Do screens and too little outdoor light cause short-sightedness?
Screens are probably not the main culprit; too little time outdoors and academic pressure are better-supported causes. Make sure your child spends enough time outside every day, especially at a young age.
Short-sightedness in children has increased sharply over recent decades. The most plausible explanation is the combination of too little time outdoors and a lot of close-up work. The strongest evidence concerns time spent outside: each extra hour per day outdoors lowered the chance of becoming short-sighted by roughly 10 percent. Studies in people, including ones that can properly separate cause from effect, confirm this is a genuine relationship, not just a coincidence.
Screens themselves probably play a smaller role than you might expect. Many studies combined found no clear link between screen use and short-sightedness. Screen use and little time outdoors tend to go hand in hand, which makes it difficult to measure their effects separately. More recent studies do point to a trend, but screen time is rarely measured accurately.
Close-up work, such as reading and writing, has been debated for decades. Early studies found hardly any link. More recent studies find a raised risk when the viewing distance is less than 30 centimetres and when close-up viewing continues uninterrupted for more than 30 minutes. How close-up work is measured turns out to strongly determine whether any link is found at all. More years of schooling and higher academic pressure have been causally connected to short-sightedness through genetic research.
That outdoor light is the key factor is also clear from the fact that indoor sports offer no protection. It is not about moving around, but about daylight. The lockdowns during the Covid-19 pandemic illustrate this strikingly: in 6-year-old children in China, the proportion with short-sightedness rose from 5.7 percent to 21.5 percent in 2020, compared with the years 2015 to 2019. In children aged 9 and older the effect was much smaller. This suggests that young children are especially vulnerable during a sensitive period of eye development. A historical example supports this: in Arctic Inuit communities, short-sightedness rose from less than 3 percent to more than 50 percent in new generations after the Second World War, coinciding with a forced shift to indoor living and intensive schoolwork.
This answer draws on several large studies in children, including studies where participants were assigned to groups by chance and genetic research that can separate cause from effect more reliably than ordinary observation. The evidence is strongest for time spent outdoors. For screen use alone, the evidence is thin and contradictory. The Covid-19 lockdown data come from a single Chinese study with methodological limitations, such as the absence of specific eye measurements, so those findings deserve some caution.
Do your eyes age faster than the rest of your body?
The lens of the eye ages noticeably early and quickly, but whether your eyes as a whole age faster than the rest of your body has not been demonstrated. The retina actually reveals a great deal about your overall health, so the two track more closely together than you might think.
Will I live longer with more social contact?
More social contact is linked to a longer life, but the effect is far more specific than you might think: the type of contact and your sex make the difference, and quality counts more than quantity.
How do I keep my eyes healthy and prevent cataracts or macular degeneration?
Protect your eyes with UV-filtering glasses, a diet rich in vegetables and fruit, good diabetes management and regular eye check-ups. If cataracts have advanced significantly, surgery is the only proven solution.
How do I know whether my fatigue is caused by my thyroid?
Thyroid blood tests can rule out or confirm whether your thyroid is the cause, but a mildly abnormal TSH alone does not explain fatigue and treating it often does not help. In Hashimoto's, symptoms can persist even when your values are normal.
Does exercise help with Parkinson's disease?
Exercise demonstrably helps with Parkinson's disease: motor symptoms decrease and quality of life improves. Dance and aquatic exercise have the strongest evidence base; flexibility training offers little benefit. Discuss with your healthcare provider which form best suits your situation.
What are the symptoms of an underactive thyroid?
An underactive thyroid produces vague complaints such as fatigue, weight gain and cold intolerance, but the diagnosis can only be made through a blood test. If you have recognised several complaints for a while, discuss them with your general practitioner.