Forest or Trees? The Consequences of Aggregating Data from Diverse Populations

The concept of “social determinants of health” resonates with more people than ever before. Implicit in the phrase is that not everyone has equal access to healthcare, resulting in different outcomes in different populations. Complicating our understanding of these inequities is a less-than-granular way of looking at distinct populations. This point was highlighted in a recent analysis of rates of invasive second breast cancers (SBCs), either ipsilateral (ii) or contralateral (ic) following a diagnosis of ductal carcinoma in situ (DCIS) in Hawaii.

Investigators used the Hawaii Tumor Registry to identify 6221 women >20 years of age with a diagnosis of DCIS between 1973 and 2017. The population comprised: Japanese, 37%; white, 23%; Filipino, 14%; native Hawaiian, 13%; and Chinese, 8%. Often such studies aggregate populations as being, for instance, “Asian,” owing to the small numbers of distinct groups. In the entire study group, 444 women (7%) developed SBC: 190 had iiSBC and 254 had icSBC. Native Hawaiian and Filipino women had an increased likelihood of developing SBC compared to non-Hispanic whites. In addition, women <50 years and Japanese women were at increased risk of developing iiSBC.