The lights are off. The room is quiet. The body is tired. Yet the brain keeps talking. For many older adults, especially those in their 60s and beyond, this pattern becomes a nightly battle. Sleep does not just disappear. It slowly fragments. The mind begins to replay conversations, plan tomorrow’s tasks, or drift into restless mental chatter.A study titled “Cognitive-affective disengagement: 24h rhythm in insomniacs versus healthy good sleepers” explored why this happens. It compared people with sleep maintenance insomnia to healthy sleepers over a controlled 24-hour period. What it found offers an important clue: some brains fail to switch off at night because they struggle to disengage emotionally and cognitively.Insomnia is not just about poor sleep. It is about a brain that stays alert when it should power down.
The brain has a 24-hour rhythm
The human brain runs on a circadian rhythm. It rises in alertness during the day and dips at night. Mood, thinking speed, and emotional tone follow this cycle.Research from the National Institute of General Medical Sciences (NIGMS), NIH explains how circadian rhythms regulate sleep and brain activity.In healthy sleepers, mental activity peaks in the afternoon and drops to its lowest point in the early morning hours. This drop allows the brain to detach from goal-oriented thinking. Thoughts become less structured. The mind drifts. But in people with insomnia, the rhythm flattens.The recent study found that while both groups showed circadian patterns, insomniacs had less variation across 24 hours. Their brains did not dip as deeply into night-time disengagement. It is as if the mental volume knob refuses to turn down fully.
What is cognitive-affective disengagement ?
Cognitive-affective disengagement means the brain reduces thinking and emotional processing before sleep.
In healthy sleep:
- Thoughts become less structured.
- Mental images feel more dream-like.
- Emotional intensity softens.
- Voluntary control over thinking reduces.
In insomnia:
- Thoughts remain sequential and logical.
- The mind stays “real-world” focused.
- There is continued goal-oriented processing.
- Prefrontal regions may remain more active.
This supports the hyperarousal model of insomnia. According to the National Heart, Lung, and Blood Institute (NHLBI), insomnia often involves an overactive mind at night. Instead of drifting, the brain keeps organising.
Healthy sleepers shift toward less controlled mental activity. Insomniacs maintain structured thought patterns.
Sequential thinking: The nighttime trap
One striking finding in the study was the presence of elevated sequential thinking at night among insomniacs.Sequential thinking is structured. It moves step by step. It plans. It analyses. That type of thinking is useful during the day. It becomes a problem at midnight.Healthy sleepers shift toward less controlled mental activity. Insomniacs maintain structured thought patterns. The study suggests this may contribute to staying awake.This trait-like difference may act as a fuel source for wakefulness. When the mind keeps solving, sleep waits outside the door.
What happens to the brain without proper shutdown?
Chronic insomnia affects more than mood. It changes how the brain functions.The Centers for Disease Control and Prevention (CDC) reports that insufficient sleep is linked to poorer concentration, slower reaction times, and emotional instability.
Long-term insomnia is associated with:
- Impaired memory consolidation
- Increased stress hormone levels
- Higher risk of depression and anxiety
- Reduced emotional regulation
Functional brain imaging studies have shown that the prefrontal cortex, responsible for planning and reasoning, may remain more active in insomniacs at night.Sleep is not passive. It is a biological reset. When that reset weakens, the brain pays the price.
Why does the brain stay alert?
Several factors may drive this night-time alertness:Flattened circadian amplitudeThe study found insomniacs had smaller 24-hour variation in mental states. The night dip was weaker.Emotional carryoverStress hormones remain elevated. The body fails to signal safety.Conditioned wakefulnessRepeated nights of poor sleep train the brain to associate bed with alertness.Age-related rhythm shiftsCircadian rhythms weaken with age, which may explain why the study group, averaging mid-60s, showed these patterns.
Some people may have stronger circadian rhythm disturbances. Others may have cognitive traits that keep thoughts sequential.
Can the brain be trained to switch off?
Yes, and this is where the study offers hope.It suggests that strengthening circadian rhythm and modifying sequential thinking could help.Evidence-based strategies include:
- Strengthen the circadian rhythm
- Morning sunlight exposure within one hour of waking.
- Fixed sleep and wake times, even on weekends.
- Avoiding bright light at night.
The National Institute on Aging (NIA) notes that consistent schedules improve sleep in older adults.
Reduce sequential thinking at night
Cognitive Behavioral Therapy for Insomnia (CBT-I), the gold standard treatment.
- Scheduled “worry time” earlier in the evening.
- Journaling before bed to externalize planning thoughts.
- CBT-I has been recommended by major health bodies because it directly targets hyperarousal patterns.
Train emotional down-regulation
- Slow breathing exercises.
- Body-based relaxation techniques.
- Guided imagery that shifts thought modality from structured to visual.
The goal is not to force sleep. It is to help the brain let go.The study highlights that insomnia is not identical for everyone. Some people may have stronger circadian rhythm disturbances. Others may have cognitive traits that keep thoughts sequential.
