Smoking linked to bleeding in the brain in large, long-term study of
twins

Date:
September 17, 2020
Source:
American Heart Association
Summary:
Researchers in Finland found a link between smoking and subarachnoid
hemorrhage (SAH), a type of bleeding stroke, in a study of more than
16,000 pairs of twins over 42 years. The study found that bleeding
in the brain can be explained to a greater degree by environmental
risk factors, such as smoking, than by genetic influence.



FULL STORY ==========================================================================
An investigation of the Finnish Twin Cohort reaffirmed a link between
smoking and subarachnoid hemorrhage (SAH), a type of bleeding stroke
that occurs under the membrane that covers the brain and is frequently
fatal. The new study by researchers in Finland is published today in
Stroke, a journal of the American Stroke Association, a division of the American Heart Association.


==========================================================================
In a 2010 study of nearly 80,000 twins from Denmark, Finland and Sweden, results suggested that SAH had more to do with external risk factors
and very little to do with genetic influence. Twins share either all
or half their genes (identical vs. fraternal) so they are valuable for
studies designed to evaluate the role of genetics versus environmental
factors in disease development.

In this study, researchers sought to clarify the factors involved when
only one twin suffered from fatal bleeding in the brain and hypothesized
that smoking - - the most important environmental risk factor -- could
play a significant role. This study utilized health care data from the
Finnish Twin Cohort, a national database of 32,564 individuals (16,282 same-sex, twin pairs in Finland) who were born before 1958 and alive in
1974, and followed for over 42 years between 1976 and 2018. Researchers identified 120 fatal bleeding stroke events among the twins, and the
strongest link for a fatal brain bleed was found among smokers.

"Our study provides further evidence about the link between smoking and bleeding in the brain," said corresponding researcher Ilari Rautalin,
B.M., a sixth-year medical and Ph.D. student at the University of Helsinki
in Finland.

Data collected from surveys included smoking; high blood pressure
(diagnosis or use of antihypertensive medications); physical activity;
body mass index; education; and alcohol use. Participants were separated
into two groups: smokers (occasional or current) or non-smokers (never
and former). Current smokers were classified according to the number of cigarettes smoked per day: light, less than 10; moderate, 10-19; heavy,
20 or more.

The analysis of the 120 fatal bleeding events found: Four fatalities
occurred among both twins in two pairs. In the remaining 116 fatalities,
one twin died of bleeding in the brain, while the other died of another
cause, migrated during the follow-up or was still alive at the end of
the study follow-up.

Heavy and moderate smokers had 3 times the risk of fatal bleeding in
the brain, while light smokers had slightly less at 2.8 times the risk.

Median age at the fatal brain bleed was 61.4 years.

Risk factors such as high blood pressure, lower physical activity
rates and being female were not found to be significant influences in
this investigation, unlike prior studies. Smoking was associated with
fatal bleeding in the brain consistently in both men and women and with bleeding stroke deaths within twin pairs where only one of the twins
died from a SAH.

The current study did not have data on non-fatal SAH events and
researchers were not able to estimate the impact of former smoking on
these brain bleeds.

Former smokers and never smokers were combined in the non-smoking
category.

Researchers were also not able to confirm the aneurysmal origin of SAHs
(no patient data was available) and may have included a few non-aneurysmal
SAH events.

"This long-term study in twins helps to confirm the link between
subarachnoid hemorrhage and smoking," said Rose Marie Robertson, M.D.,
FAHA, the American Heart Association's deputy chief science and medical
officer and co-director of the AHA Tobacco Center for Regulatory Science,
who was not involved in the study. "Not smoking or quitting if you've
already started, is an essential component of primary prevention."

========================================================================== Story Source: Materials provided by American_Heart_Association. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ilari Rautalin, Miikka Korja, Jaakko Kaprio. Smoking Causes Fatal
Subarachnoid Hemorrhage. Stroke, 2020; DOI:
10.1161/STROKEAHA.120.031231 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200917084557.htm

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