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Background <p>Breast cancer (BC) is the leading cause of cancer in women worldwide with rising incidence in low- and middle-income countries (LMIC). We examined trends in reproductive and lifestyle factors for breast cancer across birth cohorts of Nigerian women.</p> Methods <p>We conducted a cross-sectional analysis of 2,309 female control participants (mean age, 42.5 ± 13.0 years) recruited between 1998 and 2017 as part of the Nigerian Breast Cancer Study (NBCS), an ongoing case-control study. Birth cohort was modeled as an ordinal predictor to evaluate temporal trends. Reproductive and lifestyle factors were analyzed across six birth cohorts (&lt; 1940, 1940–1949, 1950–1959, 1960–1969, 1970–1979, and ≥ 1980). Analyses of reproductive variables were repeated among women aged ≥ 40 years, and hormonal contraceptive use was additionally evaluated among women aged ≥ 30 years.</p> Results <p>Among all women, mean age at menarche declined from 16.0 years among women born before 1940 to 15.1 years among those born in or after 1980 (P for trend = 0.001), whereas age at thelarche remained stable across birth cohorts. Among women aged ≥ 40 years, mean parity declined from 6.1 to 4.1 live births, and cumulative lifetime breastfeeding duration decreased from 114 to 75 months (both P for trend &lt; 0.001). Mean breastfeeding duration per live birth showed only a modest decline. Among women aged ≥ 30 years, the prevalence of ever hormonal contraceptive use increased from 7.2% to 55.8% across birth cohorts (P for trend &lt; 0.001). Among all women, alcohol consumption remained low throughout (≤ 9% in every birth cohort).</p> Conclusions <p>Modest generational changes were observed in several reproductive and lifestyle factors traditionally associated with breast cancer risk among Nigerian women. These findings describe temporal changes in breast cancer risk factor profiles across successive birth cohorts. Future studies should examine environmental and other contextual exposures that may contribute to the evolving epidemiology of breast cancer in Nigeria and other low- and middle-income countries.</p>

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Birth cohort differences in reproductive and lifestyle breast cancer risk factors among women in the Nigerian breast cancer study

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Gideon T. Dosunmu,
  • Olasubomi Omoleye,
  • Dezheng Huo,
  • Mihai Giurcanu,
  • Yonglan Zheng,
  • Toshio F. Yoshimatsu,
  • Olufunmilayo I. Olopade

摘要

Background

Breast cancer (BC) is the leading cause of cancer in women worldwide with rising incidence in low- and middle-income countries (LMIC). We examined trends in reproductive and lifestyle factors for breast cancer across birth cohorts of Nigerian women.

Methods

We conducted a cross-sectional analysis of 2,309 female control participants (mean age, 42.5 ± 13.0 years) recruited between 1998 and 2017 as part of the Nigerian Breast Cancer Study (NBCS), an ongoing case-control study. Birth cohort was modeled as an ordinal predictor to evaluate temporal trends. Reproductive and lifestyle factors were analyzed across six birth cohorts (< 1940, 1940–1949, 1950–1959, 1960–1969, 1970–1979, and ≥ 1980). Analyses of reproductive variables were repeated among women aged ≥ 40 years, and hormonal contraceptive use was additionally evaluated among women aged ≥ 30 years.

Results

Among all women, mean age at menarche declined from 16.0 years among women born before 1940 to 15.1 years among those born in or after 1980 (P for trend = 0.001), whereas age at thelarche remained stable across birth cohorts. Among women aged ≥ 40 years, mean parity declined from 6.1 to 4.1 live births, and cumulative lifetime breastfeeding duration decreased from 114 to 75 months (both P for trend < 0.001). Mean breastfeeding duration per live birth showed only a modest decline. Among women aged ≥ 30 years, the prevalence of ever hormonal contraceptive use increased from 7.2% to 55.8% across birth cohorts (P for trend < 0.001). Among all women, alcohol consumption remained low throughout (≤ 9% in every birth cohort).

Conclusions

Modest generational changes were observed in several reproductive and lifestyle factors traditionally associated with breast cancer risk among Nigerian women. These findings describe temporal changes in breast cancer risk factor profiles across successive birth cohorts. Future studies should examine environmental and other contextual exposures that may contribute to the evolving epidemiology of breast cancer in Nigeria and other low- and middle-income countries.