Thursday, October 29, 2009

Whether the weather: Climate schmimate

A few months ago, one of my kids (let's call him "Thing no. 3") decided to go all croup-y and respiratory distressed, thus necessitating a post-midnight trip to the local party-hard-capital-of-the-Universe, the Emergency Department.
Naturally, once the adrenalin and cortisol levels brought on by an exciting trip to the hospital had kicked in, and we were in the nice, warm, climate controlled hospital environment, Thing 3 immediately category 5-ed himself, which was both a relief and slightly embarassing. For those of you who haven't had to do any emergency triage lately, category 5 is the "running around yelling "wheeee"" category, as opposed to the "arriving dead - crap, we'd better do something about it right now" category 1 at the opposite end of the scale.
While Thing 3 ran around the paeds waiting room entertaining the other, distinctly un-sick looking kids, I had ample time to catch up on my television infommercials and think thoughts of health and climate.

Viral croup has long been recognised as cropping up in epidemics during the winter months, and often is most acute at night-time when children's bedrooms are colder. This is such accepted epidemiology that most guidelines and textbooks don't even bother referencing these factoids (but if you're really keen you can lit search it yourself if you don't believe me - or alternatively, Listen To Your Mother. She knows.) However, I would probably stop short of saying that Thing 3 got struck by the climate. He had a higher likelihood of getting croup because of the climate, but was probably more likely a victim of the weather. If he had the same viral infection on a warmer evening, he might not have gone all dramatically Sarah Bernhardt on me in the middle of the night.

There seems to be a bit of mis-use or mis-appropriation of the word climate in health care. Climate is a valid determinant of health but is not often a causative factor of mortality. Weather is much more likely to off you, but when can you blame weather and when can you blame climate? Climate is an average across a period of time or across a geographic span across time. Weather is what is happening right now in a given spot. So if you get caught out in a blizzard, I would probably say you got killed by the weather. Sure, you probably lived in a cold climate to have blizzards (or were spectactularly unlucky and should be written up in Fortean Times), but I would probably say the weather got you. If you got cataracts or skin cancer and lived in Australia, I would say that climate could be a part of what caused it (that and probably being caucasian), but skin cancer and cataracts are generally cumulative processes that occur over time, just like "climate". You couldn't definitively pick the one sunny day that did it, you can just extrapolate a bit from statistics.

Given that labelling "climate" as an actual directly causative factor of mortality (when you really mean "weather") is a bit on the fuzzy side, one would think that attributing deaths to "climate change" is plunging logic deep into hazy land. Pardon me my cynicism, but one suspects that the overall fuzziness of the association might be the point of the exercise. It often doesn't occur to anyone to question it, " said what, now? Exactly how do you figure this?"

Contrary to much popular belief, its actually pretty bad for your health to live in a colder climate. Sure, you get wa-ay more exciting parasites in the tropics, but much of the warm latitudes mortality can be attributable to the fact that that is where many of the world's poor people live. (Should I include Florida in that? I'm not sure...)

For instance, if you were worried about keeling over from heart disease, and hey, who isn't - ischaemic heart disease and cardiovascular disease are the top two causes of mortality in Australia, you are more likely to do so in winter. This could be for a variety of reasons, and the fact that spikes in overall mortality in developed nations in winter correlate with influenza rates is either part of the problem or at least doesn't help much.

Last year, the American Heart Association published a paper called "The "Sunshine Deficit" and Cardiovascular Disease", which neatly summarised some of the more recent research and thinking in this area. They noted that:

Vitamin D deficiency links to cardiovascular disease can be found in a number of studies demonstrating a 30% to 50% higher cardiovascular morbidity and mortality associated with reduced sun exposure caused by changes in season or latitude. Conversely, the lowest rates of heart disease are found in the sun-drenched Mediterranean coast and in southern versus northern European countries. Cardiac death has been reported to be the highest during winter months.

It would seem that these days you can blame Vitamin D deficiency for almost everything, and much of this began as a process of inquiry into why morbidity and mortality could be epidemiological correlated with latitude, season and weather. There is lots of fascinating biochemistry (if you're into that sort of thing) about the role of Vitamin D being discovered as a result, and we may get bored with the Vitamin D hypothesis in the future or figure out it's a bit more complicated than we thought. Be this as it may, the statistical relationship between morbidity, mortality and temperate climes still remains, regardless of the present explanation de jour.

So back up off of blaming everything on global "warming", or worse yet, climate "change", unless you can tell me explicitly in 150 words or less why you should be allowed to use the word "climate" as a causative factor for mortality in the first case. Then we can argue the "change" bit later...

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