Researchers analyzed telephone interviews and laboratory results from 990 people between the ages of 40 and 70 and found that optimists were less likely to have higher levels of bad cholesterol (i.e. LDL) and higher levels of good cholesterol (i.e. HDL), which protected the heart and helped counteract bad cholesterol. Therefore, the study believes that mental health and physical health are closely related to another evidence that optimistic temperament may have some real benefits for human health.
The statement "The study did not find a reason for the link between optimism and total cholesterol levels" best supports the above research conclusion.