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  3. While it’s widely accepted that drinking too much is bad for you, conventional wisdom — and the government’s dietary guidelines

While it’s widely accepted that drinking too much is bad for you, conventional wisdom — and the government’s dietary guidelines

admin2020-08-26  26
问题     While it’s widely accepted that drinking too much is bad for you, conventional wisdom — and the government’s dietary guidelines — say that alcohol can be consumed in moderation. The US government defines that as one drink a day for women and two for men. This study, published in the BMJ on Tuesday, finds that drinking around these levels — 8 to 12 drinks a week — is associated with a few measures of cognitive decline that showed up on brain scans.
    Researchers brought 550 Londoners to Oxford and ran them through an MRI machine. But these weren’t just any Londoners — they were government employees who, about every five years since 1985, had been filling out surveys about their health regimens, including how much alcohol they consumed. This enabled the researchers to look for relationships between the individuals’ drinking habits and what showed up on their brain scans.
    The researchers found that moderate drinking over those 30-plus years was associated with degeneration and shrinking of the hippocampus, a region of the brain involved in memory and navigation, and degeneration of the brain’s white matter. Consuming one more alcoholic drink per week was associated with a 0.01 percent decrease in the size of the hippocampus. For comparison, aging one year is associated with a 0.02 percent decrease.
    The study only looked at a few hundred Londoners, mostly well-educated and middle-class, so it may not be representative of a wider population. Topiwala, a psychiatry professor at the University of Oxford, pointed out there might have been "selection bias" in the sample — individuals had to get from London to Oxford in order to undergo the MRI scans and then spend an hour in a brain scanning machine and undergo other memory tests — which individuals who were alcohol dependent or had suffered brain damage from alcohol use might be less likely to do.
    In an accompanying editorial, Killian Welch, a neuropsychiatrist at a hospital in Scotland, wrote that the study might change what we think constitutes a healthy level of drinking. "The findings strengthen the argument that drinking habits many regard as normal have adverse consequences for health," Welch wrote. "This is important. We all use rationalizations to justify persistence with behaviors not in our long-term interest. With the publication of this paper, justification of ’ moderate’  drinking on the grounds of brain health becomes a little harder."
The study is questioned, because_________.
选项 A、the subjects are under stress when taking MRI
B、the sampling process is not scientific enough
C、the memory tests are not from authoritative sources
D、the alcoholics are likely to suffer brain damage
答案B
解析 本题是细节题，要求考生理解第四段人们对实验过程提出的质疑，即牛津大学精神病学教授指出样本中可能存在“选择偏见”。关键点：there might have been “selection bias” in the sample。
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