Contrary to previous studies, a hard-driving type A personality may not increase the risk of heart disease, according to researchers who measured a number of cardiovascular and personality traits in thousands of Sardinians aged 14 to 102 years.

“The Sardinian population is quite isolated and very stable and shares a uniform environment. These features make it attractive to genetic studies,” Dr. Goncalo Abecasis of the University of Michigan, Ann Arbor told Reuters Health.

In initial analyses, they compared the overall genetic similarity of different individuals with their similarity for specific traits.

Results showed a clear genetic contribution to each of the 98 traits examined, including height, cholesterol levels, cardiovascular function, and personality.

Height was found to be 80 percent genetic, cholesterol about 40 percent, and behavior traits 10 to 20 percent.

“Interestingly, when we looked for evidence of genes that influence multiple traits, we found no evidence for genes that influence both personality and cardiovascular function,” Abecasis said.

However, more study is needed, the researcher cautioned, noting that “we are the first to look specifically for evidence of genes that affect these two different systems.”

The researchers also found evidence of genes that influence body weight and insulin levels, and weaker evidence that these genes play a role in blood pressure.

They also looked for differences in genetic effects in young and old individuals and found that, typically, genes made larger contributions to traits in younger individuals, but there were exceptions, such as blood pressure, where genetic effects only kick in later in life.

“The most exciting part of the study,” Abecasis said, “which corresponds to work we are carrying out right now, is to identify the specific genes involved in each of these traits. Our setup, with detailed characterization of many participants, should allow us to identify multiple genes simultaneously.”

SOURCE: PLoS Medicine September 2006.