When Your Body Is in Bed but Your Brain Won’t Clock Out

Many of us have had that frustrating moment: the room is quiet, the lights are off, and yet sleep won’t come. Your heart beats a little faster, your jaw stays tense, and your mind keeps running through tomorrow’s to-do list. This mix of body tension and mental buzz is called pre-sleep arousal, and it’s one of the key reasons people struggle to fall asleep. The widely used Pre‑Sleep Arousal Scale (PSAS) helps clinicians and researchers measure this problem. But to use it well across cultures, the tool must be accurate and reliable in each language.

The research paper Psychometric properties of a Korean version of the pre-sleep arousal scale takes on that challenge. It evaluates how well a Korean translation of the PSAS works: whether it measures what it’s supposed to measure, whether its items hang together logically, and whether the scores are consistent. In short, it tests the psychometric properties—the statistical DNA—of the Korean PSAS (K‑PSAS).

Why this matters is simple: sleep difficulties are common and costly for health, work, and relationships. If professionals in Korea can confidently assess the mental and physical “revving” that happens before bed, they can target treatment more precisely. This study shows that a refined 15‑item version of the K‑PSAS is both valid (it measures pre-sleep arousal as intended) and reliable (it does so consistently). It also offers an important insight: one item didn’t fit the pattern and was removed, leading to a cleaner, stronger tool.

What the Numbers Say About Racing Minds and Restless Bodies

The research team analyzed data from 286 Korean adults aged 19–70 who used electronic cigarettes or heated tobacco products. After translating the original 16‑item PSAS into Korean and having experts review it, they examined how the items grouped together statistically. The experts’ agreement on relevance was unanimous: both the item-level and overall content validity indices were 1.0, indicating every item looked appropriate on its face.

But when the team tested how the items behaved in real data—a process called factor analysis—one item didn’t play well with the rest. The item about “being mentally alert and active at bedtime” showed weak links to the overall scale and even had a slightly negative connection to the total score. Removing this item created a 15‑item version, the K‑PSAS‑15, that showed a clear two‑factor structure: somatic arousal (body symptoms like a racing heart) explaining 42.36% of the score differences, and cognitive arousal (thought-driven alertness like rumination) explaining another 10.19%.

The two factors weren’t separate worlds; they were meaningfully related (correlation ρ = 0.61), suggesting that in real life, tense bodies and busy minds often go together at bedtime. The K‑PSAS‑15 also lined up well with other trusted measures. People who scored high on it also tended to report worse insomnia, poorer sleep quality, and higher anxiety or depression (correlations ranged from 0.49 to 0.71 with the Insomnia Severity Index, Pittsburgh Sleep Quality Index, and Hospital Anxiety and Depression Scale). Finally, the scale proved internally consistent—its items worked together—showing strong Cronbach’s alpha values: 0.91 for the total scale, 0.87 for somatic items, and 0.90 for cognitive items. Split‑half reliability was also high, meaning two halves of the test told the same story.

Why Measuring Nighttime Tension Matters—and What This Scale Captures

Insomnia is rarely a mystery once you tune into pre-sleep arousal. Decades of sleep research show that both physiological activation (e.g., tight muscles, rapid heartbeat) and cognitive activation (e.g., worry, problem-solving in bed) delay sleep onset and can fragment sleep across the night. The K‑PSAS‑15 cleanly captures these two strands. In this way, it mirrors the original PSAS and aligns with cognitive-behavioral theories of insomnia, which argue that hyperarousal is the core driver of sleep problems.

Consider two real-world snapshots. A graduate student lies in bed replaying a tense email exchange with a supervisor, mentally composing replies and feeling her heart pick up. On another night, a shift worker tries to sleep after a late dinner and an online gaming session; his shoulders stay tight, and he describes feeling “wired” despite fatigue. The K‑PSAS‑15 would likely flag both as elevated on pre-sleep arousal, but for somewhat different reasons—thinking too much vs. a revved-up body. This distinction matters because treatment works best when matched to the problem: techniques like cognitive restructuring for runaway thoughts, and relaxation training for bodily tension.

The decision to drop the “mentally alert and active at bedtime” item is revealing. It might reflect cultural nuance in how alertness at night is described or valued; being “mentally active” could be interpreted as productivity rather than restlessness. Alternatively, the item may simply overlap awkwardly with others, adding noise rather than precision. Either way, its removal improved the structure and consistency of the scale, a common and healthy step in scale refinement.

The study’s sample—adults who use electronic or heated tobacco—adds another layer. Tobacco use can disrupt sleep via nicotine’s stimulating effects, making pre-sleep arousal more likely. That context may have helped highlight the scale’s sensitivity. Still, it also means we should be careful about generalizing to all adults in Korea. The strong reliability and validity findings are encouraging, but continued testing in broader groups will strengthen confidence in the tool’s reach.

From Clinic to Bedroom: Putting the K‑PSAS to Work

For clinicians, the K‑PSAS‑15 offers a quick, precise way to target treatment. In cognitive behavioral therapy for insomnia (CBT‑I), a high somatic arousal score points to adding progressive muscle relaxation, paced breathing, or biofeedback; a high cognitive arousal score suggests emphasizing thought-challenging, scheduled worry time, or mindfulness techniques to reduce mental overdrive. Tracking scores across sessions can show whether a patient’s “revving” is actually calming down, even before total sleep time changes.

In occupational health and business settings, the K‑PSAS‑15 can flag employees at risk for sleep-related productivity dips—think customer service agents who ruminate after tough calls or night-shift staff who feel bodily “wired” after work. Targeted sleep workshops can pair psychoeducation with specific arousal-reduction skills, rather than generic sleep hygiene tips. In workplaces with high nicotine use, the tool can inform integrated programs that address both tobacco reduction and sleep support.

For public health researchers, the scale’s strong links to insomnia, global sleep quality, and mood (anxiety and depression) make it a useful screening instrument in large surveys. Because scores correlate moderately to strongly with these outcomes, interventions that lower pre-sleep arousal may have ripple effects on mental health. In personal life, a simple takeaway is to self‑monitor: notice whether your sleep struggle feels more “in the body” or “in the head.” Align your evening routine accordingly—gentle stretching and heat for tense muscles; a ten‑minute braindump, dim light, and screen cutoffs for racing thoughts.

Finally, for digital health developers, the K‑PSAS‑15 can serve as a clear, validated endpoint. Apps that prompt users with these items weekly could personalize sleep coaching, sending body-focused relaxation tasks to some users and cognitive calming tasks to others, and adjusting content based on subscale changes over time.

A Leaner Scale, A Clearer Signal

The headline here is practical: a 15‑item Korean version of the pre‑sleep arousal scale delivers a cleaner, stronger measure of the nightly “revving” that blocks sleep. The K‑PSAS‑15 shows excellent reliability, a solid two‑factor structure, and meaningful links to insomnia, poor sleep quality, and mood symptoms. It turns a vague complaint—“I can’t turn it off at night”—into a profile that guides action.

For anyone wrestling with sleeplessness, that’s hopeful news. If we can measure pre-sleep arousal clearly, we can treat it more effectively. The next step is simple but powerful: use this tool widely, test it in diverse groups, and keep refining interventions that quiet the body, settle the mind, and make room for restorative sleep. If your nights feel too loud, which dial—body or mind—will you turn down first?

Data in this article is provided by PLOS.

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