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A glass of tart cherry juice before bed has a famous number attached to it: 84 extra minutes of sleep. It has been making the rounds online.

We read the study behind it. The number is real, as reported. The catch is everything around it.

Read the 2018 study yourself (free full text)

This is a look-back at a 2018 pilot study, not new research. The news peg is the viral post, not the science.

Also on the calendar: clocks fall back at 2 a.m. on Sunday, Nov. 1. Hawaii and most of Arizona stay put.

The famous 84 minutes comes from a 2018 pilot study of just 8 adults with insomnia. They were 50 or older, and people with diabetes were not allowed in.

Each person spent one night in a sleep lab per drink: once after two weeks of tart cherry juice, once after two weeks of a look-alike placebo drink. Sleep was measured with polysomnography, the full overnight lab sleep test. On the cherry night, they slept 84 minutes longer on average.

That is one lab night per drink, for 8 people, with no practice night in the lab first.

The study dose was two 8-ounce glasses a day. The study dose had about 54 grams of sugar a day, based on the current label of the brand used. That is about 280 calories a day, too. The placebo drink also contained sugars, in an amount the paper does not report.

Funded by the Cherry Marketing Institute and the NIH. The institute also supplied the juice.

The paper says the institute had nothing to do with the design of the trial.

Most other measures, like time awake during the night or how fast people fell asleep, did not change in a meaningful way. Scores on an insomnia severity questionnaire did not clearly change either.

Sleep efficiency, the share of time in bed actually spent asleep, also did not clearly change. Our own reading: that pattern hints people may simply have spent more time in bed on the cherry night. The paper does not report time in bed, so we can't check.

Also interesting: 3 of the 11 people first enrolled turned out to have sleep apnea on the lab test. Insomnia-like nights are not always insomnia. (More on sleep apnea below.)

Tart cherry juice has been tested a few more times, and the picture gets less exciting.

An earlier 2010 study (also a look-back) of 15 adults 65 and older found people reported about 17 fewer minutes awake per night than with a sugar-matched placebo. Total sleep did not change, and the juice maker paid for the study. Those results came from sleep diaries, not lab measurements. The authors called the effects modest, and participants still showed insomnia afterward.

A 2012 study (look-back) in 20 healthy young adults without sleep complaints found a small rise in a melatonin marker and about 40 more minutes of sleep tracked by a wrist device. Their own sleep diaries showed no difference. The company that made the cherry concentrate donated it.

Cherries do contain some melatonin, but far less than supplements. The melatonin in a day of tart cherry concentrate in that 2012 study was about 85 micrograms. Typical melatonin supplements studied for sleep start around 500 micrograms. Why tart cherry might help, if it does, is unclear.

A review published in September 2026 pooled 10 trials with 294 people, from athletes to healthy adults to people with insomnia. Overall, tart cherry did not clearly beat placebo, and the authors rated the certainty of that evidence as very low. The only positive signal came from the two small insomnia studies above, and the authors call it preliminary.

One caveat on the review itself: its lead author also authored 3 of the 10 included trials.

The honest answer: the evidence does not single anyone out. The only hint of a benefit came from two small studies in older adults with insomnia, and both left out people with diabetes. For anyone counting sugar, 54 grams a day is not a rounding error.

Tart cherry juice is not part of clinical insomnia guidelines. If sleep problems keep going, the treatment with the strongest evidence for chronic insomnia is CBT-I, a structured talk-and-habits therapy.

The claim: a viral post citing SPECT scans says caffeine cuts blood flow to the brain by 30%. Versions of this claim add that it ages the brain.

What's true: caffeine really does narrow blood vessels in the brain. In three MRI studies we read in full, a single dose of about 180 to 250 mg, roughly two cups of coffee, lowered resting brain blood flow by about 20 to 35% on average. In one study of 45 adults, a 250 mg dose cut it by about a quarter on average.

What about the scans? The one caffeine SPECT study we found saw a small drop of 6 to 8% that was not statistically significant, and it was partly funded by a coffee industry science group.

Regular drinkers adapt: regular coffee drinkers partly adapt. Skip your usual coffee and brain blood flow can bounce above normal.

Less flow, starving brain? Lower blood flow is not the same as a starving brain. In one small study of 10 people, blood flow fell by about a third after 200 mg, but the brain's oxygen use did not fall measurably.

"Ages the brain"? Claims that caffeine "ages the brain" go beyond the evidence. No study we found shows that. The MRI paper often linked to that claim says nothing about aging.

While we're on caffeine: how long does it stick around? Caffeine's half-life is the time your body takes to clear half of it. In healthy adults it is often around 3 to 7 hours, and it can be shorter or much longer from person to person. Smoking speeds caffeine clearance. Birth control pills, pregnancy and liver disease slow it.

In a small 2013 home study (a look-back), a big 400 mg dose taken 6 hours before bed cut measured sleep by about an hour. Most people did not feel that in their sleep diaries. That was 12 people, measured with a headband device, and the headband's maker funded the study.

A 2023 review of 24 controlled studies found caffeine cut sleep by about 45 minutes on average. For a typical cup of coffee, the effect stopped being measurable when the cup came roughly 9 hours before bed. That is a statistical cutoff, not a proven "safe" time, and people vary.

Verdict: Real effect, overstated story. Caffeine narrows brain blood vessels for a few hours, so measured blood flow drops. Researchers have not shown that this ages the brain.

This is not a letter from a specific reader. It is a question that comes up a lot online, often right after a diagnosis. Here is what the research we checked can and can't say.

Sleep apnea isn't only a weight problem. It's less common in lean, younger adults, but it does happen.

In a long-running Wisconsin study, about 1 in 100 men aged 30 to 49 with a normal BMI had moderate or worse sleep apnea, compared with about 1 in 6 men that age with obesity (a BMI of 30 to 39.9). Those are model-based estimates from a mostly white cohort, and the study had no data on people under 30.

Anatomy plays a role. In a study of patients in Sydney and Hong Kong, Chinese patients had smaller jaws and a shorter skull base, while white patients with the same severity tended to weigh more. That was a sleep clinic study, not a sample of the general population.

In a large US study of older adults, Chinese Americans had higher odds of sleep apnea than white Americans at every weight level.

Most cases go unrecognized: in that same study, fewer than 1 in 6 people with moderate or worse sleep apnea said they had ever been diagnosed.

Women may not fit the stereotype either. Reviews note they're less likely to report snoring and more likely to report fatigue, trouble sleeping, morning headaches or low mood.

One honest gap: we found no study that puts a number on sleep apnea in fit or athletic people specifically, so "fit" does not come with a statistic here.

Loud snoring, pauses in breathing someone notices, or daytime sleepiness that doesn't add up are worth raising with a doctor, whatever your size.

Be honest: have you ever tried a sleep trick because a post went viral?

A. Yes, and I'm still doing it.
B. Yes, once. Never again.
C. No, I just bookmark them.

Reply with A, B or C. This is a conversation starter, not a scientific survey. A purple cherry juice mustache counts as a yes.

Losso JN, Finley JW, Karki N, Liu AG, Prudente A, Tipton R, Yu Y, Greenway FL (2018, look-back). Pilot Study of Tart Cherry Juice for the Treatment of Insomnia and Investigation of Mechanisms. Am J Ther 25(2): e194-e201. https://doi.org/10.1097/MJT.0000000000000584 PMID 28901958, PMCID PMC5617749. Randomized, placebo-controlled crossover pilot; 11 randomized, 8 analyzed. Registered: NCT01669317. Funded by the Cherry Marketing Institute and the NIH. The institute also supplied the juice.

Sugar estimate: USDA FoodData Central, Indian Summer Montmorency Tart Cherry Juice (FDC 2084688), current label: 27 g sugars per 8 fl oz, doubled for the study dose. Not the label of the 2014/15 study batch.

Pigeon WR, Carr M, Gorman C, Perlis ML (2010, look-back). Effects of a Tart Cherry Juice Beverage on the Sleep of Older Adults with Insomnia: A Pilot Study. J Med Food 13(3): 579-583. https://doi.org/10.1089/jmf.2009.0096 PMCID PMC3133468. Self-reported outcomes (sleep diaries, questionnaire). CherryPharm, Inc., the maker of the juice, funded the study in its entirety.

Howatson G, Bell PG, Tallent J, Middleton B, McHugh MP, Ellis J (2012, look-back). Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality. Eur J Nutr 51(8): 909-916. https://doi.org/10.1007/s00394-011-0263-7 Healthy adults aged 18 to 40; CherryActive donated the concentrate.

Sinclair JK, Baker L, Bottoms LM (2026). Effects of Tart Cherry (Prunus cerasus) Supplementation on Overall Sleep Quality, Melatonin, and Inflammatory Biomarkers: A Systematic Review and Meta-Analysis. Recent Progress in Nutrition 6(3): 024. https://doi.org/10.21926/rpn.2603024 Published Sept. 30, 2026. Preregistered (PROSPERO CRD420251229156). Funding: not applicable; the authors declare no conflicts.

Addicott MA et al. (2009, look-back). The effect of daily caffeine use on cerebral blood flow: How much caffeine can we tolerate? Hum Brain Mapp 30(10): 3102-3114. https://doi.org/10.1002/hbm.20732 Funding: NIH.

Vidyasagar R et al. (2013, look-back). The effect of black tea and caffeine on regional cerebral blood flow measured with arterial spin labeling. J Cereb Blood Flow Metab 33(6): 963-968. https://doi.org/10.1038/jcbfm.2013.40 Funded by Unilever R&D; two co-authors were Unilever employees.

Perthen JE et al. (2008, look-back). Caffeine-induced uncoupling of cerebral blood flow and oxygen metabolism: a calibrated BOLD fMRI study. NeuroImage 40(1): 237-247. https://doi.org/10.1016/j.neuroimage.2007.10.049 Funding: NIH. No placebo arm.

Nehlig A, Armspach JP, Namer IJ (2010, look-back). SPECT assessment of brain activation induced by caffeine: no effect on areas involved in dependence. Dialogues Clin Neurosci 12(2): 255-263. https://doi.org/10.31887/DCNS.2010.12.2/anehlig Funding includes a grant from PEC-ISIC, a coffee industry science body.

Temple JL et al. (2017). The Safety of Ingested Caffeine: A Comprehensive Review. Front Psychiatry 8: 80. https://doi.org/10.3389/fpsyt.2017.00080

Grzegorzewski J et al. (2022). Pharmacokinetics of Caffeine: A Systematic Analysis of Reported Data (title shortened). Front Pharmacol 12: 752826. https://doi.org/10.3389/fphar.2021.752826

Drake C, Roehrs T, Shambroom J, Roth T (2013, look-back). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med 9(11): 1195-1200. https://doi.org/10.5664/jcsm.3170 Funded by an investigator-initiated grant from Zeo Inc, maker of the headband device used; one co-author was a former Zeo executive.

Gardiner C et al. (2023). The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Med Rev 69: 101764. https://doi.org/10.1016/j.smrv.2023.101764 Preregistered (PROSPERO CRD42021267812). The authors report no conflicts of interest.

Peppard PE, Young T, Barnet JH, Palta M, Hagen EW, Hla KM (2013, look-back). Increased prevalence of sleep-disordered breathing in adults. Am J Epidemiol 177(9): 1006-1014. https://doi.org/10.1093/aje/kws342 Wisconsin Sleep Cohort; model-based estimates. Funding: NIH.

Chen X et al. (2015, look-back). Racial/ethnic differences in sleep disturbances: the Multi-Ethnic Study of Atherosclerosis (MESA). Sleep 38(6): 877-888. https://doi.org/10.5665/sleep.4732 Cross-sectional; adults aged 54 to 93. Funding: NHLBI/NIH.

Lee RWW et al. (2010, look-back). Differences in craniofacial structures and obesity in Caucasian and Chinese patients with obstructive sleep apnea. Sleep 33(8): 1075-1080. https://doi.org/10.1093/sleep/33.8.1075 Sleep clinic patients in Sydney and Hong Kong.

Bonsignore MR, Saaresranta T, Riha RL (2019). Sex differences in obstructive sleep apnoea. Eur Respir Rev 28: 190030. https://doi.org/10.1183/16000617.0030-2019 Narrative review; no conflicts of interest.

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The Sleep News provides general information, not personal medical advice. If sleep problems persist or affect safety, seek qualified medical care.

Forward this to a friend who sleeps badly.