Decrease in smoking related to stroke?

Looks like Finland's national tobacco policies have radically reduced the incidences of subarachnoid haemorrhage, the most fatal form of stroke.

Previously, it was thought that in Finland approximately a thousand people suffer subarachnoid haemorrhage (SAH) every year - most of them adults of working age. Up to half of those afflicted die within a year.

Subarachnoid haemorrhage is typically caused by a ruptured cerebral aneurysm, which leads to a sudden increase in the intracranial pressure. Smoking is a key risk factor for SAH.

A University of Helsinki study looked at changes in the incidences of subarachnoid haemorrhage over a period of 15 years (1998-2012) and these were contrasted with changes in the prevalence of smoking.

The results indicated that the number of people afflicted with SAH was nearly half of the previously assumed figure and that the number was in rapid decline, a trend which was particularly apparent in younger generations.

Within fifteen years, the prevalence of SAH had decreased by 45 percent among women and 38 percent among men under 50 years of age. During the same period, the prevalence of SAH decreased by 16 percent among women and 26 percent among men over 50.

Smoking among Finns aged 15-64 decreased by 30 percent during the monitoring period.

"It is extraordinary for the incidence of any cardiovascular disease to decrease so rapidly at the population level in such a short time," said researcher Jaakko Kaprio from the University of Helsinki.

"Even though we cannot demonstrate a direct causation in nation-wide studies, it is highly likely that the national tobacco policies in Finland have contributed to the decline in the incidence of this type of severe brain haemorrhage," he added.

Cerebral aneurysms are present in up to more than 10 percent of people over the age of 70, but most of them never rupture. For decades, the researchers have been searching for factors, which could be used to identify persons at high risk of aneurysm ruptures and who should consequently be treated.

"Previous studies have indicated that smoking is one of the most important susceptibility factors for rupturing aneurysms, so in that sense the now established connection between a decrease in smoking and a decrease in SAH is not surprising," said another researcher Miikka Korja.

This study has been published in Neurology.