What the Question Actually Asks
A WiFi router does not go quiet when the household sleeps. It broadcasts beacon frames at regular intervals so devices can find it, and connected devices continue exchanging traffic in the background. The overnight hours are therefore a block of continuous transmission, in a home where people are stationary for eight hours at fixed distances from the source.
Of the 102 peer-reviewed studies indexed here on radiofrequency exposure, 81 — 79.4% — reported measurable biological effects. None of them tested a router being switched off.
What the Sleep Research Supports
The most relevant human work exposed volunteers to pulsed 900 MHz fields and measured sleep directly. Huber and colleagues (2000) exposed young men for 30 minutes before sleep at a spatial peak absorption rate of 1 W/kg and found increased non-REM spectral power during subsequent sleep, concluding that the brain changes outlast the exposure period. Borbély and colleagues (1999) exposed subjects through an entire night on a 15-minutes-on, 15-minutes-off schedule and found altered sleep EEG along with reduced waking after sleep onset, from 18 minutes to 12 — an effect they described as possibly sleep-promoting.
Huber and colleagues (2002) established which property of the signal matters: pulse-modulated exposure changed regional cerebral blood flow and sleep EEG, while exposure without pulse modulation did not. WiFi transmits in bursts, which places it in the category that produced effects rather than the category that did not.
Mann and Röschke (1996) found shortened sleep onset with suppressed REM sleep, both reduced in duration and percentage.
The Honest Gap
Every one of those studies used a source beside the head at intensities comparable to a phone in use. A router several meters away delivers a small fraction of that. Nobody has run the experiment that matters here — sleepers exposed to household WiFi at household distances, with and without the router on, measured on polysomnography.
So the case for switching it off is not that research proved a benefit. It is that pulsed radiofrequency demonstrably affects sleep brain activity at higher doses, that the effects persist beyond the exposure, that nobody has established a threshold below which they stop, and that eliminating eight hours of exposure costs nothing when the network is not in use.
The Other Pathway
Thomée and colleagues (2011) followed 4,156 young adults and found high mobile phone use predicted sleep disturbance and mental health symptoms a year later, including in people symptom-free at baseline. That association involves screen light, alerts and late-night availability as much as radiofrequency exposure. Turning off the WiFi addresses that pathway too, and for many households it is the larger effect.
How to Do It
A plug-in timer switching the router off at bedtime and on in the morning automates the whole thing for the price of a coffee. Many routers have a built-in schedule in their admin settings. If devices need the network overnight — backups, security cameras, a work laptop syncing — a wired connection for those devices lets the wireless radio go off while the network stays up.
What Not to Expect
No study here promises better sleep from this change. Anyone who tries it and sleeps better may be responding to the absence of phone alerts and screens as much as anything else. The defensible claim is narrower: it removes a continuous exposure during the hours the body spends on repair, at no cost and no inconvenience once automated.
