What the research says

Hot nights

No meta-analysis yet, but a systematic review of 36 studies and wearable data from hundreds of thousands of people agree: hotter nights mean shorter, worse sleep, about 15–17 minutes less on very hot nights. Most homes can heat but not cool, which is why only warm nights count in the forecast.

No meta-analysis found.

1. Systematic review36 articles (no pooling: designs too varied)

   Chevance G, Minor K, Vielma C, et al. (2024). A systematic review of ambient heat and sleep in a warming climate. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2024.101915

   Higher outdoor or indoor temperatures are generally linked to worse sleep quality and quantity, more so in the hottest months, regions and vulnerable groups.

2. Large study, not a meta-analysis317,758 users, about 165 million nights

   Lechat B, Toson B, Scott H, et al. (2026). How do we sleep while our beds are burning? High ambient temperatures are associated with substantial sleep loss. Sleep. doi.org/10.1093/sleep/zsaf323

   At the 99th vs 50th temperature percentile (27.3 °C vs 12.2 °C), sleep was 15.2–16.9 min shorter; risk of sleeping under 6 h rose by 40–43%.

3. Large study, not a meta-analysis214,445 participants, about 23 million days

   Li A, Luo H, Zhu Y, et al. (2025). Climate warming may undermine sleep duration and quality in repeated-measure study of 23 million records. Nature Communications. doi.org/10.1038/s41467-025-57781-y

   Each 10 °C rise in daily mean temperature: 20.1% higher odds of insufficient sleep and 9.67 min less total sleep.

4. Large study, not a meta-analysis47,628 adults, more than 7 million sleep records, 68 countries

   Minor K, Bjerre-Nielsen A, Jonasdottir SS, et al. (2022). Rising temperatures erode human sleep globally. One Earth. doi.org/10.1016/j.oneear.2022.04.008

   Higher temperatures erode sleep; suboptimal temperatures are projected to cost 50–58 hours of sleep per person per year by 2099.

Day of the week

People sleep later and longer on weekends: up to an hour more in older teenagers and 20–35 minutes more in adults, in pooled data and in 73 million tracked nights. A specific “Sunday night” effect has no study behind it, so the forecast only rewards nights before a day off.

1. Meta-analysis79 studies in the meta-analysis (18 on weekday vs weekend)

   Galland BC, Short MA, Terrill P, et al. (2018). Establishing normal values for pediatric nighttime sleep measured by actigraphy: a systematic review and meta-analysis. Sleep. doi.org/10.1093/sleep/zsy017

   At ages 15–18, total sleep on weekends or non-school days was 56 min longer; sleep onset about 1 h and wake-up about 2 h later.

2. Meta-analysis41 surveys

   Gradisar M, Gardner G, Dohnt H (2011). Recent worldwide sleep patterns and problems during adolescence: a review and meta-analysis of age, region, and sleep. Sleep Medicine. doi.org/10.1016/j.sleep.2010.11.008

   Weekend bedtimes were 2+ hours later worldwide, with more total sleep.

3. Meta-analysis37 studies

   Rodríguez Ferrante G, Lee F, Leone MJ (2024). Effects of school start time and its interaction with the solar clock on adolescents' chronotype and sleep: a systematic review and meta-analysis. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2024.101988

   Later school start times were linked to longer weekday sleep, later sleep timing and less social jetlag.

4. Meta-analysis30 studies, 92,977 data points

   Olds T, Blunden S, Petkov J, Forchino F (2010). The relationships between sex, age, geography and time in bed in adolescents: a meta-analysis of data from 23 countries. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2009.12.002

   Time in bed fell by 14 min per year of age on school days and 7 min on non-school days.

5. Large study, not a meta-analysis116,879 adults, about 73 million nights

   Scott H, Lechat B, Sansom K, et al. (2025). Variations in sleep duration and timing: weekday and seasonal variations in sleep are common in an analysis of 73 million nights from an objective sleep tracker. Sleep. doi.org/10.1093/sleep/zsaf099

   Sleep was 20–35 min longer on weekends; bedtime 30–40 min and wake-up 60–80 min later.

Clock changes

No meta-analysis has pooled sleep data around clock changes yet. Large tracker studies agree on the night itself: about an hour less sleep when clocks go forward in spring and about half an hour more when they go back in autumn, with some catch-up in the following days.

No meta-analysis found.

1. Large study, not a meta-analysis11,780 adults

   de Lange MA, Richmond RC, Birnie K, et al. (2025). The effects of daylight saving time clock changes on accelerometer-measured sleep duration in the UK Biobank. Journal of Sleep Research. doi.org/10.1111/jsr.14335

   Spring: sleep on the clock-change night 65 min shorter (95% CI −72 to −58). Autumn: 33 min longer (27–39).

2. Large study, not a meta-analysis24,250 wearable users, 10,350,760 sleep episodes

   Heacock RM, Capodilupo ER, Czeisler MÉ, et al. (2022). Sleep and Alcohol Use Patterns During Federal Holidays and Daylight Saving Time Transitions in the United States. Frontiers in Physiology. doi.org/10.3389/fphys.2022.884154

   Significant differences in sleep compared with baseline on most clock-change transitions.

3. Systematic review157 studies, 36 countries (no pooling: data too varied)

   Steponenaite A, Wallraff JP, Wild U, et al. (2026). A systematic review of epidemiological studies into daylight-saving time & health identifying beneficial & adverse effects. European Journal of Epidemiology. doi.org/10.1007/s10654-026-01372-8

   Standard time may be linked to shorter winter sleep; limited studies prevent clear conclusions on other sleep measures.

4. Systematic review27 studies (no pooling)

   Romigi A, Franco V, Scoditti E, et al. (2025). The effects of daylight saving time and clock time transitions on sleep and sleepiness: a systematic review. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2025.102161

   The switch to DST was linked to worse sleep duration and quality and more sleepiness, especially in evening types; findings were heterogeneous.

Big night-time events

There is no meta-analysis, but large tracker datasets show clear one-night effects: 13–16 minutes less sleep after the Brexit vote and the 2016 US election, and bedtimes about an hour and a half later on New Year’s Eve. The forecast uses a hand-made calendar of such nights.

No meta-analysis found.

1. Large study, not a meta-analysis10.5 million sleep records from more than 69,000 app users

   Anýž J, Bakštein E, Dudysová D, et al. (2019). No wink of sleep: Population sleep characteristics in response to the brexit poll and the 2016 U.S. presidential election. Social Science & Medicine. doi.org/10.1016/j.socscimed.2018.12.024

   Mean sleep fell by 16 min 21 s in the UK after the Brexit vote and by 12 min 49 s in the US after the 2016 election.

2. Large study, not a meta-analysis24,250 wearable users, 10,350,760 sleep episodes

   Heacock RM, Capodilupo ER, Czeisler MÉ, et al. (2022). Sleep and Alcohol Use Patterns During Federal Holidays and Daylight Saving Time Transitions in the United States. Frontiers in Physiology. doi.org/10.3389/fphys.2022.884154

   On New Year’s Eve sleep onset was 88.9 min later, wake time 78.1 min later, and alcohol use 138% more common.

Ramadan

During Ramadan, night-time sleep is consistently shorter (by about 0.8 hours in the largest meta-analysis) and later, with more daytime napping. The meta-analyses are small and mostly in young men and athletes, so the effect on whole populations is less certain. The forecast applies it in Muslim-majority countries.

1. Meta-analysis24 studies; 646 participants; 12 countries

   Faris MAE, Jahrami HA, Alhayki FA, et al. (2020). Effect of diurnal fasting on sleep during Ramadan: a systematic review and meta-analysis. Sleep and Breathing. doi.org/10.1007/s11325-019-01986-1

   Total sleep time fell from 7.2 h to 6.4 h (Hedges’ g −0.43); daytime sleepiness changed negligibly.

2. Meta-analysis18 papers; 298 participants

   Trabelsi K, Ammar A, Glenn JM, et al. (2022). Does observance of Ramadan affect sleep in athletes and physically active individuals? A systematic review and meta-analysis. Journal of Sleep Research. doi.org/10.1111/jsr.13503

   Sleep duration decreased (g −0.766); sleep quality score worsened from 4.05 to 5.35; daytime naps got longer.

3. Meta-analysis13 articles

   Trabelsi K, Bragazzi N, Zlitni S, et al. (2020). Observing Ramadan and sleep-wake patterns in athletes: a systematic review, meta-analysis and meta-regression. British Journal of Sports Medicine. doi.org/10.1136/bjsports-2018-099898

   Total sleep time decreased (effect size −0.97); daytime sleepiness unchanged.

4. Meta-analysis14 studies

   El-Jaziz A, Lotfi S (2025). Sleep Patterns Among Athletes and Non-Athletes During Ramadan intermittent fasting: Systematic Review, Meta-Analysis and Meta-Regression. Annali di Igiene. doi.org/10.7416/ai.2025.2675

   Sleep duration and efficiency were negatively affected; latency and disturbance were not.

5. Large study, not a meta-analysis24,541 adults in 27 countries

   Khan MAB, BaHammam AS, Amanatullah A, et al. (2023). Examination of sleep in relation to dietary and lifestyle behaviors during Ramadan: A multi-national study using structural equation modeling among 24,500 adults amid COVID-19. Frontiers in Nutrition. doi.org/10.3389/fnut.2023.1040355

   Sleeping 7–9 h during Ramadan was associated with physical activity and plant protein intake; smoking with worse sleep.

Air pollution

Meta-analyses covering more than four million people find that more fine particles (PM2.5) and NO2 go with roughly 6–30% higher odds of poor sleep per 10 µg/m³, and with more severe sleep apnea. Almost all of it is about long-term exposure, so the forecast gives polluted nights only a small weight.

1. Meta-analysis11 studies; 3,328,183 participants

   Cao Z, Shi X, Sun L, et al. (2025). Association between exposure to air pollution and risk of Dyssomnia: a systematic review and meta-analysis. International Archives of Occupational and Environmental Health. doi.org/10.1007/s00420-025-02137-8

   Odds of sleep problems per 10 µg/m³: PM2.5 1.29, PM10 1.13, NO2 1.06, O3 1.16; SO2 not significant.

2. Meta-analysis25 studies; at least 1,262,210 adults

   Wang M, Cho Y, Li J (2025). Air pollution and sleep health in middle-aged and older adults: A systematic review and meta-analysis. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2025.102136

   Long-term exposure, per 10 µg/m³: PM2.5 OR 1.27, PM1 1.37, PM10 1.10; NO2 (per 5 µg/m³) 1.07; ozone not significant.

3. Meta-analysis20 studies (13 pooled)

   He Y, Wang S, Zhang T, et al. (2026). Does short- and long-term exposure to air pollution affect the risk of obstructive sleep apnea? A systematic review and meta-analysis. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2025.102225

   Per 10 µg/m³ PM2.5, the apnea-hypopnea index rose 2.25% short-term and 13.33% long-term (high certainty).

4. Meta-analysis10 studies

   Zhao Y, Zhang S, Guo L, et al. (2024). Association between Air Pollutants and the Risk of Sleep Disorders: A Systematic Review and Meta-analysis. Aerosol and Air Quality Research. doi.org/10.4209/aaqr.230197

   Per 10 µg/m³: PM2.5 OR 2.50 (an outlier compared with other meta-analyses), PM10 1.15, NO2 1.36.

5. Meta-analysis12 studies (4 pooled)

   Alrahbeni T, Gupta JK, Alkhouri A, et al. (2024). Association of air pollution with risk and severity of obstructive sleep apnea: A systematic review and meta-analysis. Neurotoxicology. doi.org/10.1016/j.neuro.2024.04.005

   No significant link with sleep apnea risk (PM2.5 OR 0.987, NO2 1.095), though several studies linked pollution to greater severity.

Pollen and hay fever

People with hay fever consistently report worse sleep, more insomnia and snoring, and more daytime sleepiness, in data covering millions of people; treating the nose improves sleep in trials. The studies are about having hay fever rather than daily pollen counts, so the forecast only flags days with high pollen.

1. Meta-analysis27 articles; 240,706,026 patients (19,444,043 with allergic rhinitis)

   Liu J, Zhang X, Zhao Y, et al. (2020). The association between allergic rhinitis and sleep: A systematic review and meta-analysis of observational studies. PLoS One. doi.org/10.1371/journal.pone.0228533

   Worse sleep quality, more sleep medication and lower sleep efficiency; associated with insomnia, snoring, sleep apnea and daytime sleepiness. Sleep duration did not differ. Certainty low to very low.

2. Meta-analysis49 studies; 18,269,265 individuals

   Safia A, Elhadi UA, Karam M, et al. (2024). A meta-analysis of the prevalence and risk of mental health problems in allergic rhinitis patients. Journal of Psychosomatic Research. doi.org/10.1016/j.jpsychores.2024.111813

   Among patients: poor sleep quality 48%, insomnia 36%, sleep under 7 h 59%; higher risk of insomnia and sleep impairment than controls.

3. Meta-analysis17 studies; 32,907 children

   Li Q, Zhong Q, Kong X, et al. (2026). Allergic rhinitis in children in relation to sleep breathing disorders: a meta-analysis. International Journal of Pediatric Otorhinolaryngology. doi.org/10.1016/j.ijporl.2026.112902

   Allergic rhinitis OR 2.24 in habitual snorers, 1.49 in sleep-disordered breathing, 1.23 in sleep apnea.

4. Meta-analysis12 studies; 19,203 participants

   Ferreira NB, Ponte A, Grande AC, et al. (2025). Frequency of obstructive sleep apnea in patients with asthma or allergic rhinitis: a systematic review and meta-analysis. Sleep Medicine. doi.org/10.1016/j.sleep.2025.106705

   Sleep apnea more frequent with allergic rhinitis (OR 2.4; 95% CI 1.1–5.3).

5. Meta-analysis44 studies; 6,086 participants

   Cao Y, Wu S, Zhang L, et al. (2018). Association of allergic rhinitis with obstructive sleep apnea: A meta-analysis. Medicine (Baltimore). doi.org/10.1097/MD.0000000000013783

   Children with sleep-disordered breathing had 2.12 times higher odds of allergic rhinitis.

Noise at night

Night-time traffic noise is one of the best-studied sleep factors: the odds of being highly disturbed roughly double for every 10 dB louder, and lab recordings confirm more awakenings. For storms, strong wind and fireworks there is no dedicated study, so the forecast gives them a small weight.

1. Meta-analysis74 studies

   Basner M, McGuire S (2018). WHO Environmental Noise Guidelines for the European Region: A Systematic Review on Environmental Noise and Effects on Sleep. International Journal of Environmental Research and Public Health. doi.org/10.3390/ijerph15030519

   Self-reported sleep disturbance per 10 dB night noise (when the question named noise): OR 1.94 aircraft, 2.13 road, 3.06 rail; awakenings per 10 dBA indoor peak: OR 1.35–1.36.

2. Meta-analysis68 observational studies, 152 effect sizes

   Li Z (2026). Environmental Noise Exposure and the Risk of Sleep Disturbance: A Systematic Review and Meta-Analysis. Noise & Health. doi.org/10.4103/nah.nah_222_25

   Correlation with sleep disturbance: aircraft r = 0.26, railway r = 0.21, road r = 0.15 (high certainty; very high heterogeneity).

3. Meta-analysis36 studies, about 173,000 responses

   Smith MG, Cordoza M, Basner M (2022). Environmental Noise and Effects on Sleep: An Update to the WHO Systematic Review and Meta-Analysis. Environmental Health Perspectives. doi.org/10.1289/EHP10197

   Odds of being highly sleep disturbed per 10 dB night noise: aircraft 2.18, road 2.52, railway 2.97.

4. Meta-analysis15 articles

   Godono A, Ciocan C, Clari M, et al. (2023). Association between exposure to wind turbines and sleep disorders: A systematic review and meta-analysis. International Journal of Hygiene and Environmental Health. doi.org/10.1016/j.ijheh.2023.114273

   Sleep disorders in 34% of people living near wind turbines, falling with distance; evidence quality poor.

5. Meta-analysis9 studies reviewed, 5 meta-analysed

   Liebich T, Lack L, Hansen K, et al. (2021). A systematic review and meta-analysis of wind turbine noise effects on sleep using validated objective and subjective sleep assessments. Journal of Sleep Research. doi.org/10.1111/jsr.13228

   No significant effect on objectively measured sleep (e.g. sleep efficiency g = −0.25, not significant).

Humidity

There is no pooled evidence on humidity. Large datasets hint that very dry and very humid air both go with shorter or more broken sleep, and humid air makes heat worse because sweat cools less, so the forecast only counts muggy air on warm nights, with a small weight.

No meta-analysis found.

1. Large study, not a meta-analysis47,628 adults, 68 countries

   Minor K, Bjerre-Nielsen A, Jonasdottir SS, et al. (2022). Rising temperatures erode human sleep globally. One Earth. doi.org/10.1016/j.oneear.2022.04.008

   Humidity results are not stated in the abstract; a later review describes both low and high humidity as reducing sleep duration in this dataset.

2. Large study, not a meta-analysis8,611 sleep-clinic patients (mostly with sleep apnea)

   Tung NT, Lee YL, Liu WT, et al. (2025). Impact of PM2.5, relative humidity, and temperature on sleep quality: a cross-sectional study in Taipei. Annals of Medicine. doi.org/10.1080/07853890.2024.2448733

   Higher relative humidity was associated with changes in non-REM sleep stages and more arousals in all seasons.

Full moon

There is no meta-analysis on the moon and sleep. Some small lab studies found slightly lighter or shorter sleep around full moon, but the largest datasets find no effect or about 5 minutes, and researchers have documented publication bias. The forecast shows the moon but gives it almost no weight.

No meta-analysis found.

1. Large study, not a meta-analysis5,812 children, 12 countries, 33,710 accelerometer days

   Chaput JP, Weippert M, LeBlanc AG, et al. (2016). Are Children Like Werewolves? Full Moon and Its Association with Sleep and Activity Behaviors in an International Sample of Children. Frontiers in Pediatrics. doi.org/10.3389/fped.2016.00024

   Sleep was about 5 min shorter at full moon than at new moon; no other differences.

2. Large study, not a meta-analysis2,125 adults with home polysomnography

   Haba-Rubio J, Marques-Vidal P, Tobback N, et al. (2015). Bad sleep? Don't blame the moon! A population-based study. Sleep Medicine. doi.org/10.1016/j.sleep.2015.08.002

   No significant differences between lunar phases in subjective or objective sleep.

3. Large study, not a meta-analysisPooled reanalysis of sleep-lab datasets (no abstract)

   Cordi M, Ackermann S, Bes FW, et al. (2014). Lunar cycle effects on sleep and the file drawer problem. Current Biology. doi.org/10.1016/j.cub.2014.05.017

   No statistically relevant link between sleep and lunar phase; publication bias may explain earlier positive findings.

4. Large study, not a meta-analysisSmall laboratory sample (not stated in abstract)

   Cajochen C, Altanay-Ekici S, Münch M, et al. (2013). Evidence that the lunar cycle influences human sleep. Current Biology. doi.org/10.1016/j.cub.2013.06.029

   Around full moon, deep-sleep EEG activity was 30% lower and total sleep 20 min shorter. The most-cited positive study.

Collective stress

During the COVID-19 pandemic, about a fifth to two-fifths of the general population had sleep problems in meta-analyses of up to half a million people, and lockdowns made it worse. Earthquakes and war show clear, mostly temporary jumps in insomnia in large single studies. We have not found a reliable daily news-stress signal yet, so this is shown here but not used in the forecast.

1. Meta-analysis250 studies; 493,475 participants; 49 countries

   Jahrami HA, Alhaj OA, Humood AM, et al. (2022). Sleep disturbances during the COVID-19 pandemic: A systematic review, meta-analysis, and meta-regression. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2022.101591

   Global prevalence of sleep disturbances 40.49%; general population 36.73%; higher during lockdown (42.49% vs 37.97%).

2. Meta-analysis177 papers; 345,270 participants; 39 countries

   Alimoradi Z, Broström A, Tsang HWH, et al. (2021). Sleep problems during COVID-19 pandemic and its' association to psychological distress: A systematic review and meta-analysis. EClinicalMedicine. doi.org/10.1016/j.eclinm.2021.100916

   Sleep problems in 18% of the general population, 31% of healthcare workers and 57% of COVID-19 patients.

3. Meta-analysis154 studies

   Ceolin C, Limongi F, Siviero P, et al. (2024). Changes in Sleep Duration and Sleep Timing in the General Population from before to during the First COVID-19 Lockdown: A Systematic Review and Meta-Analysis. International Journal of Environmental Research and Public Health. doi.org/10.3390/ijerph21050583

   Sleep duration rose slightly during lockdown (SMD 0.25); sleep timing was moderately delayed and napping increased.

4. Meta-analysis139 studies

   Scarpelli S, Zagaria A, Ratti PL, et al. (2022). Subjective sleep alterations in healthy subjects worldwide during COVID-19 pandemic: A systematic review, meta-analysis and meta-regression. Sleep Medicine. doi.org/10.1016/j.sleep.2022.07.012

   Pooled PSQI 6.73 (in the poor-sleep range); pooled insomnia severity 8.44 (subthreshold).

5. Meta-analysis66 studies; 42,956 participants

   Carpinelli LP, Gauer LE, Soares VHD, et al. (2026). Insomnia and poor sleep quality in refugee and asylum-seeking populations: A systematic review and meta-analysis. PLoS ONE. doi.org/10.1371/journal.pone.0352964

   Sleep problems in 43.2% of adults and 36.4% of children; pooled insomnia severity 13.76.

6. Large study, not a meta-analysisNationwide random samples of about 1,250 people per wave

   Itoh Y, Takeshima M, Kaneita Y, et al. (2022). Associations Between the 2011 Great East Japan Earthquake and Tsunami and the Sleep and Mental Health of Japanese People: A 3-Wave Repeated Survey. Nature and Science of Sleep. doi.org/10.2147/nss.s338095

   Insomnia rose from 11.7% to 21.2% four months after the disaster and returned to 10.6% at 18 months.

7. Large study, not a meta-analysisNational survey N = 6,474 plus three further samples

   Zak U, Choshen-Hillel S, Hochner H, et al. (2025). Tired of war: Changes in the sleep of the Israeli civilian population in the wake of the Israel-Hamas war. International Journal of Clinical and Health Psychology. doi.org/10.1016/j.ijchp.2025.100596

   Short sleep (under 6 h) up 19–22%, clinical insomnia up 16–19%; most effects persisted at 6 months.

Daylight and season

People sleep slightly longer in the darker months and less when days are long, and more evening light (for example at the western edge of a time zone) goes with shorter sleep. The effects are small, roughly 10–20 minutes, and the few meta-analyses disagree, so this is not yet used in the forecast.

1. Meta-analysis18 studies, 986 participants

   Shao Y, Li Y, Wang N, et al. (2024). Effect of daily light exposure on sleep in polar regions: A meta-analysis. Journal of Sleep Research. doi.org/10.1111/jsr.14144

   Intense summer light reduced sleep time and efficiency; moderate spring/autumn light delayed sleep.

2. Meta-analysis17 studies (11 on season), 1,951 adults

   Ferguson T, Curtis R, Fraysse F, et al. (2021). Annual, seasonal, cultural and vacation patterns in sleep, sedentary behaviour and physical activity: a systematic review and meta-analysis. BMC Public Health. doi.org/10.1186/s12889-021-11298-3

   Sleep was highest in autumn (+12 min above the yearly mean), but not statistically significant.

3. Meta-analysisNot stated in abstract

   Weaver RG, Hensing C, Armstrong B, Adams EL, Beets M (2022). Seasonal Shifts in Children's Sedentary Behaviors, Physical Activity, and Sleep: A Systematic Review and Meta-Analysis. Pediatric Clinics of North America. doi.org/10.1016/j.pcl.2022.04.005

   The authors note a paucity of data on seasonal variation in sleep.

4. Meta-analysis53 studies, 1,154 participants

   van Maanen A, Meijer AM, van der Heijden KB, Oort FJ (2016). The effects of light therapy on sleep problems: A systematic review and meta-analysis. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2015.08.009

   Light therapy improved sleep problems overall (g = 0.39) and insomnia (g = 0.47). Indirect evidence: light as treatment.

5. Large study, not a meta-analysis416,731 adults

   DelRosso LM, Vodapally M (2026). Seasonal and geographic variation in sleep duration among U.S. adults: Evidence from the 2022 BRFSS. Chronobiology International. doi.org/10.1080/07420528.2025.2611866

   Monthly variation was modest (7.82 h in April to 8.13 h in January); latitude and time-zone differences were small.

6. Large study, not a meta-analysisUS time zone border comparison

   Giuntella O, Mazzonna F (2019). Sunset time and the economic effects of social jetlag: evidence from US time zone borders. Journal of Health Economics. doi.org/10.1016/j.jhealeco.2019.03.007

   One extra hour of evening natural light reduced sleep by 19 min on average.

Weather fronts and air pressure

Many people say fronts affect their sleep, but no meta-analysis has looked at pressure and sleep, and the few direct studies are small and contradict each other. Pressure is linked a little to migraine, but not consistently to pain. The forecast shows big pressure swings so your votes can test the idea, but they do not affect the score.

1. Meta-analysis31 studies (about migraine, not sleep)

   Li S, Liu Q, Ma M, et al. (2025). Association between weather conditions and migraine: a systematic review and meta-analysis. Journal of Neurology. doi.org/10.1007/s00415-025-13078-0

   Ambient pressure was significantly associated with migraine attacks (OR 1.07, 95% CI 1.01–1.15).

2. Meta-analysis11 studies, 15,315 participants (about pain, not sleep)

   Ferreira ML, Hunter DJ, Fu A, et al. (2024). Come rain or shine: Is weather a risk factor for musculoskeletal pain? A systematic review with meta-analysis of case-crossover studies. Seminars in Arthritis and Rheumatism. doi.org/10.1016/j.semarthrit.2024.152392

   No association between air pressure and rheumatoid arthritis, knee or low back pain.

3. Large study, not a meta-analysis7,523 sleep-lab patients

   Cassol CM, Martinez D, da Silva FABS, et al. (2012). Is sleep apnea a winter disease?: meteorologic and sleep laboratory evidence collected over 1 decade. Chest. doi.org/10.1378/chest.11-0493

   Sleep apnea severity correlated inversely with temperature and directly with atmospheric pressure.

4. Large study, not a meta-analysis537 sleep-lab patients

   Doherty MJ, Youn CE, Haltiner AM, et al. (2010). Do weather-related ambient atmospheric-pressure changes influence sleep disordered breathing?. Journal of Clinical Sleep Medicine. doi.org/10.5664/jcsm.27764

   Obstructive apnea rose with lower pressure, the opposite direction to the study above.

Space weather (geomagnetic storms)

We found no study that measured human sleep against geomagnetic activity, only small, older studies reporting lower melatonin (a sleep hormone) during geomagnetic disturbances. The forecast shows the Kp index for interest, but it does not affect the score.

No meta-analysis found.

1. Large study, not a meta-analysis153 utility workers (melatonin measured, not sleep)

   Burch JB, Reif JS, Yost MG (2008). Geomagnetic activity and human melatonin metabolite excretion. Neuroscience Letters. doi.org/10.1016/j.neulet.2008.04.031

   Higher geomagnetic activity was associated with lower nocturnal melatonin-metabolite levels.

2. Large study, not a meta-analysis132 utility workers (melatonin measured, not sleep)

   Burch JB, Reif JS, Yost MG (1999). Geomagnetic disturbances are associated with reduced nocturnal excretion of a melatonin metabolite in humans. Neuroscience Letters. doi.org/10.1016/s0304-3940(99)00308-0

   Overnight melatonin-metabolite excretion was lower on geomagnetically disturbed days.

3. Large study, not a meta-analysis25 healthy subjects (melatonin measured, not sleep)

   Weydahl A, Sothern RB, Cornélissen G, et al. (2001). Geomagnetic activity influences the melatonin secretion at latitude 70 degrees N. Biomedicine & Pharmacotherapy. doi.org/10.1016/s0753-3322(01)90006-x

   Large geomagnetic changes significantly decreased salivary melatonin.