ANN ARBOR—Although human genes contribute significantly to a person’s health and behavior, these two kinds of traits aren’t closely linked at all.

In fact, a study appearing this month in the Public Library of Science found absolutely no connection between the hard-driving personality and heart disease, contrary to previous studies and conventional wisdom.

This is among the first findings of a massive, 10-year effort to measure the genes and traits of a single population of closely related people. Conducted jointly by Italian and Sardinian researchers, the U.S. National Institute on Aging, and bio-statisticians at the University of Michigan, the project recruited 6,148 people aged 14 to 102 in four clustered villages on the island of Sardinia in the Mediterranean Sea. The sample represents 62 percent of the population of the Lanusei Valley surrounding the four villages.

Sardinia was chosen as an ideal laboratory for genetic studies because of its isolation and relative stability, said Gon