Seasonal fluctuations in disease have been recognised for millennia. Until recent times, these phenomena were ascribed to changes in the weather. It’s easy to understand why.
This time of the year the weather is predictably unpredictable. Summer is mostly hot. Winter is mostly cold. But spring can be either, on successive days or even in the space of a few hours.
This kind of unsettled weather can be vaguely discontenting. At least half of all adults claim to experience changes in their health with the changing weather, including more frequent headaches, joint pain, tiredness, and even catching more colds.
Even though the nose does not actually block, hotter and humid air will make it feel more congested, like when we’re in the shower. But once we step out, the blast of colder less humid air makes the nose suddenly feel more open, creating that freshening sensation in our head. The same thing happens in reverse when we step from air-conditioned cool indoors into the humid heat outside, making our head feel stuffy.
The vast majority of people with arthritis or chronic back pain feel more discomfort on stormy, cold or damp days, which improves as the weather warms and becomes more constant.
Whether these are a direct effect of the weather or an indirect one (related to the profound effects of seasonal weather on mood, behaviour, diet, physical activity, mobility, participation, perception of illness, pain and many other factors) is unknown.
The weather outside can certainly significantly influence how we feel. Not by as much as most people think and not the same way in everyone. But enough to make a difference.
Sunshine is probably a critical element. We have special sensors in our eyes that feed back the intensity of light to our brains to regulate our biological and hormonal rhythms as well as our alertness and mood.
Our skin uses the ultraviolet radiation in sunlight to make vitamin D which also has important vital functions for health and well-being.
Sunny weather also puts us closer to our comfort zone at around 20 degrees celsius when we neither need to sweat to keep cool or move/shiver to keep warm. The hotter we get above this or the lower we go the less comfortable we feel. This plays on our emotions and the health that results from them.
Many cultures describe “an ill wind”, which rapidly changes the temperature and triggers symptoms of poor health. The most famous examples are the Föhn wind in Europe and the Chinook of the Rocky Mountains.
In Australia, pollen and dust carried by spring northerly winds that whip them up, act as an irritant to eyes, noses and lungs, especially, but not only, in those with allergies.
The moist air associated with seasonal thunderstorms can also concentrate and break up pollen and pollution into smaller particles which are more easily inhaled deep into the lungs and trigger asthma attacks. Warm and moist conditions also promote the release of fungal spores which can set off allergies in some people.
The onset of the debilitating autoimmune-disease multiple sclerosis (MS) or episodes of MS relapse are also more common in springtime. Whether this relates to the latent effect of winter infections on immunity or seasonal fluctuations in our body’s natural immune-modifying substances such as vitamin D or melatonin is unknown.
Breast cancer is also more commonly diagnosed in spring and early summer, and this association is more pronounced the further you get from the equator, where seasonal change is most dramatic. A spring upsurge for prostate cancer diagnosis is also seen in men.
But this is probably just due to behaviour. Spring is traditionally the season we try to get things in order, such as spring cleaning.