1. Epidemiology and Global Health
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Sense of coherence and risk of breast cancer

  1. Kejia Hu
  2. Mikael Eriksson
  3. Yvonne Wengström
  4. Kamila Czene
  5. Per Hall
  6. Fang Fang  Is a corresponding author
  1. Unit of Integrative Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Sweden
  2. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Sweden
  3. Department of Neurobiology, Care Sciences and Society, Karolinska Institutet & Theme Cancer, Karolinska University Hospital, Sweden
Research Article
Cite this article as: eLife 2020;9:e61469 doi: 10.7554/eLife.61469
2 figures, 3 tables and 3 additional files

Figures

Linear associations between sociodemographic and lifestyle factors and sense of coherence.

Abbreviations: BMI: body mass index; LCI: lower boundary of 95% confidence interval; UCI, upper boundary of 95% confidence interval. : Continuous variable. European ancestry was defined as if the participant and her parents were all born in Europe. § Physical activity was categorized by tertiles of the metabolic equivalent of task of daily physical activity during the last month.

Time-dependent effect of sense of coherence on incident breast cancer.

Abbreviations: SoC, sense of coherence. Time-varying hazard ratios of incident breast cancer for moderate and strong SoC compared to weak SoC were derived from a flexible parametric model, adjusted for sociodemographic factor (age, ancestry, education), lifestyle factors (body mass index, smoking, alcohol consumption, physical activity), and known risk factors for breast cancer including reproductive and hormonal factors (age at menarche, age at first birth, No. of pregnancies, No. of births, use of contraceptives, use of hormone replacement therapy, menopausal status), as well as family history of breast cancer, benign breast disorders, other malignancies, and breast density.

Tables

Table 1
Characteristics of study participants by sense of coherence at baseline.
CharacteristicsWeak SoC *Moderate SoCStrong SoC
No.16,06616,09914,271
Age at baseline, mean [SD]54.0 [9.7]55.1 [9.8]55.6 [9.9]
European ancestry (%)15,341 (95.5)15,726 (97.7)13,970 (97.9)
Education, years (%)
≤102412 (15.0)2143 (13.3)1885 (13.2)
125500 (34.2)4776 (29.7)3744 (26.2)
>127767 (48.3)8829 (54.8)8330 (58.4)
Body mass index (Kg/m2), mean [SD]25.6 [4.5]25.1 [4.1]25.0 [4.0]
Smoking (%)
Never7028 (43.7)7663 (47.6)7285 (51.0)
Previous6569 (40.9)6481 (40.3)5535 (38.8)
Current2430 (15.1)1927 (12.0)1430 (10.0)
Alcohol consumption (%)
Non-drinker3628 (22.6)2700 (16.8)2373 (16.6)
<10 g/d9121 (56.8)10,013 (62.2)9136 (64.0)
≥10 g/d3168 (19.7)3259 (20.2)2681 (18.8)
Physical activity (%)
Low5926 (36.9)5371 (33.4)4486 (31.4)
Medium5077 (31.6)5489 (34.1)4947 (34.7)
High4873 (30.3)5146 (32.0)4769 (33.4)
Age at menarche, mean [SD]13.1 [1.5]13.1 [1.5]13.1 [1.4]
Age at first birth, mean [SD]27.0 [5.5]27.2 [5.2]27.2 [5.1]
No. of pregnancies, median (range)2 (0–15)2 (0–13)2 (0–15)
No. of births, median (range)2 (0–11)2 (0–11)2 (0–11)
Ever use of oral contraceptives (%)13,429 (83.6)13,549 (84.2)12,018 (84.2)
Ever use of HRT (%)4407 (27.4)4362 (27.1)3752 (26.3)
Post-menopausal (%)8590 (53.5)9294 (57.7)8476 (59.4)
BC in first degree relatives (%)2002 (12.5)2006 (12.5)1821 (12.8)
Benign breast disorders (%)3653 (22.7)3659 (22.7)3143 (22.0)
Other malignancies (%)856 (5.3)882 (5.5)799 (5.6)
Breast density, mean [SD]22.0 [19.5]22.4 [19.7]22.1 [19.3]
  1. Abbreviations: BC, breast cancer; HRT, hormone receptor therapy; SD, standard deviation; SoC, sense of coherence.

    *: SoC was categorized according to tertiles of the total SoC score measured at baseline for all women.

  2. : Breast density (%) was calculated using absolute dense area (cm2) divided by total breast area (cm2) using STRATUS software.

Table 2
Hazard ratios and 95% confidence intervals of breast cancer in relation to sense of coherence measured at baseline.
SoC1000 PYsEvent (IR)Model 1*Model 2
In three categories
Weak SoC83251 (3.0)1.001.00
Moderate SoC83264 (3.2)1.05 (0.88–1.25)1.00 (0.84–1.19)
Strong SoC74256 (3.5)1.15 (0.97–1.37)1.08 (0.90–1.29)
Per SD increase§240771 (3.2)1.11 (1.03–1.20)1.08 (1.00–1.17)
  1. Abbreviations: PYs, person-years; IR, incidence rate per 1000 person-years; SoC, sense of coherence; SD, standard deviation.

    *: Estimates were not adjusted for any covariate. : Estimated were adjusted for sociodemographic factors (age, ancestry, education) and lifestyle factors (body mass index, smoking, alcohol consumption, physical activity), and known risk factors for breast cancer including reproductive and hormonal factors (age at menarche, age at first birth, No. of pregnancies, No. of births, use of contraceptives, use of hormone replacement therapy, menopausal status), as well as family history of breast cancer, benign breast disorders, other malignancies, and breast density.

  2. : Total SoC score at baseline was calculated and categorized as weak, moderate, and strong according to tertile distribution of all women. §: SoC was treated as a continuous variable after standardization using z-score method.

Table 3
Hazard ratios and 95% confidence intervals of breast cancer subtypes in relation to sense of coherence measured at baseline.
Subtypes*Weak SoCModerate SoCStrong SoC
1000 PYsEvent (IR)HR1000 PYsEvent (IR)HR (95% CI)1000 PYsEvent (IR)HR (95% CI)
Luminal A83105 (1.3)Ref.8399 (1.2)0.91 (0.69–1.20)74100 (1.4)1.05 (0.79–1.39)
Luminal B18317 (0.2)Ref.8322 (0.3)1.23 (0.65–2.34)7412 (0.2)0.63 (0.30–1.34)
Luminal B28312 (0.1)Ref.8314 (0.2)1.28 (0.58–2.80)7415 (0.2)1.47 (0.67–3.23)
Triple-negative839 (0.1)Ref.8315 (0.2)1.52 (0.66–3.50)746 (0.1)0.71 (0.24–2.04)
HER2-enriched839 (0.1)Ref.838 (0.1)0.78 (0.30–2.06)747 (0.1)0.82 (0.30–2.28)
Unclassified8399 (1.2)Ref.83106 (1.3)0.99 (0.75–1.31)74116 (1.6)1.23 (0.93–1.62)
  1. Abbreviations: PYs, person-years; IR, incidence rate per 1000 person-years; SoC, sense of coherence.

    *: Breast cancer subtypes were classified based on estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). Luminal A: ER+, PR+, HER2-; Luminal B1: ER+, PR-, HER2-; Luminal B2: ER+, HER2+; Triple-negative: ER-, PR-, HER2-; HER2-enriched: ER-, PR-, HER2+; the rest were unclassified, mostly because of undetermined HER2 status.

  2. : A total SoC score at baseline was calculated and categorized according to tertiles in all women: weak, moderate, and strong. : Estimates were adjusted for sociodemographic factor (age, ancestry, education), lifestyle factors (body mass index, smoking, alcohol consumption, physical activity), and known risk factors for breast cancer including reproductive and hormonal factors (age at menarche, age at first birth, No. of pregnancies, No. of births, use of contraceptives, use of hormone replacement therapy, menopausal status), as well as family history of breast cancer, benign breast disorders, other malignancies, and breast density.

Additional files

Source code 1

Stata script for Table 2 and Figure 2.

https://cdn.elifesciences.org/articles/61469/elife-61469-code1-v2.do.zip
Supplementary file 1

SoC-13 questionnaire of sense of coherence used in the Karolinska Mammography Project for Risk Prediction of Breast Cancer (Karma) cohort.

The following questions were asked to investigate how the participants experienced these situations. A 7-point Likert-type scale is used to answer each question, with one corresponding to ‘very seldom or never’, and seven corresponding to ‘very often’. To simplify the structure, the answer of item 4 to 9, 11 to 13 have been reversed on the basis of the original SoC-13 questionnaire.

https://cdn.elifesciences.org/articles/61469/elife-61469-supp1-v2.pdf
Transparent reporting form
https://cdn.elifesciences.org/articles/61469/elife-61469-transrepform-v2.docx

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