temperature
Hormonal changes (night sweats, menopause, etc.)
Fever or mild illness
Hidden overheating from late-day exercise or heavy meals

Unlike relapses, these changes are reversible — once body temperature cools, symptoms ease.

Why It Feels Worse at Night

At night, the body naturally goes through cycles that can worsen Uhthoff’s effect:

Core temperature rises slightly during deep sleep, especially in the first half of the night.
Blankets and bedding trap heat, creating a microclimate around the body.
Poor cooling (if the room is warm, stuffy, or without airflow) makes it harder to regulate temperature.
Fever or infections can amplify the problem, leading to symptom spikes even if you’re lying still.

Patients often report:

Blurred or dimmed vision
Sudden fatigue or weakness
Tingling, numbness, or burning sensations
Worsened balance or coordination
Spasms or stiffness feeling more severe in bed

Why It’s Not a Relapse

This distinction is important. Uhthoff’s phenomenon does not mean new damage is happening in the nervous system. It’s the same nerve fibers temporarily struggling to conduct signals when overheated. Once cooled, they work again.

That’s why symptoms can disappear by morning, after cooling down overnight or adjusting sleep conditions.

What Can Help

Small adjustments often make a big difference:

❄️ Keep the bedroom cool: Aim for 60–67°F (16–20°C).

🌀 Use airflow: A fan or open window helps reduce trapped heat.

🛏️ Cooling bedding: Breathable fabrics, moisture-wicking sheets, or cooling gel pillows prevent heat build-up.

🚿 Cool shower before bed: Lowers core temperature and delays overheating.

💧 Stay hydrated: Water helps regulate temperature naturally.

🧊 Cooling aids: Neck wraps, ice packs, or even chilled socks can reduce heat during flares.

📋 Track patterns: If symptoms worsen predictably at night, noting them can help identify triggers (e.g., meals, exercise, or room setup).

Key Takeaway

Uhthoff’s phenomenon can make MS symptoms flare up suddenly at night, even when you’re just lying in bed. The good news is that it’s temporary and reversible — not a relapse. By understanding why it happens and making small cooling adjustments, you can protect your sleep and ease nighttime symptoms.

💬 Have you noticed your MS symptoms worsen at night? Share your experiences — your tips may help others cool down and rest easier.

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