Family Practice Advance Access originally published online on November 14, 2005
Family Practice 2005 22(6):608-613; doi:10.1093/fampra/cmi072
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Acute cooling of the feet and the onset of common cold symptoms
Common Cold Centre, Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3US, UK
Correspondence to Professor Ronald Eccles, Common Cold Centre, Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3US, UK; Email: eccles{at}cardiff.ac.uk
Received 8 November 2004; Accepted 31 May 2005.
Johnson C and Eccles R. Acute cooling of the feet and the onset of common cold symptoms. Family Practice 2005; 22: 608–613.
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Abstract |
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Background. 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.
Objective. This study will test the hypothesis that acute cooling of the feet causes the onset of common cold symptoms.
Methods. 180 healthy subjects were randomized to receive either a foot chill or control procedure. All subjects were asked to score common cold symptoms, before and immediately after the procedures, and twice a day for 4/5 days.
Results. 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). There was no evidence that chilling caused any acute change in symptom scores (P = 0.62). Mean total symptom score for days 1–4 following chilling was 5.16 (±5.63 s.d. n = 87) compared to a score of 2.89 (±3.39 s.d. n = 88) in the control group (P = 0.013). The subjects who reported that they developed a cold (n = 18) reported that they suffered from significantly more colds each year (P = 0.007) compared to those subjects who did not develop a cold (n = 162).
Conclusion. 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.
Keywords. Cold exposure, common cold, infection, nose.
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Introduction |
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The common cold is a mild self-limiting illness usually confined to the upper respiratory tract.1 The disease is self-diagnosed from a range of symptoms such as nasal stuffiness, sneezing, throat irritation and mild fever.2 There is a common folklore that associates the development of symptoms of common cold with exposure to a cold environment, and that the onset of a cold is a direct result of wet clothes, feet and hair.3 Throughout the clinical literature of the last three hundred years there have been many reports that acute cooling of the body surface causes the onset of symptoms of common cold, and historically it has been generally accepted that acute exposure to cold is a direct cause of these symptoms.4,5
However, studies involving inoculation of cold viruses into the nose and periods of cold exposure have failed to demonstrate any effect of cold exposure on susceptibility to infection with common cold viruses.6–8 Although modern textbooks of virology dismiss any cause-and-effect relationship between cold exposure and common cold as erroneous folklore,9 the belief is so widespread and longstanding it is difficult to completely dismiss this idea as having no validity.
In 1919 Mudd and Grant studied the reactions of the nasal mucosa in response to chilling the body surface and showed that cooling the body surface causes a reflex vasoconstriction of blood vessels in the nose and a decrease in temperature of the mucous membrane.10 They speculated that this reflex vasoconstriction of the airway epithelium could decrease resistance to infection and allow bacterial infection of the tonsils.10 Some years later Sir Christopher Andrewes suggested that exposure to a cold environment may trigger the development of a cold but only in people who are carrying the latent cold virus.6 Eccles developed these early observations by proposing a hypothesis that acute cooling of the body surface causes a reflex vasoconstriction in the nose and upper airways, and this vasoconstrictor response may inhibit respiratory defence and cause the onset of common cold symptoms by converting an asymptomatic viral infection (sub-clinical infection) into a symptomatic viral infection (clinical infection).11 The novel idea in this hypothesis was that when common cold viruses are circulating in the community a proportion of those infected will have sub-clinical infections, and that when any of this sub-group are exposed to chilling of the body surface this could aid conversion of a sub-clinical infection to a clinical infection. This study was aimed at testing this hypothesis, by studying the onset of common cold symptoms after acute chilling of healthy asymptomatic subjects, during the winter, when common cold viruses are circulating in the community.
The aims of the study were to determine if acute chilling caused: acute onset of common cold symptoms within minutes of chilling; delayed onset of common cold symptoms over a 4/5 days period after chilling; the perception that the subjects were suffering from a common cold over a 4/5 days period after chilling. The study also aimed to investigate any relationship between the history of colds incidence in the previous year and the onset of common cold symptoms.
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Methods |
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Subject population
180 healthy subjects were recruited from the student population of Cardiff University. All subjects attended the Common Cold Centre, Cardiff. All procedures were carried out under standard conditions at a room temperature of eighteen to twenty-five degrees centigrade. Subjects were not permitted to smoke or consume food or drink during the study period. All subjects were given a patient information leaflet to read and were asked to sign the consent form. After signing the consent form the subjects completed a questionnaire about their medical history and their suitability for inclusion into the study was checked. Subjects were deemed suitable for inclusion in the study if the subject was over eighteen years old and healthy as determined by medical history. Subjects were not enrolled in the study if the subject had suffered with acute upper respiratory tract infection in the previous two weeks, or if the subject had a history of seasonal or perennial rhinitis.
Experimental procedures
Once enrolled into the study subjects were randomized to receive chilling or control procedures. A computer generated randomization list was used to assign subjects to either the chill or control procedure with subjects stratified according to the number of common colds reported by the subject in the previous year. Subjects with 0–3 colds in the previous year were allocated to the next available procedure at the start of the randomisation list and subjects with 4 or more colds were assigned to the next available procedure at the end of the list. Ninety subjects were allocated to receive the chill procedure and ninety subjects to receive the control procedure. If allocated to the chilling procedure, the subject was asked to remove their shoes and socks and place their feet in a bowl containing 9–10 litres of water at a temperature of 10°C for twenty minutes. The temperature of the cold bath was monitored (Pen shape digital multi-stem thermometer, Scientific Laboratory Supplies Ltd, Wilford Industrial Estate, Nottingham, UK) and ice was added if necessary to maintain the water temperature at 10°C. If allocated to the control procedure the subject was asked to keep their shoes and socks on and place their feet in an empty bowl for twenty minutes. Warm water was not used as a control as it was believed that this stimulus could have influenced nasal blood flow.
Symptom scores
All subjects were asked if they were suffering with a cold and to score symptoms of runny nose, blocked nose, sore throat, sneezing and cough on a scale of 0–3 with 0 = not present, 1 = mild, 2 = moderate, 3 = severe before and immediately after the procedure. The same common cold question and symptom scores were also used in a daily diary. The method of symptom scores has been widely used in previous studies on common cold.12,13 All subjects were provided with a diary, in which they were instructed to score symptoms and at the same time to indicate if they believed they were suffering from a common cold (day 1 PM, days 2 and 3 AM/PM, day 4 AM, and on visit two which occurred on day 4 or 5).
Nasal airflow was measured as a Nasal Partitioning Ratio (NPR) as described by Cuddihy and Eccles14 before the procedures and on day 4/5 using the GM NV1 spirometer (GM Instruments Ltd, Unit 6 Ashgrove, Ashgrove Rd, Kilwinning, Scotland, UK). NPR was believed to be useful as an objective measure to confirm the presence of acute rhinitis. However the measurements of NPR proved to be too variable to provide any meaningful data and these results are not presented in the present paper.
Previous history of colds
As part of the clinical history subjects were asked how many colds they had suffered from in the previous year.
Statistics
This was a pilot study and it was therefore not possible to perform a power calculation, but the ratio of sub-clinical to clinical infection was considered in order to determine the sample size required for the study. It was predicted that 29 subjects in the chilled group would develop colds and 9 subjects in the control group giving a maximum difference between the groups of 20 and a minimum of 10 depending on the distribution of spontaneous colds. Statistical comparisons were made between the two experimental groups of subjects; chilled and control. The hypotheses were tested at a 0.05 level of significance. The Mann-Whitney test was used to test for differences in symptom scores and history of colds incidence. The immediate effects of chilling were studied by comparing the differences from baseline to immediately after the test procedures in total symptom scores, between chilled and control groups. The delayed effects of chilling were studied by comparing the differences in total symptom scores between chilled and control groups over the 4/5 days period after the test procedures. Mean total symptom scores have been used to describe the symptom score data in the text as this descriptive shows a change in the symptom score, whereas the median does not due to the large number of zero scores. The total symptom scores (days 1 + 2 + 3 + 4/5, maximum score 120) were also analysed as dichotomous data using the Chi-squared test, with total scores of 0–8 indicating absence of a cold and 9–120 indicating presence of a cold. The Chi-squared test was used to test for differences in the number of colds reported by the two test groups in their diaries. A subject was deemed to have experienced a cold if they reported they were suffering from a cold on any occasion after the test procedures on days 1 + 2 + 3 + 4/5.
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Results |
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Subject demographics
180 subjects were enrolled in the study between October 2003 and March 2004, 90 were randomized to the chill procedure, and 90 to the control procedure. The flow diagram in Figure 1 shows the flow of participants through each stage of the study. The demographics of the two test groups are provided in Table 1 that demonstrates that the test groups were balanced and there was no significant difference in any of the baseline characteristics.
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Acute effects of chilling
The test procedures did not cause any significant changes in symptom scores, and all the mean scores were close to zero indicating few or no symptoms were present before or immediately after the procedures as illustrated in Table 2. The small difference in symptom scores between the two groups prior to the procedures was not significant (P = 0.245). The difference in total symptom score pre and post chill procedure was not significantly higher than the difference in total symptom score pre and post control procedure (P = 0.62).
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Delayed effects of chilling
Table 3 shows the mean daily scores and total score for days 1 to 4/5 following each procedure. Total symptom scores for days 1–4/5 following the chill procedure (5.16 ± 5.63 s.d.) were significantly higher than the total symptom scores for days 1–4/5 following the control procedure (2.89 ± 3.39 s.d.) (P = 0.013). When the total symptom scores for the 4/5 days were analysed as dichotomous data, 26/90 (28.8%) of the chilled subjects and 8/90 (8.8%) of the control subjects were deemed to be suffering from a cold (total symptom score 9–120), and this difference was significant (P = 0.001).
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The total number of subjects that reported they were suffering from a common cold in their diaries during the 4/5 days following the chill or control procedures is shown in Figure 2 and this illustrates that significantly more subjects believed they were suffering from a cold in the chilled group (13/90, 14.4%) compared to the control group (5/90, 5.6%, P = 0.047). There was no sex difference in the development of colds with 9.3% of males and 10.3% of females developing colds (P = 0.828, Chi-squared). Of those in the chilled group that developed colds 4/13 were male (31%) and 9/13 female (69%), but this sex difference merely reflects the proportions of males (28%) and females (72%) exposed to the chill procedure and is not significant (P = 0.749, Fisher Exact).
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Colds history in previous year
There was no difference in colds incidence between the two test groups at baseline as illustrated in Table 1. However, when looking at both test groups combined, those subjects who believed there were suffering from a cold had a history of more colds each year (median 2.00, range 1–10) compared to those who did not develop a cold (median 3.00, range 2–8, P = 0.007).
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Discussion |
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Acute effects of chilling
The present study provides no evidence for an acute effect of chilling on the development of common cold symptoms. Symptom scores were close to zero in both the control and chilled groups.
Delayed effects of chilling
A delayed effect of chilling on the incidence of colds and symptoms was observed in the 4/5 days following the chill procedure. Significantly more chilled subjects than control subjects reported they were suffering from colds in the 4/5 days following the test procedures. The difference in the incidence of colds between the two test groups was also supported by a significant difference in total symptom scores over the 4/5 days following the test procedures. Analysis of the symptom scores as dichotomous data also demonstrated a significantly greater symptom score (more colds) in the chilled group. The increased incidence of reports of colds and higher symptom scores in the chilled subjects compared to the control subjects may be due to several factors.
Belief in the folklore that acute chilling of the body surface, in some way precipitates a common cold could have caused some bias in the reporting of colds and symptoms. The subjects were not questioned about their beliefs but the idea was introduced and then dismissed in the informed consent information in the following way:
"This study is designed to investigate the effects of acute chilling on the development of common cold symptoms. It is a popular belief that the development of an upper respiratory tract infection such as the common cold is a result of a chill. However, previous studies have failed to demonstrate that exposure to a cold environment increases the incidence of the common cold.... Common cold symptoms are very common during the winter period and it is expected that some subjects will develop symptoms because they have been previously exposed to infected persons. Therefore the development of any common cold symptoms may be unrelated to any experimental procedures in this study".If the common cold symptoms reported after chilling were solely a result of subject bias caused by belief in the effects of chilling then one would have expected an acute effect of chilling on the scoring of common cold symptoms rather than a delayed effect.
The differences between the chilled and control groups could have occurred as a chance finding, as it was expected that some subjects would develop cold symptoms due to natural exposure to common cold viruses. The probability value for the different reporting of colds was just below P = 0.05 (P = 0.047) but the P-value for the difference in total symptom scores was more convincing with P = 0.013, and for the dichotomous analysis was P = 0.001. With two different measures of the incidence of common cold providing significant differences between the two test groups it is unlikely that the results are solely due to chance.
Chilling of the feet in cold water (12°C ± 1°C) has been previously reported to cause an intense vasoconstriction of both the cutaneous and upper airway blood vessels15 and the vasoconstriction of the upper airways has been proposed as a mechanism that reduces respiratory defence against infection.10,11 When common cold viruses are circulating in the community a proportion of subjects will have sub-clinical infections, and chilling of these subjects may cause vasoconstriction in the upper airway epithelium and conversion of a sub-clinical to a clinical infection. In these cases the subject links the causality of the common cold symptoms to the chill and does not realise that they were already infected before they ‘caught’ a cold. Laboratory studies using viral challenge and cold exposure do not provide any evidence that chilling increases susceptibility to the development of common cold symptoms7,8 but these studies do not mimic the natural exposure to common cold viruses and they can be criticised for the small numbers of subjects used to power the studies.
An interesting finding in the present study was that the subjects who reported they developed a cold after the chill or control procedures also reported that they suffered from significantly more colds each year, than the subjects who did not report a cold after the procedures. This finding may indicate that there is a sub population in the general population who are more susceptible to developing common cold symptoms each year and that they may have a ‘common cold constitution’.16
The results of the present study demonstrate that chilling is associated with the onset of common cold symptoms but the study does not provide any objective evidence, such as virology, that the subjects were infected with a common cold virus. Because of the great variety of viruses causing the common cold syndrome it is difficult to identify the causative agent responsible for common cold symptoms in any subject when viruses are circulating in the community. For this reason it was decided to first study the relationship between chilling and symptoms, and then to consider the use of virology in a subsequent study.
In summary the results of the present study support the folklore that exposure to chilling may cause the onset of common cold symptoms, perhaps by some change in respiratory defence caused by reflex vasoconstriction of the blood vessels of the upper airways. Further studies in this area are needed to determine if the development of common cold symptoms following cold exposure are associated with infection.
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Declaration |
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Funding: the study was funded by Cardiff University. The study sponsor had no involvement in the study design, the collection, analysis and interpretation of data, in the writing of the report or in the decision to submit for publication. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.
Ethical approval: the study was approved by the South East Wales Local Research Ethics Committee.
Conflicts of interest: none.
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References |
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