The Myth of the Common Cold

I have a slight cold today; meanwhile poor Becky who should basking in the Balearic’s has a horrendous one. Of course her holiday is marred by constant rain anyway — but even so, sounds like she is pretty miserable. All around me people are catching dreadful colds, as the t -shirts of summer give way to the pullovers of autumnal England. The weather turns cold, and in the word of Bowie “you’ll sneeze and catch a  cold; cos you left your coat behind”, sentiments echoed by folk wisdom for centuries. Dress up warm in the cold, or you’ll catch cold. Yet intelligent sceptics know this is all rot – the common cold is caused by a virus, and nothing to do with weather. It’s all been debunked for years. But has it really? Or is this actually a myth?

Actually, I think it isa myth. I did a quick  search on evidence based medicine and statistical research, and found this

http://linkinghub.elsevier.com/retrieve/pii/S0954611108003429

So colds are associated with colder weather.

We need to think it through though – correlation is not necessarily evidence of causation (though it very often is!)

So–

1. The cold virus is likely to be dormant or less active in winter at sub-zero temperatures?
2. Yet people still get colds in winter, and cold weather does appear at the anecdotal level to be related to the common cold.

So why?

Well, what if we are constantly exposed to cold viruses in the environment? Then we might expect that given equal exposure, we would all be ill equally across the seasonal weather and temperature changes throughout the year.

Except: our immune systems might vary? We might be equally exposed, but more susceptible if the immune system was depressed. So could cold weather somehow depress our immune systems?

Cold virus from http://viraldiseases.wikispaces.com/

So does immune resistance vary with body temperature? Makes no sense, as our internal body temperature remains relatively static, and homeostasis is designed to allow an organism to adapt to prevailing conditions? However, what if variation in exposure to external temperature conditions leads to physiological shifts in the immune system? If so, going from a war environment to a very cold one or vice versa MIGHT actually depress our immune system resistance, even for only a few minutes — allowing a window for the cold virus to take effect in the host.  So it’s not the cold that causes us to catch colds, but sudden changes in temperature.

Logically then in an English winter going from a hot room to a freezing cold night could lead to an increase in cold infections by temporary immune system suppression, and as the virus despite the cold conditions that are less than optimum for replication is still present in the environment, colds increase. It would be exposure to rapidly varying temperatures rather than the cold itself which would lead to the illness.

An obvious objection: then we would expect to see more of all viruses in times when people pass from very warm environments so to very cold ones — but we may well do so, it is just that the highly infectious and environmentally prevalent common cold would appear more than say measles, allowing for the folk belief to arise from actual observations.

Of course this is probably rot — I know nothing worth knowing bout the subject, just speculating.  But if there was some actual enzyme or other change associated with the nose and eyes that might cause brief immune suppression during rapid temperature change as the body adjusts, that might well be the way that the common cold normally enters the body, and that might be worth investigating?

Anyway hope Becky is recovering and enjoying her holiday, and best wishes to everyone else cursed with a cold this week!

cj x

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