 Over the course of eight decades, they visited homes, spoke to parents, siblings, tracked medical exams, followed marriages, careers. The study, which is now tracking a second generation of participants as well, has produced a wealth of significant data. However, in a recent article that was published in the Wall Street Journal, the director, Dr. Robert Wallinger, and associate director, Dr. Mark Schultz, pointed to the most significant contributing factor for physical health, mental health, and longevity, according to the data.