Ethnicity, At its Heart

Sonia Anand was perplexed. In 1997, the epidemiologist and MD at McMaster University found that when South Asians move to Canada, their risk of heart attack mysteriously spikes. Though heart disease is the number-one killer worldwide, the rate is 4 percent in rural India. When South Asians live in Canada, the rate jumps to 11 percent, which is double that of their white neighbors and almost six times as great as Chinese Canadians. Anand theorized that something in their new country is upping their chances for a heart attack.

It could be the shift to a fattier Western diet or new stressors in the lives of immigrants. But the fact that the same environment affects different ethnic groups in different ways had Anand asking a far broader question. At least...