Why does shoulder bursitis worsen at night?

Why Shoulder Bursitis Worsens at Night

Shoulder bursitis worsens at night primarily due to circadian-driven increases in inflammatory mediators, particularly IL-1 and IL-6, combined with cortisol nadir, increased local tissue pressure from immobility, and heightened pain perception during rest.

Circadian Inflammatory Mechanisms

The nighttime exacerbation of shoulder bursitis follows well-established circadian patterns of inflammation:

• IL-1-mediated inflammation increases at night with less diurnal variation compared to anti-inflammatory cytokines like IL-10, creating a pro-inflammatory environment that amplifies bursal inflammation 1
• IL-6 levels peak during nighttime hours and correlate directly with poor sleep efficiency and increased pain perception in inflammatory conditions 1
• T-cell upregulation occurs nocturnally, with peak activity around 2 AM, contributing to sustained inflammatory responses in affected tissues 1
• Cortisol reaches its nadir during nighttime, removing the natural anti-inflammatory suppression that occurs during daytime hours 1

Biomechanical and Positional Factors

Physical factors during sleep directly worsen bursal inflammation:

• Immobility during sleep increases local tissue pressure and reduces circulation to the subacromial bursa, exacerbating inflammation and pain 2
• Sleeping positions compress the affected shoulder, particularly when lying on the symptomatic side, increasing mechanical stress on already inflamed bursal tissue 2
• Reduced movement eliminates the pain-relieving effects of motion, similar to mechanisms seen in other inflammatory conditions where symptoms worsen with rest 1

Neurophysiologic Pain Amplification

Nighttime pain perception differs fundamentally from daytime:

• Heightened sensitivity to sensory stimulation occurs at night due to nerve fiber dysfunction and increased expression of sensory neuron receptors in inflammatory states 1
• Absence of daytime distractions allows greater conscious awareness of pain signals from the inflamed bursa 1
• Sleep stage transitions trigger brief arousals that make patients more aware of ongoing shoulder pain, particularly during lighter N1 and N2 sleep stages 1

Clinical Implications

Understanding these mechanisms guides management:

• Anti-inflammatory medications should be timed to provide peak effect during nighttime hours when inflammatory mediators surge 1
• Positioning strategies are critical: patients should avoid sleeping on the affected shoulder and use pillows to support proper shoulder alignment 2
• Evening corticosteroid dosing may be more effective than morning administration for controlling nighttime symptoms, though this requires individual assessment 1
• NSAIDs taken before bedtime can help blunt the nocturnal inflammatory surge 3

Common Pitfalls

• Do not dismiss nighttime pain as purely psychological - it reflects genuine circadian inflammatory biology 1
• Avoid attributing all nighttime shoulder pain to bursitis alone - evaluate for concurrent rotator cuff pathology, adhesive capsulitis, or impingement syndrome which share similar nocturnal patterns 4, 2
• Recognize that constant nighttime pain may indicate more severe inflammation requiring aggressive treatment, as three patients with constant pain showed no bursal inflammation but had inflammation in adjacent tissues 5