“Tooth loss and gum disease, which is inflammation (发炎) of the tissue around the teeth that can cause shrinkage (萎缩) of the gums and loosening of the teeth, are very common, so evaluating a potential link with brain diseases is incredibly important. Our study found that these conditions may play a role in the health of the brain area that controls thinking and memory, giving people another reason to take better care of their teeth,” said study author Satoshi Yamaguchi, Ph.D. of Tohoku University in Sendai, Japan.

The study involved 172 people with an average age of 67 who did not have memory problems at the beginning of the study. Researchers found that the number of teeth and amount of gum disease was linked to changes in the left hippocampus of the brain. For people with mild gum disease, having fewer teeth was associated with a faster rate of brain shrinkage, which was the same for people with severe gum disease having more teeth. After adjusting for age, researchers found that for people with mild gum disease, the increase in the rate of brain shrinkage due to one less tooth was equal to nearly one year of brain aging. By contrast, for people with severe gum disease, the increase in brain shrinkage due to one more tooth was equal to 1.3 years of brain aging.

“These results highlight the importance of preserving the health of the teeth and not just maintaining the teeth,” Yamaguchi said. Though the study does not prove that gum disease or tooth loss causes diseases like Alzheimer’s, it only shows an association. Yamaguchi added, “Future studies are needed with larger groups of people.” The current experiment involved only a small group of people in one region of Japan, and that too from one particular region of the world.

【小题1】What does Satoshi Yamaguchi’s research focus on?

A．The reason for gum disease.

B．The influence of brain shrinkage.

C．The advances in memory improvement.

D．The link between dental health and brain.

【小题2】What is paragraph 2 mainly about?

A．Supporting evidence for the research results.

B．Basic theories and results of a previous research.

C．A further explanation of the research methods.

D．The detailed procedures of the scientific research.

【小题3】What does Yamaguchi suggest people do?

A．Treat a brain problem with replacing teeth.

B．Frequently visit the dentists to maintain teeth.

C．Protect gums and teeth in their original good state.

D．Pull out one of their unique teeth as a study object.

【小题4】What probably can be involved in the follow-up study?

A．The application in related fields.

B．The further research in wider range.

C．The difficulties of making the previous studies.

D．The suggestions for preventing teeth disease.