Mind & body, in brief

Short sight is not a fault in the lens at the front. The eyeball itself has grown too long, so the picture lands in front of the retina instead of on it [1][8].

A newborn's eye is too short for its own optics. It then grows until the picture lands sharply, and the retina steers that growth, sending signals that thicken or thin the layer behind it and rebuild the white outer wall [1].

About 27% of the world, 1.45 billion people, were short-sighted in 2010. Modelling puts it at 4.758 billion by 2050, 49.8% of everyone alive [1][6].

Children who spend more time outdoors become short-sighted less often. Across 31 studies of 380,215 Chinese children, more than two hours a day outdoors came with about a quarter lower odds, though the studies disagreed with each other a great deal [5].

In over 210,000 Chinese schoolchildren followed over time, 2 to 3 hours outdoors a day carried 10% lower risk of new short sight, and more than three hours carried 14% lower. More than three hours of daily reading carried 5% higher [4].

In chicks wearing lenses that blur distance, brighter light slowed the eye's growth in proportion to how bright it was, and dopamine in the retina rose with the brightness [3].

Blocking one family of dopamine receivers in those chicks, the D2-like family, removed most of the protection. Blocking the D1-like family did nothing [3].

A summer afternoon in Canberra, Australia was measured at about 90,000 lux. An indoor room lit by fluorescent tubes is around 500 lux [2].

Studies rarely measure being outdoors directly. Many score it as light above 1,000 lux, a cut-off the reviewers say can occasionally be reached indoors and has been argued over for years [2].

The International Myopia Institute's 2025 review concludes that the two-hours-a-day advice is well supported by the population studies. It also finds the evidence supports no guidance at all on how bright the light should be, for how long, or at what time of day [2].

The same review says the human data cannot yet separate whether bright light acts on the eye or simply marks being outside, where children also look at distant things and move about [2].

Why it matters. Watch for a trial that puts light meters on children and varies the brightness rather than the hours. That is the one design that could say whether the hours or the daylight does the work [2].

Forty-one adults ate two ultra-processed diets for two weeks each, in random order. The two menus were matched for taste, portion size served, total calories served and energy density. The only real difference was food texture, which sets how fast people eat. On the slower-textured menu they took in 369 fewer calories a day, and the gap held steady across all fourteen days [14]. A separate review lists faster eating as one of the routine features of ultra-processed food [19].

Why it matters. Both arms of the trial were ultra-processed, so whatever the label is picking up, a large part of it here was chewing speed.

In 2019 a US feeding trial found people ate about 500 calories a day more on an ultra-processed diet than an unprocessed one. Researchers have now gone back to the plate-by-plate records of those twenty adults. On the unprocessed diet people picked more low-calorie items, mostly fruit and vegetables. Their dinners came out 57% heavier and still held fewer calories, 719 against 830 [15]. Nobody had told them to choose that way.

Why it matters. The difference sat in what people reached for when offered a choice, which is a different thing to change than how much food is put in front of them.

Twenty-seven people aged 18 to 25 spent two weeks on a diet that was 81% ultra-processed and two weeks on one with none, matched for protein, fat, carbohydrate, fibre, added sugar and energy density. Afterwards each was offered a free buffet. Across the whole group there was no difference in how much they ate. Split by age, the 18 to 21-year-olds ate more after the ultra-processed fortnight and the 22 to 25-year-olds did not [16].

Why it matters. An effect that is real in late adolescents and absent in young adults vanishes entirely once the two are averaged into one number.

There is no accepted definition of ultra-processed food, and a critical review argues the published definitions predict different health risks from one another. Most of the evidence tying processing to obesity is observational, and the review calls those links weak and inconsistent. It also notes that in community trials people often did not manage to cut their intake, so the trial tested the advice rather than the food [17]. A scoping review separately links higher intake to depression, anxiety and attention problems, rising with the amount eaten [18].

Why it matters. Several governments are being asked to write dietary rules around a category whose boundary is still being argued over.

Eight randomised trials, 482 older adults, all doing resistance training two or three times a week for between 8 and 104 weeks. Half also took creatine, a compound found in meat and made by the body, which helps muscle produce short bursts of power. Against training alone it added a small gain in leg strength and lean tissue, and nothing measurable in the arms. In the trials running 32 weeks or less the gains were larger [20].

Why it matters. The extra is real and it is small, and the training is still the part carrying almost all of the result.

Fourteen trials of 528 older adults with sarcopenia, the age-related loss of muscle, were pooled to ask which training settings matter. The researchers pulled out sessions per week, load, number of weeks, sets, whether the programme got harder over time and whether people trained to failure. None of those explained why some programmes built muscle and others did not. The one thing that did was age: the trials that failed had recruited significantly older people [21].

Why it matters. The field went looking for the setting to change and found that who was recruited mattered more than any setting.

Twelve trials covering 518 older women with sarcopenia were pooled. Resistance training improved grip strength, walking speed, knee extension strength, a timed stand-and-walk test and a 30-second chair-stand count. It did not shift skeletal muscle mass index at all. Muscle mass is one of the measures the condition is defined by, and it is the one that did not move. Women who also carried obesity gained more knee strength than the rest [22].

Why it matters. Getting out of a chair is what the training bought, and the scan of how much muscle is present reports nothing happened.

Nine randomised trials, 496 people with sarcopenia, testing whether adding amino acids beats resistance training alone. Amino acids are the building blocks of protein; the trials used essential and branched-chain forms, leucine, and the derivative HMB. Grip strength, walking speed, a physical performance battery and a sit-to-stand test all improved with supplements added. Skeletal muscle mass did not. The reviewers graded the certainty of all of it as low to very low [23].

Why it matters. A large supplement trade rests on this question, and the evidence under it is rated near the bottom of the scale researchers use.

Long bed rest strips muscle fast, which is why countermeasures get tested there. A pooled analysis found that under the single heading of resistance training, plain resistance work produced no measurable gain in muscle volume. Flywheel training, which loads a muscle hard while it lengthens, and concurrent training, which mixes strength and endurance work, both produced large gains. Training three days a week worked; more than three days a week did not [24].

Why it matters. One heading covered three different things, and two of them did the work while the third did nothing.

A Bayesian network meta-analysis pooled 35 randomised trials of 2,331 older adults with sarcopenia, diagnosed by the European and Asian working-group criteria. Exercise combined with nutritional supplements ranked first for grip strength, walking speed and limb muscle mass, adding 3.69 kilograms of grip and 0.11 metres per second of walking speed [25]. A separate network analysis of 17 trials in 1,107 pre-frail older adults put elastic-band exercise top for grip, and a progressive programme with tai chi top for balance [62].

Why it matters. Both analyses are ranking whole programmes against each other, so neither can say which part of the winning programme won.

Muscle loss begins around age 35 and runs at 1% to 2% a year, rising to about 3% a year after 60. An adult who does no strength training can expect to lose four to six pounds of muscle a decade, usually replaced by fat [28]. It makes stairs and standing up harder and raises the risk of falls and fractures [27]. Researchers say the biggest health gain comes from starting from nothing, not from training harder [26].

Why it matters. The people with most to gain are the ones currently doing none, and they are the hardest group for any trial to recruit and keep.

Social isolation means having few contacts and can be counted. Loneliness is the feeling of not having enough, and has to be asked about. In 354,537 UK Biobank participants followed for a median 11.6 years, 38,103 developed cancer. After adjustment, isolation carried an 8% higher risk and loneliness carried none. The size of the isolation effect also differed strongly between men and women [29].

Why it matters. The two are routinely reported together as one risk factor, and here only one of them tracked the disease.

Six cohort studies covering 5,253,128 people, followed between four and 11.3 years, were pooled for heart disease and stroke. Together, isolation or loneliness carried a 17% higher risk. Split apart, people with a history of social isolation carried 39% higher risk, more than those reporting loneliness. The studies disagreed with one another a great deal [30]. A separate study of 8,046 Chinese adults aged 45 and over found loneliness alone carried 42.9% higher risk over seven years [63].

Why it matters. Two careful analyses put the bigger number on different halves of the same pair. Isolation looked worse in one of them and loneliness looked worse in the other.

In UK Biobank participants followed a median 11.6 years, 9,453 developed asthma as adults. Here it was loneliness that carried the risk, 27% higher, and social isolation showed nothing once other factors were adjusted for. The researchers also ran a Mendelian randomisation analysis, which uses inherited genetic differences to test whether a link is likely to be causal. It gave suggestive genetic support for feeling lonely and for taking part in fewer social activities [33].

Why it matters. Cancer pointed at isolation and asthma points at loneliness, so whatever these two questionnaires capture, they are not measuring one condition.

UK Biobank participants were matched into two equal groups, obese and not, and followed a median 12.4 years. Among the obese half, 18,280 developed a mental disorder recorded in primary care or hospital records. Compared with the least lonely, the moderately lonely carried 37% higher risk and the loneliest 73% higher, rising steadily across the scale. The same pattern appeared for social isolation [31].

Why it matters. The risk climbed step by step as loneliness rose. That pattern makes a cause more plausible, and it still does not prove one.

Isolation and loneliness were each linked to thinning bone and to fractures in a large cohort, with hazard ratios of about 1.12 and 1.19 for osteoporosis and 1.11 and 1.18 for breaks. Inherited risk did not change the pattern. The researchers then tested what the link travelled through, and found frailty and body-wide inflammation carried part of it, anywhere from under 1% to about 37% of the total, depending on which pairing was measured [32].

Why it matters. A range running from 1% to 37% is the honest answer here, and it is wide enough to mean the route is not yet known.

A review pulls together what happens in animals kept alone: disrupted signalling between nerve cells, a stress-hormone axis running differently, and changes in how the body handles fuel. It connects long-term isolation to metabolic syndrome and heart disease through oxidative stress, inflammation, faulty mitochondria and poor clearing-out of damaged cell parts [34]. A review of the human evidence, published separately, says the field still cannot say whether loneliness is a cause of poor health, a companion of it, or a result [35].

Why it matters. The animal work has a mechanism and the human work has the numbers, and neither one can supply what the other is missing.

Twenty-seven people took part: ten with breast cancer, twelve with prostate cancer and five postmenopausal women, all having at least two moderate-to-severe hot flushes a day. Each wore a wrist device cooled to 47F for two weeks and an identical sham that only blew air for two weeks, without knowing which was which. Severe episodes fell 46% against baseline and all daily flushes fell 18%. Nobody dropped out and no side effects were reported [36].

Why it matters. Hormone-blocking cancer treatment produces the same flushes as menopause, and the drug options for both carry risks a cold wristband does not.

Sixty-nine postmenopausal women were split by whether they had ever had hot flushes or night sweats. Researchers pushed a fine electrode into a leg nerve to count the bursts of signal running out to the blood vessels, which is one of the main things setting blood pressure. Resting blood pressure was the same in both groups. The flush group fired more bursts per hundred heartbeats, 53 against 44, with a slower resting heart rate and more variation between beats [37].

Why it matters. Hot flushes are handled as a comfort problem, and this measures a difference in the nerve traffic that helps set blood pressure.

Ninety-nine women recorded their hot flushes and their sleep every day for a week, separating daytime, evening and overnight episodes. Two different things turned out to matter. Within a woman, more severe flushes in the evening predicted a longer time to fall asleep that night, while more frequent flushes during the night predicted worse sleep quality. Daytime episodes predicted neither [38].

Why it matters. A study counting only night sweats would miss the evening half of this, and severity and frequency are turning out to do different jobs.

Menopause is the permanent end of periods, defined as twelve months without one, and most often arrives between ages 45 and 56 [40]. A flush is not simply the hormone drop. As the ovaries run out of follicles, oestradiol and progesterone fall, and the brain's control network rewires around three signalling systems called kisspeptin, neurokinin B and GABA. That changes the pulsing of the hormone driving the cycle, and produces the flushes [39]. Inflammation, oxidative stress and failing mitochondria run alongside it [39].

Why it matters. Naming that machinery is what makes a non-hormonal drug possible, because it supplies a target that is not oestrogen.

Antihistamines fail most people with long-term itch, and the reason is that histamine is one messenger among many. Mast cells, immune cells sitting beside nerve endings in the skin, also release enzymes, signalling proteins, fat-based messengers and nerve growth factors that make sensory nerves fire more easily. Those nerves answer back with their own chemicals, which switch the mast cells on again. A review proposes treating the two together as one unit that feeds itself [41].

Why it matters. It explains a very common experience, that the cream and the tablet do nothing, as a property of the wiring rather than a failure to use them properly.

In eczema, a signalling protein called IL-31 lands on sensory nerves in the skin and turns up two channels that make those nerves fire more readily. How much of its receiver sits on the nerves tracks how badly patients rate their own itch. In affected skin that receiver stays high after the visible inflammation has settled, which researchers describe as a memory held in the nerve rather than in the skin [42].

Why it matters. It supplies a mechanism for the itch that outlasts the rash, and a reason that clearing the rash can leave someone still scratching.

Gut pain and itch both feel bad and both resist treatment, and it was unclear whether the brain separates them. In mice, researchers found two different groups of cells in the basolateral amygdala, an almond-sized region that handles threat. One responded to gut pain, one to itch, and they ran to different destinations, the hypothalamus and the striatum. Two different genes were switched on in the two groups, and silencing each one damped only its own sensation [43].

Why it matters. Separate circuits mean a drug could in principle quiet itch without touching pain, which the drugs now in use cannot do.

Old mice scratched no more than young ones when left alone, but scratched far more when lightly touched, a state called alloknesis. Their urine carried more serotonin, and their sensory nerve bundles and spinal cords carried more of one serotonin receiver, 5-HT7. Blocking that receiver reduced the touch-triggered scratching [44]. Long-term itch with no cause ever identified is common in older people, and a systematic review says its mechanisms are still poorly understood, with several competing explanations [45].

Why it matters. It points at one specific target in a complaint usually written off as dry skin and age.

142 people were followed from 2020: 35 never infected, 54 acutely ill, 24 recovered and 28 with long COVID. More than 180 days after infection the long COVID group still showed switched-on inflammatory pathways and signs of exhausted T-cells, compared with people who had recovered from the same virus. A second group recruited in 2023 and 2024 showed the same pattern [46]. A review of studies to August 2025 reports the same persistent activation, plus antibodies aimed at the body's own tissue [50].

Why it matters. Two separate groups of patients three years apart landing on the same signature is what turns a hypothesis into a candidate test.

A review argues that a single cell type explains most of long COVID: the macrophage, a large immune cell that swallows debris and raises the alarm. The case is that these cells get locked into an inflamed state by leftover viral protein, by reservoirs in the gut, and by chemical marks laid on their DNA that keep the inflammatory genes readable. The authors present it as a framework for testing rather than as an established finding [47].

Why it matters. Naming one cell gives drug developers something to aim at, which the long list of competing causes does not.

A second review puts the cause in the endothelium, the single layer of cells lining every blood vessel. The argument is that infection pushes those cells into senescence: alive, no longer dividing, and leaking inflammatory and clot-promoting chemicals. At the barrier around the brain, in the gut and in muscle, that could account for the symptoms, and a poorly working immune system never clears the senescent cells [48]. Long COVID and ME/CFS share many of these features, with the balance between them unsettled [51].

Why it matters. Three reviews in the same month name three different central causes, which is what an unsettled field looks like from outside it.

A 2024 estimate put 400 million people worldwide living with long COVID, at an annual economic cost near one trillion US dollars. Researchers are now working backwards from who develops it, testing antivirals and immune drugs [49]. In 161 patients assessed six to nine months on, those who had run higher peak temperatures and lower blood oxygen during the acute infection carried more of one inflammatory assembly, the NLRP3 inflammasome, and more of the chemicals it releases [60].

Why it matters. A measurement taken during the first illness that predicts the later one is the closest thing this field has to a handle.

Hair cells are the sensory cells of the inner ear, and their death has long been treated as the cause of hearing loss. A review argues the order is often the other way round. The connections between hair cells and the hearing nerve, and the fine bristles on top of the cells, are typically lost first, while the cells themselves are still there but working badly. On that reading, hair cell loss is frequently a later consequence [52].

Why it matters. It moves the moment worth intervening earlier, to a point when the cells are still alive to be helped.

Outer hair cells are the ear's amplifier: they physically push back on the sound wave, which is what gives hearing its enormous range. For that to work their tallest bristles must stay attached to a gel-like sheet above them, through a structure nobody had fully identified. Researchers now name a protein, TMEM145, as its core element. Mice bred without it lost two known partner proteins from the bristles, the bundle came free of the sheet, and the animals were profoundly deaf with no amplification at all [53].

Why it matters. It names one protein whose failure would look, in a clinic, like ordinary hearing loss with no cause found.

The World Health Organization reviewed everything published between 2010 and August 2025 on vaccines, the mercury-based preservative thiomersal, and autism. On thiomersal the count was tied: nine papers reported no link, nine reported one. Graded for design quality, all nine reporting a link came from one group of authors in the United States and all nine were rated very low strength of evidence and high risk of bias. On vaccines generally, 17 of 19 studies found no link, covering nearly 800,000 children in six countries [54].

Why it matters. Counting papers gives a tie and weighing them does not, and that distance is where most of the public argument has been sitting.