Self-reported psychological stress and the risk of breast cancer: A case-control study

Figures & data

Table I.  Selected characteristics of the study subjects by disease status.

	Cases (n = 858)	Controls (n = 1085)	P value^*
Characteristics	Number, %
Education level
Elementary school	262 (30.5)	253 (23.3)
Middle school	339 (39.5)	379 (34.9)
High school (academy, university)	257 (30.0)	453 (41.8)	< 0.0001
First-degree relative breast cancer	138 (16.1)	82 (7.6)	< 0.0001
Ever users of OCP	153 (17.8)	158 (14.6)	0.01
Ever users of HRT	301 (35.1)	371 (34.2)	0.68
Ever regular cigarette smoker	413 (48.2)	355 (32.8)	< 0.0001
Exposure to cigarette smoke	458 (55.7)	347 (32.6)	< 0.0001
	Mean (SD)
Age at entry (years)	55.3 (9.7)	54.8 (9.5)	0.24
BMI (kg/m^2)	26.2 (4.7)	25.3 (4.1)	0.0001
Age at menarche (years)	13.82 (1.61)	13.80 (1.57)	0.76
Parity	1.90 (1.10)	1.91 (1.03)	0.80
Age at first birth (years)	23.3 (3.94)	24.0 (3.95)	0.09
Age at menopause (years)	48.7 (5.3)	49.2 (4.65)	0.07
Breast-feeding (months)	6.6 (7.52)	10.8 (10.37)	< 0.0001
Alcohol drinking (drinks/week)^†	1.20 (0.87)	1.14 (0.95)	0.27
Lifetime recreational activity (h/wk/yr)	4.17 (6.34)	5.27 (4.59)	< 0.0001
Lifetime household activity (h/wk/yr)	16.6 (11.8)	19.4 (11.29)	< 0.0001
Lifetime occupational activity (h/wk/yr)	24.4 (10.09)	26.2 (12.81)	0.0026

SD, standard deviation

^* Student's t-test differences in means frequency distributions; COCP, oral contraceptive pills; HRT, hormonal replacement therapy

^† One alcoholic drink, tin of beer or a small bottle, 125 ml of wine or 30 g of high-grade alcohols. Values are mean (SD) or the percent of total reporting (%).

Table II.  Odds ratios and 95% confidence intervals for breast cancer by categories of self-reported major life events.

Life event (Holmes and Rahe weight)	Cases(N = 858, %)	Controls(N = 1085, %)	OR (95%CI)
			Age-adjusted	Multivariate^†	Multivariate^‡
Death of husband (100)^*	121(14.1)	134(12.3)	1.31(0.77–2.27)	1.42(0.76–2.70)	1.30(0.63–2.35)
Divorce (73) or separation (65)	102(11.9)	99(9.1)	1.35(1.01–1.82)	1.36(0.97–1.92)	1.68(0.80–1.63)
Death of a close family member (63)	382(44.2)	348(32.1)	2.56(1.87–3.51)	3.14(2.18–4.54)	2.48(1.70–3.64)
Personal injury or illness (53)	211(24.6)	144(13.3)	4.28(2.75–6.69)	3.95(2.39–6.55)	2.60(1.63–4.62)
Change in health of family member (44)	183(21.3)	168(15.5)	1.95(1.26–3.00)	2.46(1.49–4.04)	1.60(0.95–2.70)
Imprisonment, trouble with the law (29)	39(4.5)	19(1.8)	2.66(1.52–4.63)	3.74(1.99–7.03)	2.94(1.56–5.75)
Loss of a job (47)	84(9.8)	72(6.6)	2.52(1.29–4.80)	2.12(1.01–4.49)	1.72(0.72–3.39)
Retirement (45)	95(11.1)	62(5.7)	2.03(1.45–2.85)	2.13(1.44–3.15)	1.52(1.08–2.45)

OR, odds ratio; CI, 95% confidence interval

^* P for the case–control difference >0.05

^† Adjusted for age, lifetime recreational physical activity, place of residence, education, age at menarche, breast-feeding, family history of breast cancer, exposure to cigarette smoke, alcohol consumption, intake of vegetables and fruits

^‡ Adjusted as multivariate and further for the remaining items of life events. Values given in parentheses mean weight of an individual event on the Holmes and Rahe scale.

Table III.  Breast cancer odds ratios and 95% confidence intervals according to life change scores.

Period of life	Score range	Cases (N = 858)	Controls (N = 1085)	Age adjusted OR (95% CI)	Multivariable-adjusted OR (95%CI)^*
Lifetime
	0-70	410	673	1.00	1.00
	71-140	206	234	1.44(1.15–1.81)	1.56(1.20–2.02)
	141-210	141	136	1.68(1.28–2.19)	1.71(1.25–2.33)
	>210	101	42	3.88(2.65–5.70)	5.09(3.41–8.50)
P trend				P < 0.0001	P < 0.0001
Beginning at birth and ending 5 years before the cancer diagnosis
	0-70	529	798	1.00	1.00
	71-140	177	195	1.37(1.08–1.73)	1.33(1.03–1.72)
	141-210	98	73	2.01(1.45–2.79)	2.03(1.41–2.91)
	>210	54	19	4.26(2.48–7.31)	5.07(2.80–9.18)
P trend				P < 0.0001	P < 0.0001

OR, odds ratio; CI, 95% confidence interval

^* Adjusted for age, lifetime recreational physical activity, place of residence, education, age at menarche, breast-feeding, sleeping time, family history of breast cancer, fruit consumption, alcohol consumption, and exposure to cigarette smoke. P trend: a test for linear trend calculated from logistic regression by modeling the number of life change scores as the continuous variable.

Table IV.  Breast cancer odds ratios and 95% confidence intervals according to number of major stressful lifetime life events.

Total number of major life events	Cases (N = 858)	Controls (N = 1085)	Age adjusted OR (95% CI)	Multivariable-adjusted OR^*
Not reporting major life events	156	395	1.00	1.00
1–3 major life events	585	633	2.33 (1.88–2.90)	2.58 (2.0–3.34)
4–6 major life events	103	54	4.69 (3.21–6.87)	5.33 (4.01–8.21)
7–9 major life events	14	3	–	–

OR, odds ratio; CI, 95% confidence interval; P trend < 0.0001

^* Adjusted for total recreational physical activity, place of residence, education, age at menarche, breast-feeding, sleeping time, family history of breast cancer, vitamin, fruit consumption, and alcohol intake. Nine life events were identified as major on the basis of the life event weights as follows: the death of a husband, divorce, separation, the death of a close relative or friend, personal injury or illness, change in health of family member, imprisonment/trouble with the law, loss of job, and retirement. P trend: a test for linear trend calculated from logistic regression by modeling the number of major life events as the continuous variable.