What is the cause and result of the roseto mystery? what overarching idea is gladwell establishing in his introduction?

Roseto, a town in Pennsylvania. People of the town are mostly Obese but the occurrence of heart disease in them are very low. This amazed the doctors and they performed every kind of tests but this became a mystery. 
The result of the mystery was the social culture of the community.
People of the town happily lived together, sometimes three generations of a family would live under one roof, all are good with their neighbors and chat with them.

Americans often speak of their country as one of several large regions.  these regions are cultural units rather than governmental units --  formed by history and geography and shaped by the economics, literature and folkways that all the parts of a region share. what makes one region different from another? a region's multicultural heritage as well as distinct demographic characteristics like age and occupation make regions different and special. within several regions, language is used differently and there are strong dialects. there are also differences in outlook and attitude based on geography.