Is infertility really associated with higher levels of mental distress in the female population? Results from the North-Trøndelag Health Study and the Medical Birth Registry of Norway

Figures & data

Figure 1. Flow chart describing sampling procedure, i.e. number of women in HUNT 2 (Questionnaires 1 and 2) with valid information on predictor and outcome variables.

Table 1. Descriptive statistics of the total n = 12 584 sample and by subgroup according to fertility status.

	Mean (SD) range
	Current primary infertility n = 350	Current secondary infertility n = 265	Resolved infertility n = 1081	Voluntarily childfree n = 2318	Mothers without infertility n = 8570	Total n = 12 584
Age (years)	33.9 (6.95) 20–45	36.4 (5.60) 22–45	36.2 (5.50) 20–45	25.7 (6.00) 19–45	35.4 (6.41) 19–45	33.7 (7.33) 19–45
HADS anxiety subscale score	4.7 (3.42) 0–17	4.6 (3.59) 0–15	4.8 (3.45) 0–19	4.3 (3.21) 0–21	4.5 (3.40) 0–20	4.5 (3.37) 0–21
HADS depression subscale score	2.7 (2.73) 0–15	2.8 (2.61) 0–15	2.9 (2.88) 0–18	1.9 (2.36) 0–18	2.8 (2.75) 0–19	2.6 (2.71) 0–19
	n (%)
Score ≥ 8 on HADS anxiety subscale	69 (20)	47 (18)	204 (19)	339 (15)	1492 (17)	2151 (17)
Score ≥ 8 on HADS depression subscale	23 (7)	18 (7)	88 (8)	82 (4)	610 (7)	821 (7)
Education (years)
≤9  10–12  13–15  ≥16	50 (14) 193 (55) 65 (19) 38 (11)	47 (18) 161 (61) 35 (13) 22 (8)	137 (13) 662 (61) 184 (17) 93 (9)	99 (4) 1196 (52) 700 (30) 296 (13)	1299 (15) 4841 (56) 1589 (19) 789 (9)	1632 (13) 7053 (56) 2573 (21) 1238 (10)
Marital status
Married/registered partner  Unmarried  Divorced/separated  Widow	183 (52) 132 (38) 27 (8) 4 (1.1)	151 (57) 69 (26) 39 (15) 5 (2)	745 (69) 225 (21) 104 (10) 4 (0.4)	109 (5) 2162 (93) 20 (0.9) 1 (0.04)	5249 (61) 2516 (29) 731 (9) 56 (0.7)	6437 (51) 5104 (41) 921 (7) 70 (0.6)
Hypothyroidism	9 (2.6)	11 (4.2)	35 (3.2)	38 (1.6)	219 (2.6)	312 (2.5)
Body mass index
≤18.49  18.50–24.99  25.00–29.99  ≥30.00	2 (0.6) 183 (52) 107 (31) 55 (16)	2 (0.8) 125 (47) 99 (37) 39 (15)	15 (1.4) 555 (51) 332 (31) 178 (17)	47 (2.0) 1445 (62) 585 (25) 229 (10)	102 (1.2) 4726 (55) 2723 (32) 979 (11)	168 (1.3) 7034 (56) 3846 (31) 1480 (12)
Daily cigarette smoking	155 (44)	122 (46)	402 (37)	564 (24)	2954 (35)	4197 (33)
Use of alcohol (units per week)
None  1–9  ≥10	82 (23) 223 (64) 0 (0)	69 (26) 158 (60) 0 (0)	270 (25) 661 (61) 3 (0.3)	339 (15) 1658 (72) 12 (0.5)	2060 (24) 5231 (61) 15 (0.2)	2820 (22) 7931 (63) 30 (0.2)
Number of liveborn children*  0  1  2  3  4–9	350 (100) 0 (0) 0 (0) 0 (0) 0 (0)	0 (0) 177 (67) 74 (28) 11 (4) 3 (1.1)	0 (0) 261 (24) 514 (48) 268 (25) 38 (4)	2318 (100) 0 (0) 0 (0) 0 (0) 0 (0)	211 (2.5)† 1678 (20) 3973 (46) 2185 (26) 523 (6)	2879 (23) 2116 (17) 4561 (36) 2464 (20) 564 (4)

Missing values are not reported and therefore percentages do not always add up to 100.

*Information from the Medical Birth Registry of Norway (MBRN).

†Women with live-born children prior to the first registration in the MBRN or pregnant at the time of HUNT 2 are also included in the reference category of mothers without infertility.

Table 2. Linear regression model with infertility (ever) as independent variable and HADS-A or -D subscales as dependent variables; n = 12 584.

Model	HADS-A			HADS-D
	B	95% CI	p	B	95% CI	p
Unadjusted*	0.25	0.07 to 0.42	0.008	0.26	0.12 to 0.40	<0.001
Adjusted analyses
Parity†	0.26	0.08 to 0.43	0.006	0.30	0.16 to 0.44	<0.001
Infertility × parity	0.24	−0.05 to 0.53	0.338	0.19	−0.04 to 0.42	0.094
Age	0.24	0.06 to 0.41	0.005	0.13	−0.01 to 0.27	0.037
Education	0.21	0.04 to 0.38	0.021	0.23	0.09 to 0.37	<0.001
Marital status	0.22	0.05 to 0.40	0.010	0.18	0.04 to 0.32	0.006
Hypothyroidism	0.24	0.07 to 0.41	0.009	0.26	0.12 to 0.40	<0.001
Body mass index	0.25	0.07 to 0.42	0.007	0.24	0.10 to 0.38	<0.001
Cigarette smoking	0.17	−0.00 to 0.34	0.056	0.21	0.07 to 0.35	0.001
Use of alcohol	0.25	0.07 to 0.42	0.007	0.25	0.12 to 0.39	<0.001
Fully adjusted‡	0.28	−0.03 to 0.59	0.156	0.32	0.08 to 0.57	0.002

*Infertility alone explained 0.06 % (F(1,12582) = 7.74, p = 0.008) and 0.1% (F(1,12582) = 13.55, p ≤ 0.0011) of the variances of HADS-A and -D, respectively.

†Defined as number of live-born children registered in the MBRN.

‡The fully adjusted models explained 3% (F(18,12565) = 22.50, p ≤ 0.001) and 5% (F(18,12565) = 36.61, p ≤ 0.001) of the variances in HADS-A and -D, respectively.

Table 3. Linear regression model with subgroups of women categorized according to infertility or number of live-born children as independent variable and HADS-A and -D subscales as dependent variables; n = 12 584.

Model	Subgroup*	HADS-A			HADS-D
		B	95% CI	p	B	95% CI	p
Unadjusted†	Current primary infertility Current secondary infertility Resolved infertility Voluntarily childfree	0.14 0.04 0.27 −0.17	−0.22 to 0.50 −0.37 to 0.46 0.06 to 0.48 −0.33 to −0.02	0.432 0.942 0.005 0.492	−0.11 0.01 0.16 −0.84	−0.39 to 0.18 −0.33 to 0.34 −0.01 to 0.33 −0.96 to −0.71	0.397 0.747 0.063 <0.001
Fully adjusted‡	Current primary infertility Current secondary infertility Resolved infertility Voluntarily childfree	0.06 −0.12 0.25 −0.05	−0.30 to 0.42 −0.53 to 0.29 0.04 to 0.47 −0.23 to 0.14	0.764 0.479 0.006 0.625	−0.10 −0.16 0.12 −0.36	−0.39 to 0.18 −0.48 to 0.17 −0.05 to 0.28 −0.50 to −0.21	0.401 0.514 0.181 <0.001

*Subgroup mothers without previous or current infertility is reference category.

†Subgroups according to infertility type - or number of live-born children explained 0.01% (F(4,12579) = 3.43, p = 0.049) and 2% (F(4,12579) = 48.32, p < 0.001) of the variance in HADS-A and -D subscales, respectively.

‡The fully adjusted models explained 3% (F (19,12564) = 21.13, p < 0.001) and 5% (F (19,12564) = 34.66, p < 0.001), of the variance in HADS-A and -D subscales, respectively.