Warmer outdoor temperature is associated with worse cognitive status in multiple sclerosis
- Source: Neurology, Mar 27, 2012
By Victoria M Leavitt, et al.
[Note: Dr. Charles Shepherd, Hon Medical Adviser to the ME Association, joins Dr. David Bell and other ME/CFS & fibromyalgia specialists in noting that these illnesses share many symptoms with multiple sclerosis - and this tendency to increased cognitive difficulties in warmer weather is one of them. Regarding ME/CFS and FM, Dr. Sarah Myhill’s theory is that poor mitochondrial energy generation requires the body to conserve blood/oxygen supply to the organs, including first the skin, causing heat intolerance, and eventually other organs including cardiovascular system and brain, causing orthostatic and cognitive symptoms.]
Objective: Patients with multiple sclerosis (MS) have more clinical exacerbations and T2 lesion activity during warmer weather. [T2 lesions are the bright spots that appear on MRI images of the MS patient’s brain. Lesions are seen in MRI brain scans of ME/CFS patients also.]
The current study is the first to investigate:
• Whether outdoor temperature is related to cognitive status across patients with MS (cross-sectional analysis),
• And whether cognitive status fluctuates with changes in outdoor temperature within patients with MS (longitudinal analysis).
Methods: For the cross-sectional analysis, 40 patients with MS and 40 healthy control (HC) subjects were recruited throughout the calendar year. Cognitive status (processing speed, memory) and outdoor temperature were recorded for the day of testing.
We calculated partial correlations between cognitive status and temperature for patients with MS and HCs, controlling for demographic and disease variables.
For the longitudinal analysis, cognitive status and outdoor temperature were recorded at baseline and 6-month follow-up in a separate sample of 45 patients with MS. We calculated the partial correlation between temperature and cognitive status at follow-up, controlling for baseline temperature and cognitive status (i.e., whether temperature changes are related to cognitive changes within patients with MS).
Results: Cross-sectionally, warmer temperature was related to worse cognitive status in patients with MS (rp = ?0.45, p = 0.006), not in HCs (rp = 0.00, p = 0.984). Longitudinally, increased outdoor temperature from baseline to follow-up was related to a decline in cognitive status within patients with MS (rp = ?0.39, p = 0.010).
Conclusions: Cognitive status in patients with MS is worse on warmer days, consistent with a previously established link between heat and lesion activity.
Our findings have implications for clinical trial planning, treatment, and lifestyle decisions. We discuss cognitive status as a potential marker of quiescent exacerbations.
Source: Neurology, Mar 27, 2012; 78-964-968. Leavitt VM, Sumowski JF, Chiaravalloti N, DeLuca J. Kessler Foundation Research Center, West Orange, New Jersey; Departments of Physical Medicine & Rehabilitation and Neurology & Neurosciences, UMDNJ–New Jersey Medical School, Newark, New Jersey, USA. [Email: firstname.lastname@example.org]