Baseline (1993-1998) characteristics of participants in the WHIOS by region of residence at baseline among women included in the analysis of breast cancer incidence and geographic region of residence (n = 71,662)
| . | Southern . | Middle . | Northern . | P . |
|---|---|---|---|---|
| . | n (%) . | n (%) . | n (%) . | . |
| Age at baseline, y | <0.001 | |||
| 50-59 | 8,779 (35) | 4,795 (35) | 10,074 (31) | |
| 60-69 | 10,816 (43) | 5,825 (42) | 15,084 (47) | |
| 70-79 | 5,759 (23) | 3,275 (24) | 7,255 (22) | |
| Race/ethnicity | <0.001 | |||
| Caucasian | 19,611 (77) | 11,787 (85) | 29,378 (91) | |
| African American | 1,908 (8) | 1,172 (8) | 1,989 (6) | |
| Hispanic | 1,731 (7) | 271 (2) | 421 (1) | |
| American Indian | 162 (0.6) | 47 (0.3) | 69 (0.2) | |
| Asian/Pacific Islander | 1,555 (6) | 385 (3) | 216 (0.7) | |
| Unknown | 387 (2) | 233 (2) | 340 (1) | |
| Education | <0.001 | |||
| 0-8 y | 533 (2) | 84 (0.6) | 291 (0.9) | |
| Some high school | 867 (3) | 326 (2) | 1,001 (3) | |
| High school diploma/GED | 3,705 (15) | 1,652 (12) | 6,115 (19) | |
| School after high school | 9,938 (37) | 4,889 (35) | 11,152 (34) | |
| College degree or higher | 10,311 (41) | 6,944 (50) | 13,854 (43) | |
| Family history of breast cancer | <0.001 | |||
| Yes | 4,342 (17) | 2,540 (18) | 6,021 (19) | |
| No | 19,922 (79) | 10,726 (77) | 25,072 (77) | |
| Missing | 1,090 (4) | 629 (5) | 1,320 (4) | |
| Age at menarche, y | 0.004 | |||
| ≤11 | 5,501 (22) | 3,069 (22) | 7,215 (22) | |
| 12-13 | 13,946 (55) | 7,806 (56) | 17,948 (55) | |
| ≥14 | 5,907 (23) | 3,020 (22) | 7,250 (22) | |
| Age at menopause, y | <0.001 | |||
| 20-29 | 258 (1) | 102 (0.7) | 144 (0.4) | |
| 30-39 | 2,348 (9) | 1,071 (8) | 2,157 (7) | |
| 40-49 | 10,525 (42) | 5,368 (39) | 11,957 (37) | |
| 50-60 | 12,223 (48) | 7,354 (53) | 18,155 (56) | |
| Age at first birth, y | <0.001 | |||
| Never pregnant | 2,383 (9) | 1,432 (10) | 3,281 (10) | |
| No term pregnancy | 770 (3) | 445 (3) | 701 (2) | |
| <20 | 3,439 (14) | 1,480 (11) | 2,949 (9) | |
| 20-24 | 11,360 (45) | 5,831 (42) | 15,053 (46) | |
| 25-29 | 5,623 (22) | 3,449 (25) | 7,941 (25) | |
| 30-34 | 1,358 (5) | 945 (7) | 1,918 (6) | |
| 35-39 | 3,56 (1) | 269 (2) | 478 (1) | |
| 40-44 | 60 (0.2) | 41 (0.3) | 88 (0.3) | |
| 45+ | 5 (0.02) | 3 (0.02) | 4 (0.01) | |
| No of term pregnancies | <0.001 | |||
| Never pregnant | 2,383 (9) | 1,432 (10) | 3,281 (10) | |
| Never had term pregnancy | 770 (3) | 445 (3) | 701 (2) | |
| 1 | 2,510 (10) | 1,386 (10) | 2,495 (8) | |
| 2 | 7,246 (29) | 3,825 (28) | 7,993 (25) | |
| 3 | 6,137 (24) | 3,309 (24) | 7,993 (25) | |
| 4 | 3,549 (14) | 1,924 (14) | 4,965 (15) | |
| 5+ | 2,759 (11) | 1,574 (11) | 4,985 (15) | |
| Weight quintiles, kg | <0.001 | |||
| Quintile 1: <58.7 | 5,647 (22) | 2,786 (20) | 5,870 (18) | |
| Quintile 2: ≥58.7 to <65.0 | 5,279 (21) | 2,860 (21) | 6,405 (20) | |
| Quintile 3: ≥ 65.0 to <71.8 | 4,926 (19) | 2,747 (20) | 6,511 (20) | |
| Quintile 4: ≥71.8 to <81.9 | 4,776 (19) | 2,725 (20) | 6,742 (21) | |
| Quintile 5: ≥81.9 | 4,726 (19) | 2,777 (20) | 6,885 (21) | |
| Body mass index, kg/m2* | <0.001 | |||
| Underweight (<18.5) | 377 (2) | 166 (1) | 302 (0.9) | |
| Normal (≥18.5 to 24.9) | 10,843 (43) | 5,884 (43) | 12,155 (38) | |
| Overweight (25.0-29.9) | 8,369 (33) | 4,549 (33) | 11,361 (35) | |
| Obesity I (30.0-34.9) | 3,571 (14) | 2,014 (15) | 5,277 (16) | |
| Obesity II (35.0-39.9) | 1,247 (5) | 722 (5) | 2,023 (6) | |
| Extreme obesity III (≥40) | 785 (3) | 446 (3) | 1,106 (3) | |
| Recreational Physical activity quintiles, MET h/wk | <0.001 | |||
| Quintile 1: <2.0 | 5,519 (22) | 2,432 (18) | 6,491 (20) | |
| Quintile 2: ≥2.0 to < 7.2 | 4,859 (19) | 2,635 (19) | 6,595 (20) | |
| Quintile 3: ≥7.2 to < 13.5 | 5,082 (20) | 2,873 (21) | 6,764 (21) | |
| Quintile 4: ≥13.5 to <23.3 | 4,823 (19) | 2,941 (21) | 6,525 (20) | |
| Quintile 5: ≥23.3 | 5,071 (20) | 3,014 (22) | 6,038 (19) | |
| Hormone therapy duration of use, y | <0.001 | |||
| None | 7,278 (29) | 4,242 (31) | 14,714 (45) | |
| <5 | 5,872 (23) | 3,394 (24) | 7,100 (22) | |
| 5 to <10 | 4,089 (16) | 2,204 (16) | 4,160 (13) | |
| 10+ | 8,115 (32) | 4,055 (29) | 6,439 (20) | |
| Alcohol intake | <0.001 | |||
| Nondrinker | 4,084 (16) | 1,145 (8) | 2,407 (7) | |
| Past drinker | 4,897 (19) | 2,427 (17) | 5,483 (17) | |
| <1 drink per month | 2,717 (11) | 1,503 (11) | 4,092 (13) | |
| <1 drink per week | 4,615 (18) | 2,827 (20) | 7,035 (22) | |
| 1 to <7 drinks per week | 5,886 (23) | 3,829 (28) | 9,303 (29) | |
| 7+ drinks per week | 3,155 (12) | 2,164 (16) | 4,093 (13) | |
| Vitamin D intake from foods quintiles, energy adjusted IU/d | <0.001 | |||
| Quintile 1: <88.0 | 5,708 (23) | 2,917 (21) | 5,707 (18) | |
| Quintile 2: ≥88.0 to <123.7 | 5,386 (21) | 2,848 (21) | 6,099 (19) | |
| Quintile 3: ≥123.7 to <163.9 | 5,191 (20) | 2,774 (20) | 6,367 (20) | |
| Quintile 4: ≥163.9 to <227.7 | 4,776 (19) | 2,740 (20) | 6,817 (21) | |
| Quintile 5: ≥227.7 | 4,293 (17) | 2,616 (19) | 7,423 (23) | |
| Vitamin D intake from foods and supplements quintiles, energy adjusted IU/d | <0.001 | |||
| Quintile 1: <123.4 | 5,765 (23) | 2,798 (20) | 5,769 (18) | |
| Quintile 2: ≥123.4 to <222.7 | 5,094 (20) | 2,704 (19) | 6,535 (20) | |
| Quintile 3: ≥222.7 to <450.6 | 4,574 (18) | 2,864 (21) | 6,894 (21) | |
| Quintile 4: ≥450.6 to <622.8 | 4,864 (19) | 2,841 (20) | 6,628 (20) | |
| Quintile 5: ≥622.8 | 5,057 (20) | 2,688 (19) | 6,587 (20) |
| . | Southern . | Middle . | Northern . | P . |
|---|---|---|---|---|
| . | n (%) . | n (%) . | n (%) . | . |
| Age at baseline, y | <0.001 | |||
| 50-59 | 8,779 (35) | 4,795 (35) | 10,074 (31) | |
| 60-69 | 10,816 (43) | 5,825 (42) | 15,084 (47) | |
| 70-79 | 5,759 (23) | 3,275 (24) | 7,255 (22) | |
| Race/ethnicity | <0.001 | |||
| Caucasian | 19,611 (77) | 11,787 (85) | 29,378 (91) | |
| African American | 1,908 (8) | 1,172 (8) | 1,989 (6) | |
| Hispanic | 1,731 (7) | 271 (2) | 421 (1) | |
| American Indian | 162 (0.6) | 47 (0.3) | 69 (0.2) | |
| Asian/Pacific Islander | 1,555 (6) | 385 (3) | 216 (0.7) | |
| Unknown | 387 (2) | 233 (2) | 340 (1) | |
| Education | <0.001 | |||
| 0-8 y | 533 (2) | 84 (0.6) | 291 (0.9) | |
| Some high school | 867 (3) | 326 (2) | 1,001 (3) | |
| High school diploma/GED | 3,705 (15) | 1,652 (12) | 6,115 (19) | |
| School after high school | 9,938 (37) | 4,889 (35) | 11,152 (34) | |
| College degree or higher | 10,311 (41) | 6,944 (50) | 13,854 (43) | |
| Family history of breast cancer | <0.001 | |||
| Yes | 4,342 (17) | 2,540 (18) | 6,021 (19) | |
| No | 19,922 (79) | 10,726 (77) | 25,072 (77) | |
| Missing | 1,090 (4) | 629 (5) | 1,320 (4) | |
| Age at menarche, y | 0.004 | |||
| ≤11 | 5,501 (22) | 3,069 (22) | 7,215 (22) | |
| 12-13 | 13,946 (55) | 7,806 (56) | 17,948 (55) | |
| ≥14 | 5,907 (23) | 3,020 (22) | 7,250 (22) | |
| Age at menopause, y | <0.001 | |||
| 20-29 | 258 (1) | 102 (0.7) | 144 (0.4) | |
| 30-39 | 2,348 (9) | 1,071 (8) | 2,157 (7) | |
| 40-49 | 10,525 (42) | 5,368 (39) | 11,957 (37) | |
| 50-60 | 12,223 (48) | 7,354 (53) | 18,155 (56) | |
| Age at first birth, y | <0.001 | |||
| Never pregnant | 2,383 (9) | 1,432 (10) | 3,281 (10) | |
| No term pregnancy | 770 (3) | 445 (3) | 701 (2) | |
| <20 | 3,439 (14) | 1,480 (11) | 2,949 (9) | |
| 20-24 | 11,360 (45) | 5,831 (42) | 15,053 (46) | |
| 25-29 | 5,623 (22) | 3,449 (25) | 7,941 (25) | |
| 30-34 | 1,358 (5) | 945 (7) | 1,918 (6) | |
| 35-39 | 3,56 (1) | 269 (2) | 478 (1) | |
| 40-44 | 60 (0.2) | 41 (0.3) | 88 (0.3) | |
| 45+ | 5 (0.02) | 3 (0.02) | 4 (0.01) | |
| No of term pregnancies | <0.001 | |||
| Never pregnant | 2,383 (9) | 1,432 (10) | 3,281 (10) | |
| Never had term pregnancy | 770 (3) | 445 (3) | 701 (2) | |
| 1 | 2,510 (10) | 1,386 (10) | 2,495 (8) | |
| 2 | 7,246 (29) | 3,825 (28) | 7,993 (25) | |
| 3 | 6,137 (24) | 3,309 (24) | 7,993 (25) | |
| 4 | 3,549 (14) | 1,924 (14) | 4,965 (15) | |
| 5+ | 2,759 (11) | 1,574 (11) | 4,985 (15) | |
| Weight quintiles, kg | <0.001 | |||
| Quintile 1: <58.7 | 5,647 (22) | 2,786 (20) | 5,870 (18) | |
| Quintile 2: ≥58.7 to <65.0 | 5,279 (21) | 2,860 (21) | 6,405 (20) | |
| Quintile 3: ≥ 65.0 to <71.8 | 4,926 (19) | 2,747 (20) | 6,511 (20) | |
| Quintile 4: ≥71.8 to <81.9 | 4,776 (19) | 2,725 (20) | 6,742 (21) | |
| Quintile 5: ≥81.9 | 4,726 (19) | 2,777 (20) | 6,885 (21) | |
| Body mass index, kg/m2* | <0.001 | |||
| Underweight (<18.5) | 377 (2) | 166 (1) | 302 (0.9) | |
| Normal (≥18.5 to 24.9) | 10,843 (43) | 5,884 (43) | 12,155 (38) | |
| Overweight (25.0-29.9) | 8,369 (33) | 4,549 (33) | 11,361 (35) | |
| Obesity I (30.0-34.9) | 3,571 (14) | 2,014 (15) | 5,277 (16) | |
| Obesity II (35.0-39.9) | 1,247 (5) | 722 (5) | 2,023 (6) | |
| Extreme obesity III (≥40) | 785 (3) | 446 (3) | 1,106 (3) | |
| Recreational Physical activity quintiles, MET h/wk | <0.001 | |||
| Quintile 1: <2.0 | 5,519 (22) | 2,432 (18) | 6,491 (20) | |
| Quintile 2: ≥2.0 to < 7.2 | 4,859 (19) | 2,635 (19) | 6,595 (20) | |
| Quintile 3: ≥7.2 to < 13.5 | 5,082 (20) | 2,873 (21) | 6,764 (21) | |
| Quintile 4: ≥13.5 to <23.3 | 4,823 (19) | 2,941 (21) | 6,525 (20) | |
| Quintile 5: ≥23.3 | 5,071 (20) | 3,014 (22) | 6,038 (19) | |
| Hormone therapy duration of use, y | <0.001 | |||
| None | 7,278 (29) | 4,242 (31) | 14,714 (45) | |
| <5 | 5,872 (23) | 3,394 (24) | 7,100 (22) | |
| 5 to <10 | 4,089 (16) | 2,204 (16) | 4,160 (13) | |
| 10+ | 8,115 (32) | 4,055 (29) | 6,439 (20) | |
| Alcohol intake | <0.001 | |||
| Nondrinker | 4,084 (16) | 1,145 (8) | 2,407 (7) | |
| Past drinker | 4,897 (19) | 2,427 (17) | 5,483 (17) | |
| <1 drink per month | 2,717 (11) | 1,503 (11) | 4,092 (13) | |
| <1 drink per week | 4,615 (18) | 2,827 (20) | 7,035 (22) | |
| 1 to <7 drinks per week | 5,886 (23) | 3,829 (28) | 9,303 (29) | |
| 7+ drinks per week | 3,155 (12) | 2,164 (16) | 4,093 (13) | |
| Vitamin D intake from foods quintiles, energy adjusted IU/d | <0.001 | |||
| Quintile 1: <88.0 | 5,708 (23) | 2,917 (21) | 5,707 (18) | |
| Quintile 2: ≥88.0 to <123.7 | 5,386 (21) | 2,848 (21) | 6,099 (19) | |
| Quintile 3: ≥123.7 to <163.9 | 5,191 (20) | 2,774 (20) | 6,367 (20) | |
| Quintile 4: ≥163.9 to <227.7 | 4,776 (19) | 2,740 (20) | 6,817 (21) | |
| Quintile 5: ≥227.7 | 4,293 (17) | 2,616 (19) | 7,423 (23) | |
| Vitamin D intake from foods and supplements quintiles, energy adjusted IU/d | <0.001 | |||
| Quintile 1: <123.4 | 5,765 (23) | 2,798 (20) | 5,769 (18) | |
| Quintile 2: ≥123.4 to <222.7 | 5,094 (20) | 2,704 (19) | 6,535 (20) | |
| Quintile 3: ≥222.7 to <450.6 | 4,574 (18) | 2,864 (21) | 6,894 (21) | |
| Quintile 4: ≥450.6 to <622.8 | 4,864 (19) | 2,841 (20) | 6,628 (20) | |
| Quintile 5: ≥622.8 | 5,057 (20) | 2,688 (19) | 6,587 (20) |
NOTE: P value from a χ2 test comparing baseline characteristics by region of residence at baseline.
There is missing data for these variables, resulting in ns that do not add up to 71,662. Missing persons were not included in χ.