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It's interesting how drinking alcohol seems to have a J-curve for health effects. Light drinkers seem to do the best, but heavy drinkers do the worst of all groups (also see earlier posts). This research (published this week in the journal Stroke) shows that drinking more than 2 drinks a day in middle age is a bigger risk factor (double the risk) for a stroke between the ages of 60 to 75 years than high blood pressure, diabetes, or genetics. And once again, looking at the study one can see that nondrinkers had a small increased risk for stroke vs very light drinkers. From Science Daily:

Heavy drinking in middle-age may increase stroke risk more than traditional factors

Drinking more than two alcoholic beverages a day in middle-age raised stroke risks more than traditional factors such as high blood pressure and diabetes. Heavy drinking in mid-life was linked to having a stroke about five years earlier in life irrespective of genetic and early-life factors.

In a study of 11,644 middle-aged Swedish twins who were followed for 43 years, researchers compared the effects of an average of more than two drinks daily ("heavy drinking") to less than half a drink daily ("light drinking").

The study showed that: - Heavy drinkers had about a 34 percent higher risk of stroke compared to light drinkers. - Mid-life heavy drinkers (in their 50s and 60s) were likely to have a stroke five years earlier in life irrespective of genetic and early-life factors. - Heavy drinkers had increased stroke risk in their mid-life compared to well-known risk factors like high blood pressure and diabetes.At around age 75, blood pressure and diabetes appeared to take over as one of the main influences on having a stroke.

Researchers analyzed results from the Swedish Twin Registry of same-sex twins who answered questionnaires in 1967-70. All twins were under age 60 at the start. By 2010, the registry yielded 43 years of follow-up, including hospital discharge and cause of death data. ... Almost 30 percent of participants had a stroke. They were categorized as light, moderate, heavy or non-drinkers based on the questionnaires. 

Among identical twin pairs, siblings who had a stroke drank more than their siblings who hadn't had a stroke, suggesting that mid-life drinking raises stroke risks regardless of genetics and early lifestyle.

The study is consistent with the American Heart Association's recommended limit of two drinks a day for men and one for women. That's about 8 ounces of wine (two drinks) for a man and 4 ounces (one drink) for a woman. Regular heavy drinking of any kind of alcohol can raise blood pressure and cause heart failure or irregular heartbeats over time with repeated drinking, in addition to stroke and other risks.

Over the past year I have seen a number of studies looking at alcohol consumption and health effects. Overall it seems that the effects of alcohol are complex and frequently result in a J-curve: abstainers have a higher mortality rate or problems, light or moderate drinkers do the best, and then heavier drinkers have the most problems and higher mortality rates. The following two studies support this. From Science Daily:

Drinking moderate amounts of alcohol is linked to reduced risk of heart failure, large study finds

Evidence already exists for the beneficial effects of drinking moderate amounts of alcohol on the risk of developing a number of heart conditions; however, the role it plays in the risk of developing heart failure has been under-researched with conflicting results. Now, a large study of nearly 15,000 men and women shows that drinking up to seven drinks a week in early to middle age is associated with a 20% lower risk of men developing heart failure in the future when compared to people who did not drink at all, and a more modest 16% reduced risk for women.

They defined a drink as one that contains 14g of alcohol, equivalent to approximately one small (125ml) glass of wine, just over half a pint or a third of a litre of beer, and less than one shot of liquor such as whisky or vodka. The study participants were divided into six categories: abstainers (people who recorded having drunk no alcohol at every visit by the researchers), former drinkers, people who drank up to seven drinks a week, or between 7-14 drinks, 14-21 drinks, or 21 or more drinks a week.

From Science Daily:

If you're over 60, drink up: Alcohol associated with better memory

For people 60 and older who do not have dementia, light alcohol consumption during late life is associated with higher episodic memory -- the ability to recall memories of events -- researchers report.

Moderate alcohol consumption was also linked with a larger volume in the hippocampus, a brain region critical for episodic memory. The relationship between light alcohol consumption and episodic memory goes away if hippocampal volume is factored in, providing new evidence that hippocampal functioning is the critical factor in these improvements.

Findings from animal studies suggest that moderate alcohol consumption may contribute to preserved hippocampal volume by promoting generation of new nerve cells in the hippocampus. In addition, exposing the brain to moderate amounts of alcohol may increase the release of brain chemicals involved with cognitive, or information processing, functions.

Although the potential benefits of light to moderate alcohol consumption to cognitive learning and memory later in life have been consistently reported, extended periods of abusing alcohol, often defined as having five or more alcoholic beverages during a single drinking occasion is known to be harmful to the brain.