Many of us rely on our smartphones to help keep time, manage our lives, connect with others, stay entertained, retain beautiful memories and more.
But we should not have to risk our lives using the device. Last month, a video of a woman in Singapore who was hit by a taxi in Lavender Street while jaywalking and talking on her phone went viral.
Smartphone zombies like her roam the streets and could potentially walk into the path of a car at any minute. Their prevalence has even prompted some to call for legislation to ban pedestrians crossing the road from using mobile phones.
Here is a look at the potential dangers of excessive smartphone use.
NECK, SHOULDERS AND HANDS
Dr Marcus Ling, an associate consultant at the department of orthopaedic surgery at Singapore General Hospital, said many younger patients are seeking medical attention for neck and back aches.
While he cannot be certain if it is due to increased smartphone use, he added that studies have shown that excessive smartphone use is associated with neck and shoulder discomfort.
"This is likely because of the more pronounced head-down tilt posture and increased activity of the neck muscles associated with smartphone use."
Symptoms that patients commonly complain of after excessive smartphone use range from pain of the neck and fingers to fatigue, as shown in a study conducted in southern India in 2016, Dr Ling noted.
Repetitive movements associated with smartphone use, such as swiping, scrolling and tapping, may impact the muscular and nervous tissue of the hand and lead to conditions such as carpal tunnel syndrome and repetitive strain injury.
EYESDr Claudine Pang, an ophthalmologist at Asia Retina Eye Surgery Centre, said she has seen a rising number of patients with digital eye strain symptoms such as eye fatigue, discomfort, teariness, blurred vision, headaches and brow aches.
"Our eyes cannot tolerate staring directly into a light source for too long, so the glare from the back light of digital screens can cause serious eye strain," she added.
"This, in addition to prolonged accommodation (or the focusing) of our eyes, brings about squinting and frowning that translates to further headaches and brow aches."
Dr Pang said using the smartphone when it is held too close to the eyes could also lead to a worsening of short-sightedness or myopia. Children are particularly vulnerable because their eyes are growing and have not fully matured, she added.
"Although adult eyes are supposed to have reached full maturity and stability, there are still some adults who will suffer from worsening myopia if they are exposed to continuous near-work for prolonged and excessive amounts of time," she said.
"The recommended comfortable distance for near work is 50 to 65cm, which is approximately an arm's length from our eyes."
Then, there is the general worry that prolonged exposure to the blue light emitted from smartphones and digital devices might harm the eyes, though not all blue light is harmful.
"Although the amount of blue light emitted by digital screens may be small compared with sunlight, the fact that people are exposing their retinas to prolonged levels of direct blue light may be detrimental to health in ways that are not yet known," said Dr Pang.
Laboratory studies have shown that too much blue light exposure damages retina photo receptors and could lead to macular degeneration.
"However, as these studies were not conducted on human eyes, it is not conclusive as to whether blue light has direct harmful effects on human eyes," said Dr Pang.
Based on the theoretical risk that it could damage our eyes in the long run, it would be useful to get blue-light filters for digital screens or to use built-in blue-light filters in our digital devices, said Dr Pang.
"Spectacle lenses that are able to filter out blue light (although not 100 per cent of it) are also useful as they cut down excessive blue-light exposure to our eyes."
SLEEPStudies have shown that excessive smartphone use could impact sleep not just for adults, but also for toddlers.
Last month, a study published in the European Journal of Paediatrics identified smartphone use as a factor associated with toddlers taking a longer time to fall asleep and sleeping fewer hours, said Dr Ling.
Also, excessive use of smartphones during the night may play a significant role in sleep problems and depressive symptoms among teenagers, according to an article in the International Journal of Adolescent Medicine and Health last year.
THINKINGSmartphones have changed the way we think and behave, said Singapore Management University psychology lecturer Andree Hartanto.
Knowing that we now have instantly accessible knowledge in our pocket at any time, people are more likely to rely on their smartphones for information and to offload their thinking to the device, he added.
"In other words, smartphones allow some people to be slightly lazier in thinking than they would otherwise be."
People may become slightly less creative and analytical, but this is not harmful.
"In fact, we become more efficient in our daily life because of smartphones. I think it is more about the trade-off," he said.
Interestingly, the "smartphone effect" can also spill over to our social relationships, Dr Hartanto added.
He pointed out an experiment in Britain which showed that partners who got to know each other in the presence of a smartphone felt less close to each other.
They also reported a lower quality of relationship than partners who shared a conversation without a smartphone present.
Our addiction to smartphones is real - there is even a term, "nomophobia", which is used to describe the irrational fear of not being able to use your mobile phone, or of misplacing it.
However, smartphone addiction is not recognised as a clinical disorder at the moment, said Mr Suresh Anantha, principal counsellor at the National Addictions Management Service (Nams) at the Institute of Mental Health.
"No one has sought help for smartphone addiction at Nams thus far," he added.
Right now, smartphone addiction is more of a cultural and social phenomenon than a clinical disorder.
"We are still developing norms on how much is too much and such opinions may vary, he said.
"We also haven't developed etiquette and behavioural guidelines, except for when they involve using the phone while driving as well as limiting screen time for young children."
Indeed, how smartphone use impacts us is complex. Dr Hartanto said we do not yet know for sure whether we should let young children use smartphones, whether smartphones decrease our attention span, what is considered excessive use and so on.
Most of the current research on the cognitive and socio-emotional consequences of smartphone use is still preliminary and inconsistent. A lot of factors, including frequency and age, are at play.
Dr Hartanto recently completed a longitudinal study on more than 3,000 elderly people in the United States which showed that frequent computer use can act as a protective factor against cognitive decline as we age.
"We found that higher technology engagement, over a period of approximately nine years, longitudinally predicted positive changes in cognitive functions, well-being, sense of control, self-esteem and social relationships," he said.
Regular use of the computer, he added, was related to greater life satisfaction, and the positive effects of computer use on the participants' cognitive functioning and socio-emotional well-being did not come at a cost to their physical and mental health, he said.
"The smartphone is considered one of the biggest sources of distraction in our daily life now," added Dr Hartanto.
"We need to be smarter in using our smartphone so it won't negatively affect our daily productivity and social relationships."
The mobile phone is such a big part of our lives that some of us naturally worry if excessive use could increase the risk of tumours in the brain, head or neck.
After all, mobile phones emit a form of radiation from their antennae, which can be absorbed by body tissues.
But this radio-frequency (RF) radiation is actually a form of non-ionising radiation that differs from stronger (ionising) types of radiation, such as those from X-rays and ultraviolet light, which are known to increase cancer risk.
RF radiation is "not believed to be capable of causing genetic mutations in cells that lead to cancer formation", said Dr Wong Seng Weng, medical director and consultant medical oncologist at The Cancer Centre.
Also, the prevalence of mobile phone use is high and the incidence of brain cancer is low, he said.
However, that is not to say that excessive use is completely clear of harm.
The World Health Organisation's International Agency for Research on Cancer classifies electromagnetic radiation from mobile phones as possibly carcinogenic for the brain, though this issue is mired in controversy.
The agency's conclusion was based mostly on the large international Interphone study published in 2010, which showed that the top 10 per cent of mobile phone users (in terms of call time) had a 40 per cent increase in risk of developing gliomas, a type of brain tumour.
"There are, however, more than 30 studies done to date on the topic and the conclusions were often conflicting," said Dr Wong.
Just last November, the United States-based National Institutes of Health said their study showed that male rats exposed to RF radiation have an increased risk of developing schwannomas in the heart. Such cancers are very rare in humans, said Dr Wong.
The US Food and Drug Administration promptly disagreed with the conclusion, saying that available evidence does not support adverse health events in humans under current RF energy exposure limits, Dr Wong added.
It is possible that mobile-phone radiation may not cause cancer, but is capable of promoting cancer progression in the presence of other carcinogenic factors, he said.
What is clear is that there is no consistent evidence that RF radiation increases cancer risk in humans. (The most consistent health risks associated with cellphone use are distracted driving and vehicle accidents.)
Dr Wong believes the use of mobile phones is generally safe.
"However, of concern to me is the finding in the Interphone study that the deposition of radio-frequency energy in the brain of a child is twice that of an adult," he said.
"Perhaps, it is prudent to consider limiting the use of mobile phones for young children."
Also, if you would want to be very safe, you could reconsider certain practices that may increase your exposure, such as sleeping with your phone next to you or making calls in low signal environment, Dr Wong added.
In Singapore, the National Environment Agency (NEA) monitors international developments relating to studies on the effects of RF exposure on health.
Right now, more studies are being done to ascertain whether low levels of RF radiation would lead to any long-term adverse health impact.
In the meantime, individuals could take precautionary measures to reduce RF exposure by limiting the length of calls or using hands-free devices to keep mobile phones away from the head and body, said an NEA spokesman.
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