Lower breast cancer risk among women with two Hakka parents in Taiwan: A nationwide population-based study.

BACKGROUND

Breast cancer is the most common cancer among women in Taiwan, yet most epidemiological studies treat Taiwanese Han women as a homogeneous population. Whether breast cancer occurrence differs across major Han subgroups, such as Hakka and Min-nan, remains insufficiently explored.

METHODS

We conducted a nationwide, population-based study by linking the Taiwan Biobank (TWB) with the National Cancer Registry (NCR) and the National Health Insurance Research Database (NHIRD). A total of 78,530 women aged 30-70 years were included, comprising 879 breast cancer cases and 77,651 controls. Parental ethnic/dialect background was determined by the self-reported ethnicity of both parents and categorized as Min-nan, Hakka, or Mainland Chinese. Multivariable logistic regression models were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for breast cancer risk associated with parental ethnicity, adjusting for demographic characteristics, lifestyle behaviors, reproductive factors, family history of breast cancer, and metabolic comorbidities.

RESULTS

After multivariable adjustment, women with two Hakka parents had a significantly lower odds of breast cancer compared with those with two Min-nan parents (aOR, 0.75; 95% CI, 0.60-0.95). No significant associations were observed for other parental ethnic combinations. Advancing age was strongly associated with increased breast cancer risk, as was diabetes mellitus (aOR, 1.28; 95% CI, 1.07-1.52). A family history of breast cancer in first-degree relatives, including mothers and sisters, was also independently associated with higher odds. Lifestyle factors, anthropometric measures, and reproductive variables showed no significant associations after adjustment.

CONCLUSIONS

In this nationwide cohort, breast cancer occurrence differed within the Taiwanese Han population, with a lower risk observed among women with Hakka ancestry on both parental sides. These findings highlight meaningful within-population heterogeneity and underscore the importance of considering ethnic and cultural subgroups in breast cancer epidemiology and risk stratification.