Air pollution may be a major cause of stroke, scientists have discovered. Up to now, pollutants in the air haven't been regarded as an important factor - but a group of scientists has discovered that everyone has been doing the wrong calculation.
Previous estimates have been based on the time the stroke victim arrives in hospital, but casting back just one day reveals a completely different picture.
The group reassessed the causes of stroke of 1101 patients admitted to a Boston hospital, and discovered that exposure to air pollutants became a major factor when the preceding 24 hours were also taken into account. The original statistics suggested that air pollutants were a factor in up to 34 per cent of cases, but this almost doubled to 63 per cent when the previous day's exposures were calculated back in.
Car exhaust fumes are a major cause of death in people who have survived a heart attack, a separate study has found. Exposure to relatively high levels for even two days was responsible for the deaths of 5.6 per cent of heart attack patients, scientists have discovered after studying the association among 25,000 heart attack survivors in five cities in Europe.
(Source: Epidemiology, 2009; 20: 137-42 (stroke study); 20: 110-8 (heart attack study)).