# Night-shift fatigue: what a circadian assessment looks at

A circadian evaluation considers sleep timing, symptoms, environment and other sleep disorders. Hormone measurements are only one possible part.

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Publisher: Velri (https://velri.co/about)
Published: 2026-06-14
Updated: 2026-09-30
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Persistent fatigue on night shifts can involve more than the total number of hours spent in bed. A circadian assessment asks whether the timing of sleep and wakefulness fits the body's rhythm, while also considering sleep quality and other medical causes. [1][2]

## What pattern is the clinician looking for?

NHLBI describes a review of symptoms, sleep patterns, environment, health history and physical findings. A sleep diary can record when sleep actually happens and how well it works. [1]

For a rotating schedule, the comparison between workdays and days off is especially useful. Trouble sleeping during the available window, sleepiness while working and repeated schedule changes are different parts of the pattern. [1][3]

## Which measurements may help?

Actigraphy uses a small motion sensor over several days to examine rest and activity patterns. A sleep study may be used when another sleep disorder is suspected. These tests answer different questions from routine bloodwork. [1][3]

In some assessments, repeated measurements of melatonin, cortisol or body temperature can help characterize the body's rhythm. NHLBI describes looking at how these rise and fall over time, rather than treating one value as a complete circadian profile. [1]

## What else needs consideration?

An examination can look for conditions that interfere with sleep, including pain or features that suggest sleep apnea. A fatigue evaluation may also consider medicines, anemia, thyroid disease and mood-related conditions. [1][2]

## What makes a record useful?

Note actual sleep and wake times, naps, awakenings, caffeine, and periods of sleepiness. Include days off and any change in the work rotation. These are among the details NHLBI recommends for a sleep evaluation. [3]

## Sources
[1] Circadian Rhythm Disorders - Diagnosis | NHLBI, NIH (2022). https://www.nhlbi.nih.gov/health/circadian-rhythm-disorders/diagnosis
[2] Fatigue: MedlinePlus Medical Encyclopedia (2025). https://medlineplus.gov/ency/article/003088.htm
[3] Insomnia - Diagnosis | NHLBI, NIH (2022). https://www.nhlbi.nih.gov/health/insomnia/diagnosis

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