Experience in more than a quarter million women shows no significant association between use of powder in the genital area and ovarian cancer. The findings, published in JAMA, are from the largest study to date on this topic.
The conclusion was drawn by researchers based on a pool analysis of data from four large, US-based cohorts: Nurses’ Health Study (NHS), Nurses’ Health Study II (NHSII), Sister Study (SIS), and the Women’s Health Initiative Observational study (WHI-OS). The goal was to determine if there was a link between ever use of powder in the genital area and self-reported incident ovarian cancer. The new report includes updated data, more cases, and longer follow-up than the original research.
The authors noted that in the four studies, participants were asked about use of powder in the genital area in different ways. They therefore harmonized the data by categorizing the participants as having ever or never users. Long-term use was defined as at least 20 years or use at ages 10 to 13 years and also in the last year. Women were frequent users of powder if they had used in the genital area at least once a week, at least once a week in the last year, or “frequently” from ages 10 to 13.
Confounders in the four studies also were harmonized and included age at baseline, race, education, body mass index, parity, smoking status, hormone therapy use, and tubal ligation, hysterectomy, and menopausal status.
Across the studies, 39% of women commonly used powder in the genital area, with 53% ever use in WHI-OS, 41% in NHS, 27% in SIS, and 26% in NHSII. Rates of long-term use were 16% in WHI-OS and 6% in SIS and NHSII. Frequent use was reported by 27% of the women in NHS, 26% in NHSII, and 7% in SIS. The authors said that “there appeared to be a generational trend in use of powder in the genital area, with older cohorts more likely to report use.” Uses of powder also were more likely than non-users to be black (6% vs 3%), obese (26% vs 19%), and to be hysterectomized (22% vs 18%), and less likely to have used oral contraceptives (57% vs 64%).
Looking at incidence of ovarian cancer in the pooled sample, the authors found that among ever users, it was 61 cases per 100,000 person years versus 55 cases per 100,000 person years in women who had never used powder on their genital area. At age 70, the estimated risk difference was 0.09% (95% CI, -0.02% to 0.19%) and the estimated hazard ratio (HR) was 1.08 (95% CI, 0.99 to 1.17). The estimated HR for frequent vs never use was 1.09 (95% CI, 0.97 to 1.23) and for long-term vs never use, was 1.01 (95% CI, 0.82 to 1.25).
The researchers conducted subgroup analysis for 10 variables and none of the tests for heterogeneity were statistically significant for any of the comparisons. The estimated HR for the association between ever use of powder and ovarian cancer risk in women with a patent reproductive tract was 1.13 (95% CI, 1.01 to 1.26) but the P value for interaction comparing women with vs. without patent reproductive tracts was 0.15.
Commenting on how powder might affect reproductive organs, the authors said that their analysis and a possible positive association in women with patent reproductive tract “lends support to the hypothesis that powder with or without asbestos could irritate and inflame the reproductive tract.” They emphasized, however, that the finding should be considered exploratory and hypothesis generating. While concluding that their study showed no statistically significant association between self-reported use of powder in the genital area and incidence ovarian cancer, they also acknowledged that it was underpowered to identify a small increase in risk.