In total, the study received responses from 1899 breast cancer patients and survivors, with 68.5% of them responding to at least two waves of surveys. Of the responders, 1317 (69.4%) were non-Hispanic White (“White”), 450 (23.7%) were non-Hispanic Black (“Black”), 53 (2.8%) were Hispanic, 75 (4.0%) were Asian and 2 (0.1%) were Native Americans. As numbers in racial/ethnic groups other than Black and White were small, most of the further analyses on racial disparities included Black and White patients. The median time from diagnosis to first survey was 5.1 years (IQR: 2.3-9.2), with only 7.8% of the patients diagnosed within 1 year before their first survey response.
Black patients were more likely to be diagnosed at older ages, with triple-negative breast cancer, at later stages, and with higher comorbidity burden (Table 1). In terms of the SES factors, Black patients were much more likely to be on Medicaid (18.0% vs. 1.4%; P < .001), be single or never married (28.2% vs. 6.3%; P < .001), have less education, and have lower levels of annual household income. Black patients were also more likely to live in neighborhoods with lower SES in terms of income and education level, which was also captured by more disadvantaged ADI.
Social Isolation and Stress
Overall, the isolation/stress level was moderate (Fig 1). For White patients, the average isolation/stress score significantly improved from 2020 to 2022, declining from 13.1 to 12.2 to 11.6 (P-trend < .001). As for Asian patients, despite a small sample size (n = 75), the isolation/stress score has also significantly improved (P-trend = .044). However, this positive trend was not seen for Black patients, with the average score in the three waves of surveys being 12.8, 13.6 and 12.6, respectively (P-trend = .84). Hispanic patients had the highest isolation/stress scores throughout the three waves of surveys, although the 95%CI was wide due to limited sample size (n = 53).
Delving deeper into the individual questions of the total isolation/stress score can help us pinpoint the exact areas where these disparities presented (Supplemental Table 1). White patients felt significantly more confident than Black patients in getting medical help and keeping up with work and home responsibilities in all three waves of surveys. On the other hand, Black patients were significantly more likely to feel isolated, overwhelmed, and worried about getting COVID in the 2021 survey, and were significantly more likely to worry about going to hospitals in 2021 and 2022. In addition, more patients on Medicaid expressed “Often” or “Always” being worried about the need to go to hospital compared to patients covered by private insurance in all three years (15.6% vs. 8.4% in 2020, 26.0% vs. 9.5% in 2021, and 18.2% vs. 7.1% in 2022; all P < .05).
Mixed-effects models showed similar findings as the descriptive analysis (Table 2). The isolation/stress score significantly decreased each year for White patients, while an improvement was only observed for Black patients in the last wave of survey and there was a statistically significant interaction between racial group and survey years (P < .001). The unadjusted differences in isolation/stress scores between Black and White patients was 1.34 (95%CI: 0.57, 2.10) in 2021 and 1.14 (95%CI: 0.34, 1.95) in 2022. Individual-level SES factors were significantly associated with both race/ethnicity and the isolation/stress score, and after adjustment of SES factors, the racial differences in the last two waves of surveys were not statistically significant. Patients on Medicaid had a higher isolation/stress score by 2.81 (95%CI: 1.39, 4.23) compared with those covered by private insurance. Patients who were younger, single or never married, without a high school degree, and with annual household income of <$35,000 also had significantly higher isolation/stress scores. No associations were found between the isolation/stress score and years since breast cancer diagnosis, tumor characteristics, or comorbidities.
Decomposing the total isolation/stress score into the social isolation score and the stress score found that they were associated with different individual-level SES factors (Supplemental Table 2). Specifically, the social isolation score was significantly associated with marital status and the number of people living in the same household, with patients being married and patients living with more people having significantly lower levels of social isolation. Whereas for the stress score, it was significantly associated with insurance type and education level. The racial differences observed in the two scores were no longer statistically significant after adjusting for the relevant individual-level SES factors.
Sensitivity Analysis
To account for the missing values in annual household income and education level, we conducted multiple imputation. The main findings remained consistent in the imputed datasets (Supplemental Table 3). The isolation/stress score for White patients significantly decreased from 2020 to 2022 (P < .001), but no statistically significant changes were found for Black patients. The racial differences were not significant in all three waves of survey, after adjusting for the imputed annual household income in addition to age at diagnosis and years to first survey.
Sleep Quality
Through examining the ISI, we found that more than 48% of the patients had clinically-significant insomnia (ISI ≥ 8). Of these, 16.2% of Black patients and 11.3% of White patients suffered from moderate to severe insomnia (ISI ≥ 15). As we hypothesized, more severe insomnia was significantly associated with higher isolation/stress scores in all three waves of surveys (Supplemental Fig 2). More severe insomnia was also strongly associated with younger age at survey (OR = 1.24 per 10-year decrease in age; 95%CI: 1.13, 1.36) and lower annual household income (OR = 4.50 [comparing <$35,000 to ≥$200,000]; 95%CI: 1.96, 10.17). In terms of responses to the individual ISI questions (Supplemental Table 4), Black patients aged <65 years were significantly more likely to report having difficulty in falling asleep (P = .022) and problems waking up too early (P = .029).
In terms of sleep time, the two measurement methods demonstrated moderate consistency (Pearson's correlation = 0.57; concordance = 0.44), with self-reported average sleep time being around one hour shorter than self-reported wake-bed time differences (Table 3). Despite this discrepancy, our subsequent results were reported based on self-reported average sleep time, as both methods yielded similar conclusions. White patients had significantly longer hours of sleep than Black patients on average (7.0 vs. 6.3 hours/day, P < .001), with patients aged ≥65 years having slightly longer sleep time. Black patients were significantly more likely to sleep for less than 6 hours/day compared to White patients, after adjusting for age (OR = 3.24; 95%CI: 2.22, 4.72). Among patients younger than 65 years old, Black patients needed significantly longer time to fall asleep compared to White patients (30 vs. 20 minutes, P = .005), which was consistent with our observation from the analysis of individual ISI questions.