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Table 1 Descriptive characteristics of the study population

From: Long-term exposure to insulin and volumetric mammographic density: observational and genetic associations in the Karma study

Characteristic Matched cohort analysis insulin-treated diabetes Insulin genetic score analysis
Insulin-treated T1D (n = 122) Non-diabetics (n = 610) P value Insulin-treated T2D (n = 237) Nondiabetics (n = 1161) P value Nondiabetics (n = 9437)
Age, years, mean (SD) 49.6 (8.6) 49.6 (8.5) 1.00 62.5 (8.0) 62.3 (7.9) 0.82 57.3 (9.8)
BMI, kg/m2, mean (SD) 25.7 (4.3) 25.1 (4.3) 0.17 29.5 (5.7) 25.3 (3.9) <  0.001 25.3 (4.1)
Education level, % (n)    0.09    0.09  
 Compulsory 8.5 (10) 8.3 (49)   27.9 (62) 22.7 (250)   16.9 (1376)
 Gymnasium 40.2 (47) 30.2 (178)   29.7 (66) 27.2 (300)   31.2 (2544)
 University 51.3 (60) 61.5 (362)   42.3 (94) 50.1 (552)   51.9 (4234)
 Missing 4.1 (5) 3.4 (21)   6.3 (15) 5.1 (59)   13.6 (1283)
Age at menarche, years, mean (SD) 13.4 (2.0) 13.0 (1.4) 0.02 12.8 (1.5) 13.3 (1.5) <  0.001 13.2 (1.5)
Parity, % (n)    <  0.001    0.12  
 0 22.1 (27) 14.0 (85)   17.9 (42) 12.6 (144)   12.1 (1129)
 1 25.4 (31) 14.0 (85)   14.5 (34) 12.9 (147)   14.5 (1354)
 2 36.9 (45) 51.8 (314)   42.7 (100) 46.8 (534)   47.6 (4460)
  ≥ 3 15.6 (19) 20.1 (122)   24.8 (58) 27.8 (317)   25.9 (2423)
 Missing 0.0 (0) 0.7 (4)   1.3 (3) 1.6 (19)   0.8 (71)
Age at first birth, years, mean (SD) 27.3 (5.6) 28.5 (5.3) 0.05 24.3 (4.4) 25.8 (5.0) <  0.001 26.6 (5.0)
 Missing 5.3 (5) 5.6 (29)   6.3 (12) 5.1 (51)   
Menopausal status, % (n)    0.97    0.86  
 Premenopausal 65.6 (80) 65.4 (399)   13.5 (32) 14.0 (162)   34.1(3216)
 Postmenopausal 34.4 (42) 34.6 (211)   86.5 (205) 86.0 (999)   65.9 (6221)
OC use (ever), % (n) 73.8 (90) 85.6 (519) 0.001 66.1 (154) 75.3 (853) 0.004 79.0 (6779)
 Missing 0.0 (0) 0.7 (4)   1.7 (4) 2.4 (28)   9.1 (857)
HRT, % (n)    0.23    0.52  
 Never 86.8 (99) 86.9 (504)   71.2 (151) 70.6 (730)   73.6 (6400)
 Former 7.9 (9) 10.5 (61)   25.5 (54) 24.3 (251)   21.9 (1909)
 Current 5.3 (6) 2.6 (15)   3.3 (7) 5.1 (53)   4.8 (423)
 Missing 6.6 (8) 4.9 (30)   10.5 (25) 10.9 (127)   7.5 (705)
Alcohol intake, % (n)    0.02    <  0.001  
 None 27.9 (34) 17.0 (104)   44.4 (103) 17.7 (200)   18.9 (1602)
 1–25 g/wk 17.2 (21) 26.2 (160)   18.5 (43) 23.2 (262)   19.3 (1643)
 25–50 g/wk 32.8 (40) 27.7 (169)   16.4 (38) 29.5 (333)   32.3 (2742)
  > 50 g/wk 21.3 (26) 27.9 (170)   20.7 (48) 29.5 (332)   28.5 (2508)
 Missing 0.8 (1) 1.1 (7)   2.1 (5) 2.9 (34)   10.0 (942)
Physical activity, % (n)    0.07    <  0.001  
  < 40 MET h/d 40.2 (47) 31.6 (188)   54.1 (120) 39.9 (443)   35.4 (2913)
 40–45 MET h/d 32.5 (38) 36.8 (219)   32.0 (71) 35.4 (393)   36.0 (2969)
 45–50 MET h/d 12.8 (15) 20.8 (124)   8.6 (19) 16.5 (183)   18.6 (1535)
  > 50 MET h/d 14.5 (17) 10.8 (64)   5.4 (12) 8.1 (90)   10.0 (822)
 Missing 4.1 (5) 2.5 (15)   6.3 (15) 4.5 (52)   12.7 (1198)
Smoking status, % (n)    0.38    0.17  
 Never 52.5 (64) 53.9 (327)   41.1 (97) 46.5 (536)   46.4 (3977)
 Former 32.0 (39) 34.9 (212)   44.5 (105) 42.6 (491)   41.7 (3568)
 Current 15.6 (19) 11.2 (68)   14.4 (34) 10.9 (125)   11.9 (1020)
 Missing 0.0 (0) 0.5 (3)   0.4 (1) 0.8 (9)   9.2 (872)
Statin therapy (current), % (n) 36.1 (44) 4.3 (26) <  0.001 61.2 (145) 11.5 (134) <  0.001 8.9 (839)
Low-dose aspirin (current), % (n) 15.6 (19) 2.1 (13) <  0.001 35.0 (83) 6.5 (76) <  0.001 5.1 (483)
Charlson comorbidity index, % (n)    <  0.001    <  0.001  
 0 82.0 (100) 97.0 (592)   73.8 (175) 92.2 (1070)   94.5 (8913)
 1 14.8 (18) 2.6 (16)   15.2 (36) 6.5 (75)   4.8 (452)
  ≥ 2 3.3 (4) 0.3 (2)   11.0 (26) 1.4 (16)   0.8 (72)
Benign breast disease, % (n)    0.77    0.78  
  No 78.1 (89) 76.8 (464)   75.8 (175) 74.9 (856)   76.8 (7084)
 Yes 21.9 (25) 23.2 (140)   24.2 (56) 25.1 (287)   23.2 (2145)
 Missing 6.6 (8) 1.0 (6)   2.5 (6) 1.6 (18)   2.2 (208)
Family history of breast cancer, % (n)    0.05    0.04  
 No 84.0 (100) 90.2 (534)   80.9 (182) 86.1 (963)   87.0 (7944)
 Yes 16.0 (19) 9.8 (58)   19.1 (43) 13.9 (155)   13.0 (1188)
 Missing 2.5 (3) 3.0 (18)   5.1 (12) 3.7 (43)   3.2 (305)
Age at diagnosis, years, mean (SD) 19.9 (7.6)   54.8 (8.2)  
Diabetes duration, years, mean (SD) 29.7 (10.2)   4.9 (2.5)  
Insulin therapy, % (n)        
 Glargine insulin 53.3 (65)   31.2 (74)  
 Nonglargine insulin 46.7 (57)   68.8 (163)  
Comedication metformin, % (n)        
 No 95.9 (117)   47.3 (112)  
 Yes 4.1 (5)   52.7 (125)  
  1. Abbreviations: T1D Type 1 diabetes, T2D Type 2 diabetes, BMI Body mass index, OC Oral contraceptive, HRT Hormone replacement therapy, MET Metabolic equivalent of activity level
  2. Study populations: matched cohort analysis including insulin-treated diabetes and insulin genetic score analysis including women with available genotyping data and no known diabetes. All women in the study population were free of cancer at study entry (i.e., the baseline screening visit). In total, 21 T2D patients could not be matched to a maximum of 5 individuals (i.e., 20 patients were matched to 4 individuals, and 1 patient was matched to 1 individual), leaving 610 and 1161 age-matched women without diabetes for insulin-treated T1D and T2D analyses, respectively. Participant characteristics were compared using t tests for continuous data and chi-squared tests for categorical variables