Temperature changes can have an impact upon some symptoms experienced by people with MS. Cold temperature can impact nerves and muscle activity, leading to pain and mobility challenges including cramping, stiffness and spasticity. This can lead to difficulty walking or use of the hands. It can also worsen the MS hug, which is a gripping feeling around the torso caused by spasticity of small muscles between the ribs. Advise the person to dress in layers, drink a warm beverage but not to turn the heating up too high inside as excessive heat can exacerbate their MS.
Some other things to look out for during the colder months include depression and infections. Depression is more common during the colder months. MS and depression are closely related; while MS can worsen or trigger depression, depression can also make it hard for the person with MS to function. Infections, which may trigger an MS relapse, are also more common during winter months.
Heat can also impact upon people with MS and they can often experience a temporary worsening of their symptoms in hot weather. Common symptoms triggered by heat include fatigue, blurred vision, tremor, weakness and cognitive problems.
Disease activity can also be impacted by the seasons. A growing number of studies have addressed the importance of environmental factors in MS for ongoing activity of established disease, and seasonal variation in relapses has been demonstrated in some studies. Higher rates of relapse activity among individuals with MS have generally been observed in spring and summer months, irrespective of latitude. In a large northern European population-based study spanning a decade, a seasonal pattern in MS events was observed, with a peak in late spring/early summer, and a trough in late summer. This pattern was most apparent in younger patients with relapsing–remitting disease and was associated with monthly hours of sunshine.1 However, this did not account for all variation observed, suggesting that seasonal patterns of MS events are multifactorial. In contrast, a recent study of 13,575 Danish patients with RRMS treated with DMTs observed a significantly lower number of relapses in July.2 These seasonal differences in relapse rates highlight the importance of environmental factors in disease expression. Identification of potentially modifiable factors associated with this variation may offer unique opportunities for alteration of risk of relapse and long-term outcome on a population level.
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