Weather as a trigger of stroke. Daily meteorological factors and incidence of stroke subtypes

Background: The conclusions of previous studies show little agreement concerning the relationship between weather and the incidence of stroke. We analyse the relationship between daily meteorological conditions and daily as well as seasonal stroke incidence.

Methods: 1,286 consecutive strokes assessed during 3 years (2001-2003) from the reference area of Hospital del Mar were classified as intracerebral haemorrhage (ICH) (n = 243) or ischaemic stroke (IS) (n = 1,043). IS was divided in non-lacunar stroke (NLS) (n = 732) and lacunar stroke (LS) (n = 311). Daily meteorological data were obtained from 'Observatori Fabra' of Barcelona: atmospheric pressure (AP), relative humidity, maximum, minimum, and mean temperatures, and the variation of all these measures compared with the previous day.

Results: Total stroke (TS) incidence showed little association with AP (coefficient of confidence, CC: -0.072; p = 0.022), but was higher with the AP variations (CC: 0.127; p < 0.001). NLS were related to AP falls (OR: 2.41; p < 0.001) whilst ICHs were associated with AP rises (OR: 2.07; p = 0.01). NLS and temperature showed an inverse correlation; however, it lost its significance after adjusting for AP variations. The daily incidences of NLS and ICH were higher in autumn and in winter, but depended strongly on the daily variations of AP. No other associations were found.

Conclusions: The incidences of NLS and ICH are related to AP changes compared with the previous day. AP changes largely explain the seasonal and daily variations in the incidence of stroke. These data may help to explain the controversy in previous studies and to promote studies focused on the trigger mechanisms of stroke.