What is Middle Insomnia (Sleep-Maintenance Insomnia)?
Middle insomnia, also called sleep-maintenance insomnia, is difficulty maintaining sleep throughout the night, characterized by multiple nocturnal awakenings or prolonged periods of wakefulness after initially falling asleep. 1
Defining Characteristics
Middle insomnia is objectively defined as wake time after sleep onset (WASO) exceeding 30 minutes. 1 This distinguishes it from brief, normal arousals that occur during sleep transitions. The condition also manifests as:
- Sleep efficiency below 85% (the ratio of total sleep time to time spent in bed), indicating fragmented and disrupted sleep architecture 1
- Multiple awakenings during the night with difficulty returning to sleep 2
- Chronic nonrestorative or poor quality sleep despite adequate opportunity to sleep 2
Clinical Assessment Questions
When evaluating for middle insomnia, clinicians should ask two specific questions:
- "How many times do you wake up at night?" to quantify awakening frequency 1
- "When you wake up, do you have trouble falling back asleep?" to differentiate brief arousals from sustained wakefulness 1
Document total wake time after sleep onset using sleep diaries alongside any objective measures. 1
Age-Related Patterns
Middle insomnia is the predominant sleep complaint in older adult populations, whereas younger adults more commonly report difficulty initiating sleep (sleep-onset insomnia). 1 This higher prevalence in geriatric patients reflects age-related changes in sleep architecture. 1
Diagnostic Criteria for Chronic Insomnia Disorder
For middle insomnia to meet criteria for chronic insomnia disorder:
- Symptoms must occur ≥3 nights per week and persist for ≥3 months 1
- The insomnia occurs despite adequate opportunity and circumstances for sleep, ruling out environmental or situational causes 2, 1
- The condition must cause clinically significant distress or daytime impairment such as fatigue, cognitive dysfunction, mood disturbance, or reduced quality of life 2, 1
Critical Clinical Pitfalls
Middle insomnia should not be dismissed as a normal part of aging—when it leads to distress or functional impairment, it warrants active treatment. 1 This is a common error that results in undertreatment of a treatable condition.
The presence of middle insomnia often signals underlying comorbidities such as depression, anxiety, chronic pain, obstructive sleep apnea, or restless legs syndrome, which should be evaluated and addressed. 1 The etiology of insomnia is typically multifactorial, and perpetuating factors develop over time that require specific treatment even when comorbid conditions are managed. 2
Temporal Stability Considerations
Middle insomnia subtypes show limited temporal stability—only about half of patients with a specific insomnia pattern at initial evaluation maintain that same pattern 4 months later. 3 This instability underscores the importance of ongoing reassessment rather than assuming a fixed diagnostic category.