Genetic polymorphism in the manganese superoxide dismutase gene, antioxidant intake, and breast cancer risk: results from the Shanghai Breast Cancer Study

Table 1 Comparisons of cases and controls by selected demographic characteristics and major risk factors in the Shanghai Breast Cancer Study

Characteristic	Cases (n = 1125)	Controls (n = 1197)	P-value^a
Demographic factors
Age (years [mean ± SD])	47.63 ± 8.00	47.20 ± 8.78	0.217
Education, lower than middle school (%)	12.27	14.79	0.124
Major risk factors
Breast cancer in first-degree relatives (%)	3.38	2.26	0.101
Ever had breast fibroadenoma (%)	9.78	5.26	< 0.001
Age at menarche (years [mean ± SD])	14.41 ± 1.64	14.71 ± 1.73	0.004
Age at first live birth^b (years [mean ± SD])	26.82 ± 4.07	26.17 ± 3.83	< 0.001
Age at menopause^c (years [mean ± SD])	48.17 ± 4.65	47.46 ± 4.95	0.036
Physically active in past 10 years (%)	19.40	26.00	< 0.001
Body mass index (mean ± SD)	23.54 ± 3.39	23.25 ± 3.45	0.047
Waist-to-hip ratio (mean ± SD)	0.81 ± 0.06	0.80 ± 0.06	0.004

^aFrom χ² test (categorical variables) or T test (continuous variables). ^bAmong parous women.
^cAmong postmenopausal women. SD, standard deviation.

ISSN: 1465-542X