Qualità delle prove 4.63/5
Punteggio di revisione su otto dimensioni rispetto alla griglia di qualità . Ogni dimensione valutata da 1 a 5.
- D1 Ancoraggio alle fonti
- 4/5
- D2 Autorità delle fonti
- 5/5
- D3 Aritmetica
- 5/5
- D4 Incertezza
- 4/5
- D5 Ambito
- 5/5
- D6 Prosa
- 5/5
- D7 Onestà sulla percezione
- 4/5
- D8 Completezza degli avvertimenti
- 5/5
Come varia il rischio
La cifra principale è una media di situazioni molto diverse. Ecco come varia la probabilità in base allo scenario o al contesto:
1 su 1.000.000
No cohort has measured a respiratory-infection rate attributable to this scenario. Without an underlying viral exposure, cold feet on tile do not produce a cold. Point estimate is a structural "effectively zero" placeholder, not a measured rate.
1 su 7,1 · 14%
Matches the Eccles 2005 arm: ~14% self-reported cold symptoms within 4–5 days after a 20-minute cold-foot immersion vs ~6% in controls. This is a symptom-conversion rate in an already-exposed population under a severe chilling protocol, not an infection rate from going sockless at home.
1 su 20 · 5,0%
Very rough. Order of magnitude derived from WHO cold-housing guidance and UK excess-winter-mortality attribution (~21.5% of ~20,000–50,000 annual excess winter deaths → cold homes, concentrated in over-65s). The dominant pathways are cardiovascular and respiratory, not viral infection. Included as the subgroup the folk warning might actually apply to, even though it is almost never the one a grandmother has in mind when telling a child to put on slippers.
1 su 2,0 · 50%
For someone with a cold-triggered vascular or cardiac condition, bare feet on cold tile reliably produces the trigger (Raynaud's episode, anginal chest pain) — but this is the underlying condition expressing itself, not a new illness. Included only to flag that "cold feet cause real symptoms" is true in this subgroup without rescuing the viral- infection folk model.
La lunghezza e la tonalità della barra ordinano questi scenari tra loro, non rispetto ad altri rischi. Le probabilità esatte sono indicate accanto a ciascuno.
La credenza popolare secondo cui camminare per casa riscaldata senza pantofole, calzini o un maglione provochi il raffreddore è meccanicisticamente sbagliata nella forma in cui viene solitamente espressa, e modestamente corretta in una forma molto più ristretta di quanto le persone che la diffondono tendano a intendere. I raffreddori sono causati da virus (il CDC indica il numero a oltre 200 virus respiratori distinti, con i rhinovirus i più comuni), e sono trasmessi da goccioline e contatto, non dalla temperatura. Senza un’esposizione virale sottostante, i piedi nudi sulle piastrelle producono piedi freddi e nient’altro. La parte del modello popolare che resiste al contatto con le prove è più ristretta: Johnson ed Eccles (Cardiff, 2005) hanno dimostrato in uno studio randomizzato su 180 persone che un’immersione dei piedi in acqua fredda per 20 minuti ha aumentato i sintomi del raffreddore auto-riferiti nei successivi 4–5 giorni dal 6% al 14%, e Foxman et al. (PNAS, 2015) hanno mostrato che il rhinovirus si replica meglio e la risposta immunitaria innata dell’interferone è più debole alla temperatura più fresca di 33–35 °C della cavità nasale rispetto ai 37 °C. Questi due risultati insieme supportano un’unica affermazione specifica: il raffreddamento può convertire un portatore virale subclinico in un raffreddore sintomatico. Non supportano l’affermazione che l’esposizione al freddo produca malattie dal nulla.
Ciò che è interessante di questa particolare paura è il divario tra lo scenario che essa nomina e lo scenario in cui il freddo in casa uccide effettivamente le persone. L’avvertimento popolare viene solitamente rivolto a un bambino o un adulto sano in una casa riscaldata (metti le pantofole, non sederti su piastrelle fredde, non camminare con i capelli bagnati), dove l’effetto di modulazione di Eccles è il limite massimo di ciò che le prove consentono e nessuna coorte ha cercato di misurare un tasso di infezione per inverno attribuibile ad esso. Lo scenario in cui il freddo interno è inequivocabilmente letale è quasi l’opposto demografico: residenti anziani fragili in case mantenute al di sotto di 16–18 °C, dove le Linee guida dell’OMS del 2018 su Alloggi e Salute e i dati sulla mortalità invernale in eccesso dell’ONS del Regno Unito identificano qualcosa come il 21.5% di 20,000–50,000 decessi invernali in eccesso annuali come attribuibili all’abitazione fredda, con malattie circolatorie e respiratorie come cause dominanti. Quel danno riguarda la temperatura ambiente della stanza e lo stress vascolare, non il dimenticare i calzini.
Dove l’inquadramento “trascurabile” non si applica: chiunque abbia il fenomeno di Raynaud scatenerà in modo affidabile un episodio a causa delle piastrelle fredde, indipendentemente dall’infezione, e l’angina indotta dal freddo è un evento cardiaco reale per i soggetti suscettibili. I lettori immunocompromessi che portano un virus respiratorio potrebbero essere più vicini al braccio del 14% di Eccles rispetto alla linea di base della popolazione generale, sebbene lo studio non fosse progettato per affermarlo. Il sottogruppo specifico a cui l’avvertimento popolare dovrebbe essere rivolto per corrispondere ai dati di mortalità da freddo in casa (anziani fragili e neonati in abitazioni poco riscaldate, specialmente con malattie cardiorespiratorie esistenti) di solito non è il sottogruppo che riceve effettivamente l’avvertimento. Il consiglio sulle pantofole è per lo più il giusto istinto culturale puntato sull’esposizione sbagliata.
Curiosità correlate
Camminare sotto la pioggia non ti dara il raffreddore. Sedersi su superfici fredde non causera infezioni alla vescica. Essere poco vestiti non ti fara ammalare. I virus causano le infezioni. La temperatura no.
Registro delle fonti
Ogni numero qui sotto è ciò che ciascuna fonte ha riportato, con la citazione testuale su cui ci siamo basati e come siamo arrivati alla nostra cifra. Clicca su qualsiasi link per verificare direttamente.
2/5 fonti verificate in modo indipendente e alla lettera rispetto alla fonte citata
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[1] Family Practice (Oxford Academic), via PubMed — Acute cooling of the feet and the onset of common cold symptoms
Acute cooling of the feet and the onset of common cold symptomsSee all 3 Likelier entries citing this source →
- Statistica
13/90 chilled subjects vs 5/90 controls self-reported cold symptoms in the 4–5 days after a 20-minute cold-foot immersion (P=0.047)- Estratto
“"There is a common folklore that chilling of the body surface causes the development of common cold symptoms, but previous clinical research has failed to demonstrate any effect of cold exposure on susceptibility to infection with common cold viruses. [...] 13/90 subjects who were chilled reported they were suffering from a cold in the 4/5 days after the procedure compared to 5/90 control subjects (P=0.047). [...] Acute chilling of the feet causes the onset of common cold symptoms in around 10% of subjects who are chilled. Further studies are needed to determine the relationship of symptom generation to any respiratory infection." ”
- Dati originali da
- 2005-12-01
- Consultato
- 2026-04-16 · copia archiviata
- Calcolo
- This is the canonical trial behind any "cold feet causes colds" claim. Critical qualifier the authors themselves flag: the study measured self-reported symptoms, not laboratory-confirmed new infections. The plausible mechanism the authors propose is that reflex vasoconstriction in the upper airway on cold- foot exposure reduces mucosal blood flow and temporarily lowers local defences — converting a pre-existing subclinical carriage of rhinovirus or another respiratory virus into a symptomatic cold. That is a modulation effect, not a causation effect. Without an underlying viral exposure, cooling the feet is not expected to produce illness from nothing. 90 subjects per arm gives an absolute difference of 8 percentage points (14% vs 6%); the confidence bound is wide, and no replication of comparable rigour exists at the scale needed to attach a per-winter probability to "no slippers at home."
- Indipendenza
- Independent single-centre RCT at Cardiff (Common Cold Centre); editorially independent of the CDC and WHO sources. The Foxman 2015 mechanistic paper below provides a biological model compatible with Eccles' clinical result but was conducted in a separate lab with different methodology (mouse airway cells, not human subjects).
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[2] Proceedings of the National Academy of Sciences (PNAS), via PubMed — Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells Verificato
Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cellsSee all 2 Likelier entries citing this source →
- Statistica
Rhinovirus replicates more robustly at 33–35 °C (nasal cavity) than at 37 °C (core body), with weaker interferon/antiviral response at the cooler temperature- Estratto
“"Most isolates of human rhinovirus, the common cold virus, replicate more robustly at the cool temperatures found in the nasal cavity (33–35 °C) than at core body temperature (37 °C). [...] These findings demonstrate that in mouse airway cells, rhinovirus replicates preferentially at nasal cavity temperature due, in part, to a less efficient antiviral defense response of infected cells at cool temperature." ”
- Dati originali da
- 2015-01-20
- Consultato
- 2026-04-16 · copia archiviata
- Verifica
- Estratto recuperato in modo indipendente e confermato parola per parola rispetto alla fonte citata durante il nostro audit di attendibilità.
- Calcolo
- Foxman et al. supplies the cleanest known mechanism for any cold-exposure- to-cold-illness signal: rhinovirus itself replicates better in a cooler nose, and the innate interferon response is weaker at 33 °C than at 37 °C. This makes Eccles' symptom-onset result biologically plausible without rescuing the folk model. The study is mouse airway cells in vitro, not an epidemiological measurement, and no study has translated the temperature- dependent replication curve into a per-exposure infection probability for a human wearing socks versus going barefoot. The mechanism is real; the epidemiological effect size at normal indoor conditions is not quantified.
- Indipendenza
- Yale laboratory study with no authorship, funding, or institutional overlap with the Cardiff Eccles group; treat as methodologically independent mechanistic corroboration. Independent of the CDC and WHO sources.
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[3] US Centers for Disease Control and Prevention — About the Common Cold
About the Common ColdSee all 2 Likelier entries citing this source →
- Statistica
More than 200 respiratory viruses cause colds; rhinoviruses are the most frequent cause; primary spread is droplets and contact- Estratto
“"More than 200 respiratory viruses can cause colds. Rhinoviruses are the most frequent cause of colds in the United States. [...] Most respiratory viruses are spread through droplets that an infected person releases when they cough or sneeze. These droplets can enter your body if you breathe them in or touch a contaminated surface and then touch your eyes, nose, or mouth." ”
- Dati originali da
- 2026-02-19
- Consultato
- 2026-04-16 · copia archiviata
- Calcolo
- CDC's current patient-facing page is the plain-language anchor for the "colds are viral, not thermal" frame. The folk model treats cold exposure as causative; CDC treats virus exposure as causative and does not list chilling or being under-dressed indoors as a transmission route at all. The Eccles and Foxman results sit downstream of this: you still need the virus. Without rhinovirus or one of the other ~200 candidates in your airway, cold feet on tile do not produce a cold.
- Indipendenza
- Institutional CDC public-health guidance; editorially independent of the Eccles clinical trial and Foxman mechanistic paper, though it aligns with both.
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[4] World Health Organization (via NCBI Bookshelf) — Low indoor temperatures and insulation — WHO Housing and Health Guidelines Verificato
Low indoor temperatures and insulation — WHO Housing and Health Guidelines- Statistica
WHO recommends minimum indoor temperature of 18 °C to protect general populations; higher minimum for vulnerable groups (older people, children, chronic cardiorespiratory illness)- Estratto
“"For countries with temperate or colder climates, 18 °C has been proposed as a safe and well-balanced indoor temperature to protect the health of general populations during cold seasons. [...] A higher minimum indoor temperature than 18 °C may be necessary for vulnerable groups including older people, children and those with chronic illnesses, particularly cardiorespiratory disease." ”
- Dati originali da
- 2018-11-27
- Consultato
- 2026-04-16 · copia archiviata
- Verifica
- Estratto recuperato in modo indipendente e confermato parola per parola rispetto alla fonte citata durante il nostro audit di attendibilità.
- Calcolo
- WHO's guideline is the authoritative carve-out for the one scenario in which "being under-dressed at home" really does kill people: under-heated housing in cold climates, especially for the elderly and those with cardiorespiratory disease. The exposure here is the ambient indoor temperature (below ~18 °C sustained), not a barefoot afternoon in a heated 21 °C living room. The outcome is cardiovascular and respiratory morbidity and mortality, not the common cold. This is the reason the headline framing ("folk belief overrated") must be paired with an explicit vulnerable-group caveat rather than a blanket dismissal.
- Indipendenza
- WHO expert consensus guideline synthesising the cold-housing evidence base. Editorially independent of the Eccles, Foxman, and CDC sources and addresses a distinct exposure-outcome pair (sustained low ambient temperature → cardiovascular/respiratory death), not symptom onset of the common cold.
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[5] UK Parliamentary Office of Science and Technology — Winter mortality (POSTnote 752)
Winter mortality (POSTnote 752)- Statistica
Excess winter deaths in England and Wales ranged ~20,000–50,000/year 2000–2019; ~21.5% of excess winter deaths attributable to cold homes; most deaths from circulatory or respiratory disease among the elderly- Estratto
“"Between 2000 and 2019, excess winter deaths ranged from 20,000 to 50,000 a year [...] Most excess winter deaths are due to circulatory or respiratory diseases and the majority occur amongst the elderly population. [...] It has been estimated that 10% of excess winter deaths are attributable to fuel poverty and 21.5% to cold homes." ”
- Dati originali da
- 2024-01-01
- Consultato
- 2026-04-16 · copia archiviata
- Calcolo
- This is the population-scale number for the one real cold-in-the-home harm: under-heated housing kills elderly people through cardiovascular and respiratory pathways, not through infection. It does not apply to the folk-belief scenario (healthy adult, barefoot in a warm house) and should not be aggregated with the Eccles symptom-onset figure. Used here only to bound the vulnerable-group subgroup in the regional breakdown and to keep the caveats honest about who the folk warning, repurposed, actually applies to.
- Indipendenza
- UK Parliament research briefing drawing on ONS winter-mortality data and NICE fuel-poverty reviews. Editorially independent of the WHO guideline (though it references the same underlying epidemiology) and independent of the Eccles, Foxman, and CDC sources.