Seasonal variation of relapses in multiple sclerosis suggests that season-dependent factors, such as ambient air pollution, may trigger them. However, only few studies have considered possible role of air pollutants as relapse's risk factor.
Researchers have investigated the effect of particulate matter of aerodynamic diameter smaller than 10microm ( PM10 ) on multiple sclerosis relapses.
In total, 536 patients with relapsing multiple sclerosis from Strasbourg city ( France ) were included, accounting for 2052 relapses over 2000-2009 period.
A case-crossover design was used with cases defined as the days of relapse and controls being selected in the same patient at plus and minus 35 days. Different lags from 0 to 30 days were considered.
The natural logarithm of the average PM10 concentration lagged from 1 to 3 days before relapse onset was significantly associated with relapse risk ( odds ratio, OR =1.40 [ 95% confidence interval 1.08-1.81 ] ) in cold season.
Consistent results were observed when considering PM10 as a binary variable, even if not significant.
In conclusion, with an appropriate study design and robust ascertainment of neurological events and exposure, the present study highlights the effect of PM10 on the risk of relapse in patients with multiple sclerosis, probably through oxidative stress mechanisms. ( Xagena )
Roux J et al, Environ Res 2017; Epub ahead of print