Which statement best describes fatigue in primary multiple sclerosis?

• A. It is typically alleviated by rest and does not worsen with heat.
• B. It is unrelated to sleep quality.
• C. It is always resolved by sleep for several hours.
• D. It is often worse in the afternoon or evening.

Answer: (D)

Fatigue in primary multiple sclerosis is an intrinsic, often disabling symptom that tends to vary with the time of day and environmental factors. It isn’t simply a consequence of sleep loss, and while good sleep can help, rest alone doesn’t guarantee lasting relief or complete resolution. Heat sensitivity often makes fatigue worse, so warmer environments or sustained activity can push fatigue higher. Because energy reserves and body temperature interact, many people notice a diurnal pattern with more fatigue later in the day, especially in the afternoon or evening as the day wears on. That combination—the common occurrence of fatigue, its amplification with heat, and its tendency to worsen as the day progresses—explains why the statement describing it as often being worse in the afternoon or evening is the best fit. The other options misstate the relationship to sleep, heat, or the persistence of fatigue, which is why they aren’t as accurate.