Look at it this way. Too much stress on the body can lead to all kinds of ailments, including heart related. No exercise, proper eating, not drinking enough water - this all stresses the body. The human body wasn't designed to live off of alcohol. I wouldn't say directly alcohol causes strokes, but the lifestyle that comes with heavy drinking can surely contribute.
People who consume alcohol to intoxication often experience a hangover. Signs of increased sympathetic nervous system activity can accompany a hangover, including increased systolic blood pressure, rapid heartbeat (i.e., tachycardia), tremor, and sweating. For more information, see http://biology.about.com/library/weekly/aa010104a.htm
Alcohol can also interfere with the function of blood pressure medication. Elevated blood pressure is a primary risk factor in inducing stroke.
Yes. Continued consumption of large amounts of alcohol increases blood pressure, which is a primary risk factor for stroke.
My husband had 3 TIAs (mini-strokes) at age 40.
His bp before that was 180/120. His dr prescribed meds, and they only brought it down to 160/100-110.
He quit drinking finally after a violent incident (or told me he quit, actually was still sneaking it occassionally but at a much lower level) and his bp dropped to 110/60.
In the past few months he's started drinking increasingly heavily again and his bp was back up, still on meds, to 130/84 a month ago. Still not terrible, but rising as his alcohol intake increases. He doesn't see the correlation.
Unlike your parents, he is a binge drinker - huge volumes all at once, sometimes a 2-3 day binder in which he may consume 60-70 drinks. What your parents are doing is at a far lower level, but still more than what is considered safe. There could certainly be a correlation.