Changing patterns of breast cancer incidence and mortality by education level over four decades in Norway, 1971-2009.
In the last century, breast cancer incidence and mortality was higher among higher versus lower educated women in developed countries. Post-millennium, incidence rates have flattened off and mortality declined. We examined breast cancer trends by education level, to see whether recent improvements in incidence and mortality rates have occurred in all education groups.



We linked individual registry data on female Norwegian inhabitants aged 35 years and over during 1971–2009. Using Poisson models, we calculated absolute and relative educational differences in age-standardised breast cancer incidence and mortality over four decades. We estimated educational differences by Slope and Relative Index of Inequality, which correspond to rate difference and rate ratio, comparing the highest to lowest educated women.



Pre-millennium, incidence and mortality of breast cancer were significantly higher in higher versus lower educated women. Post-millennium, educational differences in breast cancer incidence and mortality attenuated. During 2000–2009, breast cancer incidence was still 38% higher for higher versus lower educated women (Relative Index of Inequality: 1.38, 95% confidence interval: 1.31–1.44), but mortality no longer varied significantly by education level (Relative Index of Inequality: 1.09, 95% confidence interval: 0.99–1.19). Among women below 50 years, however, the education gradient for mortality reversed, and mortality was 28% lower for the highest versus lowest educated women during 2000–2009 (Relative Index of Inequality: 0.72, 95% confidence interval: 0.51–0.93).



Post-millennium improvements in breast cancer incidence and mortality have primarily benefited higher educated women. Breast cancer mortality is now highest among the lowest educated women below 50 years.
Department of Research, Cancer Registry of Norway, Oslo, Norway.|Norwegian Advisory Unit for Women's Health, Oslo University Hospital, Oslo, Norway.|Department of Health and Inequality, Norwegian Institute of Public Health, Oslo, Norway.
Cassia B
CB
Trewin
Department of Ageing and Health, Norwegian Institute of Public Health, Oslo, Norway.|Department of Community Medicine, Institute of Health and Society, University of Oslo, Oslo, Norway.
Bjørn Heine
BH
Strand
Oslo Centre for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway.
Harald
H
Weedon-Fekjær
Cancer Registry of Norway, Institute of Population-based Cancer Research, Oslo, Norway.|Department of Preventative Medicine, University of Southern California, Los Angeles, USA.|Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
Giske
G
Ursin
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000401:mortality*; D002423:Cause of Death / Q000639:trends*; D004522:Educational Status; D005260:Female; D054624:Health Status Disparities; D054625:Healthcare Disparities; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009026:Mortality / Q000639:trends*; D009664:Norway / Q000453:epidemiology; D011159:Population Surveillance; D012042:Registries; D012959:Socioeconomic Factors