Even though
ulcers appear to run in families, lifestyle plays more of a role than genetic
factors in causing the illness, according to a report in the April 13th
Journal of Internal Medicine. In particular, smoking and stress in men
and the regular use of pain-releasing medicines in women were linked with an
increased risk of developing an ulcer. Overall, 61% of ulcer
risk appears to be due to environmental factors, such as smoking, and the
remaining 39% is due to genes according to Dr.Ismo Raiha of the University of
Turky and colleagues at the University of Helsinki, Finland. Some researchers
had suggested that families may spread Helicobacteria pylori, the bacteria that
can cause ulcers. However, the new study suggests this is unlikely, according to
the report. Raiha and colleagues studied data from more than
13,000 pairs of twins "to examine the roles of genetic and environmental factors
in the origin of peptic ulcer disease," they explain. Both twins were more
likely to develop an ulcer if the pair were genetically the same as compared
with a pair of fraternal twins, suggesting that there must be some genetic
susceptibility to ulcer development. However, the risk was no
greater in twins living together compared with twins living apart, suggesting
that shared exposure to H. pylori was not to blame. "Environment effects were
not due to factors shared by family members, and they were related to smoking
and stress in men and the use of analgesics in women," the authors wrote. "The
minor effects of shared environment to disease liability do not support the
concept that the grouping of risk factors, such as H. pylori infection, would
explain the genetic factor of peptic ulcer disease," they concluded.
单选题
According to the passage, which of the following is a very likely cause
of ulcer in men?