The latest iPhone software update, iOS9.3, wasn’t particularly notable. The dashboard on the Health app changed slightly, and the 'notes' section is now fingerprint-protected (which, frankly, has left my To Do lists with an over-heightened sense of their own importance). But it also introduced a feature which, while small, could revolutionise the way our phones affect our health: a blue light reduction app called. Night Shift uses geolocation and sunset time data to reduce the blue light in its display after sunset. The result isn’t a lack of blue on the screen, but a sort of filtered, amber look. This colour change, allegedly, could improve our sleeping patterns. I’d guess that most under-30s have heard of blue-blocking apps, but probably from friends who fall at the tinfoil hat end of the 'interested in science' spectrum. But Adrian Williams, a professor of sleep medicine at Kings’ College and the London Sleep Centre, tells me that sleep experts have been prescribing “blue-blocking” apps for years: “I recommend them all the time – they’re strongly backed up by evidence.” As Williams says, multiple studies have shown that the blue wavelengths on the white light spectrum can disrupt our sleep patterns, because we only expect to see light in this spectrum during the day.

RELATED: Artificial Light Is Wrecking Your Sleep, and It’s Time to Do Something About It There is a growing body of research suggesting that exposure to artificial light late into the evening, especially blue light like the crisp blue-white glow of our beloved gadgets, is a serious issue that effects our sleep cycles and general health. You can, however, minimize the effect of late-night. Stalin said the way to take over a nation.

It’s what makes both daylight and our phone screens look particularly bright and alert, while everything at night appears more dulled. As a result, scientists believe, exposure at night can confuse our “circadian rhythms” so our bodies lose track of when to sleep and wake up.

These rhythms, the theory goes, take their cues from blue light, which triggers melatonin production in our bodies. Blue-blocking apps have been around for a while, but until now they were only available on Android devices.

Williams tells me that the inclusion of a blue-blocking app within Apple’s operating system, as opposed to as an add-on, is a significant step forward. While it’s not clear whether blue light affects us all in the same way, it’s fair to say that if you’re having trouble sleeping, blue light should be a first port of call. “We assume that if people are complaining about their sleep then they should avoid late blue light exposure,” Williams says. But is that enough? Advice about keeping devices out of the bedroom stems partly from the problems with blue light, but that isn’t the whole story. Williams tells me he’d advise to patients avoid light and distractions altogether in the bedroom, which, you guessed it, covers even a blue-blocked iPhone or tablet: “The bedroom is for sleep and sex. It’s not clear how much blue light the iPhone app actually blocks, nor how much we should avoid to keep our circadian rhythms ticking over.

Williams hasn’t tried it himself yet, though he has it downloaded, as he goes to bed at 9pm every day. He does say, however, that any reduction in the 'intensity or duration' of blue light on our eyeballs after nightfall can be beneficial.

Until we know more, though, these apps may not help us much – especially if we lose any qualms about staring at our phones late into the night. Note: Annoyingly, this feature is not available on the iPhone 4, 4S, 5, or 5C, or any of the older iPads.