Food Sci Clin Nutr

Food Sciences and Clinical Nutrition, ISSN NoIssnPrint print, 0000-0000 online, Open Access

Article copyright, the authors; Journal compilation copyright, Food Sci Clin Nutr and Elmer Press Inc

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Original Article

Volume 1, 2026, e6

Age- and Time-Related Changes in Serum Ferritin Levels in Danish Women: A Population-Based Longitudinal Study of 1,174 Women Over a 10-Year Period: Influence of Nutritional Factors

↓ Figure 1. Selection of the female participants in the longitudinal study of serum ferritin in the three MONICA surveys.

↓ **Table 1.** Measurements of Blood Hemoglobin in All Women in the MONICA Cohort
	MONICA 1 (n = 1,172) 30–60 years, median 40 years	MONICA 10 (n = 969) 40–70 years, median 50 years	Wilcoxon test paired samples
The women were examined in MONICA 1, and 969 of them in MONICA 10 as well. *Values above and below the reference interval for Danish women; Wilcoxon test paired samples compare values in women examined in both surveys. IQR: interquartile range; SD: standard deviation.
Hemoglobin, g/L			P < 0.001, n = 968
Mean ± SD	139 ± 10.3	137 ± 9.5
Median (IQR)	139 (132–143)	137 (132–143)
			Fisher’s exact test
Hemoglobin > 153 g/L*, n (%)	55 (4.7%)	19 (2.0%)	P = 0.0005
Hemoglobin < 120 g/L*, n (%)	31 ( 2.6%)	25 (2.5%)	P = 0.6
Hemoglobin < 120 g/L and
Ferritin < 30 µg/L, n (%)	16 (1.4%)	8 (0.8%)	P = 0.2
Ferritin < 15 µg/L, n (%)	14 (1.2%)	25 (0.3%)	P = 0.026

↓ Table 1. Measurements of Blood Hemoglobin in All Women in the MONICA Cohort

MONICA 1 (n = 1,172)
30–60 years, median 40 years

MONICA 10 (n = 969)
40–70 years, median 50 years

Wilcoxon test paired samples

The women were examined in MONICA 1, and 969 of them in MONICA 10 as well. *Values above and below the reference interval for Danish women; Wilcoxon test paired samples compare values in women examined in both surveys. IQR: interquartile range; SD: standard deviation.

Hemoglobin, g/L

P < 0.001, n = 968

Mean ± SD

139 ± 10.3

137 ± 9.5

Median (IQR)

139 (132–143)

137 (132–143)

Fisher’s exact test

Hemoglobin > 153 g/L*, n (%)

55 (4.7%)

19 (2.0%)

P = 0.0005

Hemoglobin < 120 g/L*, n (%)

31 ( 2.6%)

25 (2.5%)

P = 0.6

Hemoglobin < 120 g/L and

Ferritin < 30 µg/L, n (%)

16 (1.4%)

8 (0.8%)

P = 0.2

Ferritin < 15 µg/L, n (%)

14 (1.2%)

25 (0.3%)

P = 0.026

↓ **Table 2.** Longitudinal Measurements of Serum Ferritin in All Women in the MONICA Cohort
	MONICA 1 (n = 1,174) 30–60 years, median 40 years	MONICA 5 (n = 1,057) 35–65 years, median 45 years	MONICA 10 (n = 968) 40–70 years, median 50 years	Wilcoxon test paired samples	Friedman test paired samples
The women were invited for examination three times. All were examined in MONICA 1, and the majority subsequently in MONICA 5 and/or MONICA 10, i.e., all had at least two measurements of ferritin. Friedman test compares values in women examined in all three surveys. IQR: interquartile range.
Ferritin, µg/L, median (IQR)	48 (26–83)	59 (36–98)	66 (36–121)	1 vs. 5, P < 0.0001, n = 1,057 5 vs. 10, P < 0.0001, n = 851	P < 0.00001, n = 851
Geometric mean	44	60	65	Chi-square test
Ferritin > 200 µg/L	38 (3.2%)	46 (4.4%)	83 (8.6%)	P < 0.0001
Ferritin < 30 µg/L	351 (29.9%)	187 (17.7%)	185 (19.1%)	P < 0.0001
Ferritin < 15 µg/L	146 (12.4%)	27 (2.6%)	48 (5.0%)	P < 0.0001
Menopausal	447 (38.1%)		548 (56.6%)	P < 0.0001

↓ Table 2. Longitudinal Measurements of Serum Ferritin in All Women in the MONICA Cohort

MONICA 1 (n = 1,174)
30–60 years, median 40 years

MONICA 5 (n = 1,057)
35–65 years, median 45 years

MONICA 10 (n = 968)
40–70 years, median 50 years

Wilcoxon test paired samples

Friedman test paired samples

The women were invited for examination three times. All were examined in MONICA 1, and the majority subsequently in MONICA 5 and/or MONICA 10, i.e., all had at least two measurements of ferritin. Friedman test compares values in women examined in all three surveys. IQR: interquartile range.

Ferritin, µg/L, median (IQR)

48 (26–83)

59 (36–98)

66 (36–121)

1 vs. 5, P < 0.0001, n = 1,057
5 vs. 10, P < 0.0001, n = 851

P < 0.00001, n = 851

Geometric mean

Chi-square test

Ferritin > 200 µg/L

38 (3.2%)

46 (4.4%)

83 (8.6%)

P < 0.0001

Ferritin < 30 µg/L

351 (29.9%)

187 (17.7%)

185 (19.1%)

P < 0.0001

Ferritin < 15 µg/L

146 (12.4%)

27 (2.6%)

48 (5.0%)

P < 0.0001

Menopausal

447 (38.1%)

548 (56.6%)

P < 0.0001

↓ **Table 3.** The Number of Blood Donors in Women According to Age in MONICA 1 and MONICA 10 Surveys
Age, years	MONICA 1	Age, years	MONICA 10	Fisher’s exact test
30	46/319 (14.4%)	40	42/275 (15.3%)	P = 0.3
40	54/319 (16.9%)	50	26/269 (9.7%)	P = 0.002
50	37/286 (12.9%)	60	15/237 (6.3%)	P < 0.0001
60	22/250 (8.8%)	70	1/188 (0.5%)	P < 0.0001
30–60	159/1,174 (13.5%)	40–70	84/969 (8.7%)	P < 0.0001

↓ Table 3. The Number of Blood Donors in Women According to Age in MONICA 1 and MONICA 10 Surveys

Age, years

MONICA 1

Age, years

MONICA 10

Fisher’s exact test

46/319 (14.4%)

42/275 (15.3%)

P = 0.3

54/319 (16.9%)

26/269 (9.7%)

P = 0.002

37/286 (12.9%)

15/237 (6.3%)

P < 0.0001

22/250 (8.8%)

1/188 (0.5%)

P < 0.0001

30–60

159/1,174 (13.5%)

40–70

84/969 (8.7%)

P < 0.0001

↓ **Table 4.** Longitudinal Measurements of Serum Ferritin in Women, Blood Donors, in the MONICA Cohort
	MONICA 1 (n = 159)	MONICA 5 (n = 140)	MONICA 10 (n = 166)	Wilcoxon test paired samples	Friedman test paired samples
The women were invited for examination three times. All were examined in MONICA 1, and the majority subsequently in MONICA 5 and/or MONICA 10, i.e., all had at least two measurements of ferritin. Friedman test compares values in women examined in all three surveys. *Compared with ferritin levels in non-blood-donors in Table 5, Mann–Whitney test, P < 0.0001. IQR: interquartile range.
Ferritin, µg/L, median (IQR)	36 (14–56)*	41 (27–73)*	39 (22–77)*	1 vs. 5, P < 0.0001, n = 140 5 vs. 10, P = 0.0001, n = 120	P < 0.00001, n = 120
Geometric mean	31	44	41	Chi-square test
Ferritin > 200 µg/L	6 (3.8%)	5 (3.6%)	7 (4.2%)	P = 0.5
Ferritin < 30 µg/L	64 (40.3%)	44 (31.4%)	66 (39.8%)	P = 0.001
Ferritin < 15 µg/L	40 (25.2%)	4 (2.9%)	17 (10.2%)	P = 0.001
Menopausal	44 (27.7%)		73 (44.0%)	P = 0.0001

↓ Table 4. Longitudinal Measurements of Serum Ferritin in Women, Blood Donors, in the MONICA Cohort

MONICA 1 (n = 159)

MONICA 5 (n = 140)

MONICA 10 (n = 166)

Wilcoxon test paired samples

Friedman test paired samples

Ferritin, µg/L, median (IQR)

36 (14–56)*

41 (27–73)*

39 (22–77)*

1 vs. 5, P < 0.0001, n = 140
5 vs. 10, P = 0.0001, n = 120

P < 0.00001, n = 120

Geometric mean

Chi-square test

Ferritin > 200 µg/L

6 (3.8%)

5 (3.6%)

7 (4.2%)

P = 0.5

Ferritin < 30 µg/L

64 (40.3%)

44 (31.4%)

66 (39.8%)

P = 0.001

Ferritin < 15 µg/L

40 (25.2%)

4 (2.9%)

17 (10.2%)

P = 0.001

Menopausal

44 (27.7%)

73 (44.0%)

P = 0.0001

↓ **Table 5.** Longitudinal Measurements of Serum Ferritin in Women, Non-Blood-Donors, in the MONICA Cohort
	MONICA 1 (n = 1,015)	MONICA 5 (n = 917)	MONICA 10 (n = 811)	Wilcoxon test paired samples	Friedman test paired samples
The women were invited for examination three times. All were examined in MONICA 1, and the majority subsequently examined in MONICA 5 and/or MONICA 10, i.e., all had at least two measurements of ferritin. Friedman test compares values in women examined in all three surveys. *Compared with ferritin levels in blood donors in Table 4, Mann–Whitney test, P < 0.0001. IQR: interquartile range.
Ferritin, µg/L, median (IQR)	52 (27–86)*	63 (38–102)*	73 (39–125)*	1 vs. 5, P < 0.0001, n = 917 5 vs. 10, P < 0.0001, n = 715	P < 0.00001, n = 715
Geometric mean	46	62	70	Chi-square test
Ferritin > 200 µg/L	32 (3.2%)	41 (4.5%)	76 (9.4%)	P < 0.0001
Ferritin < 30 µg/L	287 (28.3%)	142 (15.5%)	124 (15.3%)	P = 0.001
Ferritin < 15 µg/L	106 (10.4%)	23 (2.5%)	32 (3.9%)	P = 0.0001
Menopausal	403 (39.7%)		470 (58.0%)	P < 0.0001

↓ Table 5. Longitudinal Measurements of Serum Ferritin in Women, Non-Blood-Donors, in the MONICA Cohort

MONICA 1 (n = 1,015)

MONICA 5 (n = 917)

MONICA 10 (n = 811)

Wilcoxon test paired samples

Friedman test paired samples

The women were invited for examination three times. All were examined in MONICA 1, and the majority subsequently examined in MONICA 5 and/or MONICA 10, i.e., all had at least two measurements of ferritin. Friedman test compares values in women examined in all three surveys. *Compared with ferritin levels in blood donors in Table 4, Mann–Whitney test, P < 0.0001. IQR: interquartile range.

Ferritin, µg/L, median (IQR)

52 (27–86)*

63 (38–102)*

73 (39–125)*

1 vs. 5, P < 0.0001, n = 917
5 vs. 10, P < 0.0001, n = 715

P < 0.00001, n = 715

Geometric mean

Chi-square test

Ferritin > 200 µg/L

32 (3.2%)

41 (4.5%)

76 (9.4%)

P < 0.0001

Ferritin < 30 µg/L

287 (28.3%)

142 (15.5%)

124 (15.3%)

P = 0.001

Ferritin < 15 µg/L

106 (10.4%)

23 (2.5%)

32 (3.9%)

P = 0.0001

Menopausal

403 (39.7%)

470 (58.0%)

P < 0.0001

↓ **Table 6.** Longitudinal Measurements of Serum Ferritin in Women, Non-Blood-Donors, in the MONICA Cohort, Arranged According to Age at Inclusion in MONICA 1
	MONICA 1	MONICA 5	MONICA 10	Wilcoxon test paired samples	Friedman test paired samples
The women were invited for examination three times. All were examined in MONICA 1, and the majority subsequently in MONICA 5 and/or MONICA 10, i.e., all had at least two measurements of ferritin. Friedman test compares values in women examined in all three surveys. IQR: interquartile range.
Ferritin, µg/L, median (IQR)	36 (23–66), n = 273	46 (30–68), n = 258	41 (25–74), n = 215	1 vs. 5, P < 0.0001, n = 258 5 vs. 10, P = 0.5, n = 215 1 vs. 10, P = 0.009, n = 215	P < 0.00001, n = 218
Age, years	30	35	40
Menopausal	1.7%		4.6%
Ferritin, µg/L, median (IQR)	39 (21–69), n = 265	48 (29–78), n = 251	64 (37–110), n = 221	1 vs. 5, p < 0.0001, n = 251 5 vs. 10, p < 0.0001, n = 207	P < 0.00001, n = 207
Age, years	40	45	50
Menopausal	6.7%		64.3%
Ferritin, µg/L, median (IQR)	54 (30–84), n = 249	82 (52–120), n = 209	98 (56–157), n = 203	1 vs. 5, P < 0.0001, n = 209 5 vs. 10, P < 0.0001, n = 163	P < 0.00001, n = 163
Age, years	50	55	60
Menopausal	62.1%		97.4%
Ferritin, µg/L, median (IQR)	88 (50–136), n = 228	103 (65–146), n = 199	98 (61–151), n = 172	1 vs. 5, P = 0.0001, n =199 5 vs. 10, P = 0.2, n = 143 1 vs. 10, P = 0.0003, n = 172	P = 0.002, n = 143
Age, years	60	65	70
Menopausal	98.5%		100%
Mann–Whitney test	30 vs. 40, P = 0.4 40 vs. 50, P = 0.0004 50 vs. 60, P < 0.0001	35 vs. 45, P = 0.4 45 vs. 55, P < 0.0001 55 vs. 65, P = 0.004	40 vs. 50, P < 0.0001 50 vs. 60, P < 0.0001 60 vs. 70, P = 0.8

↓ Table 6. Longitudinal Measurements of Serum Ferritin in Women, Non-Blood-Donors, in the MONICA Cohort, Arranged According to Age at Inclusion in MONICA 1

MONICA 1

MONICA 5

MONICA 10

Wilcoxon test paired samples

Friedman test paired samples

Ferritin, µg/L, median (IQR)

36 (23–66), n = 273

46 (30–68), n = 258

41 (25–74), n = 215

1 vs. 5, P < 0.0001, n = 258
5 vs. 10, P = 0.5, n = 215
1 vs. 10, P = 0.009, n = 215

P < 0.00001, n = 218

Age, years

Menopausal

1.7%

4.6%

Ferritin, µg/L, median (IQR)

39 (21–69), n = 265

48 (29–78), n = 251

64 (37–110), n = 221

1 vs. 5, p < 0.0001, n = 251
5 vs. 10, p < 0.0001, n = 207

P < 0.00001, n = 207

Age, years

Menopausal

6.7%

64.3%

Ferritin, µg/L, median (IQR)

54 (30–84), n = 249

82 (52–120), n = 209

98 (56–157), n = 203

1 vs. 5, P < 0.0001, n = 209
5 vs. 10, P < 0.0001, n = 163

P < 0.00001, n = 163

Age, years

Menopausal

62.1%

97.4%

Ferritin, µg/L, median (IQR)

88 (50–136), n = 228

103 (65–146), n = 199

98 (61–151), n = 172

1 vs. 5, P = 0.0001, n =199
5 vs. 10, P = 0.2, n = 143
1 vs. 10, P = 0.0003, n = 172

P = 0.002, n = 143

Age, years

Menopausal

98.5%

100%

Mann–Whitney test

30 vs. 40, P = 0.4
40 vs. 50, P = 0.0004
50 vs. 60, P < 0.0001

35 vs. 45, P = 0.4
45 vs. 55, P < 0.0001
55 vs. 65, P = 0.004

40 vs. 50, P < 0.0001
50 vs. 60, P < 0.0001
60 vs. 70, P = 0.8

↓ **Table 7.** Serum Ferritin in Women, Non-Blood-Donors of Similar Age in the MONICA 1 and MONICA 10 Surveys
Age at examination	MONICA 1 (1984)	MONICA 10 (1994)	Mann–Whitney test
IQR: interquartile range.
40 years	n = 265	n = 215
Ferritin, µg/L, median (IQR)	39 (21–69)	42 (25–74)	P = 0.6
50 years	n = 249	n = 221
Ferritin, µg/L, median (IQR)	54 (30–84)	64 (37–110)	P = 0.002
60 years	n = 228	n = 203
Ferritin, µg/L, median (IQR)	88 (50–136)	98 (56–157)	P = 0.049

↓ Table 7. Serum Ferritin in Women, Non-Blood-Donors of Similar Age in the MONICA 1 and MONICA 10 Surveys

Age at examination

MONICA 1 (1984)

MONICA 10 (1994)

Mann–Whitney test

IQR: interquartile range.

40 years

n = 265

n = 215

Ferritin, µg/L, median (IQR)

39 (21–69)

42 (25–74)

P = 0.6

50 years

n = 249

n = 221

Ferritin, µg/L, median (IQR)

54 (30–84)

64 (37–110)

P = 0.002

60 years

n = 228

n = 203

Ferritin, µg/L, median (IQR)

88 (50–136)

98 (56–157)

P = 0.049

↓ **Table 8.** Correlations Between Body Mass Index and Serum Ferritin in Women, Non-Blood-Donors, in the MONICA Cohort
MONICA 1, age, years	MONICA 1, BMI (kg/m²)	BMI 1 vs. ferritin	MONICA 10, age, years	MONICA 10, BMI (kg/m²)	BMI 10 vs. ferritin	BMI 1 vs. BMI 10*	MONICA 10, BMI ≥ 25 kg/m²	BMI 10 ≥ 25 kg/m² vs. ferritin
*Mann–Whitney test. BMI: body mass index; SD: standard deviation; r_s: Spearman’s correlation coefficient.
30 (n = 305)	23.8 ± 3.9	r_s = 0.03 P = 0.6	40 (n = 323)	24.1 ± 4.2	r_s = −0.03 P = 0.7	P < 0.0001	93/323 (28.8%)	r_s = −0.03 P = 0.8
40 (n = 285)	25.6 ± 4.6	r_s = −0.01 P = 0.9	50 (n = 331)	25.7 ± 4.9	r_s = −0.02 P = 0.8	P = 0.8	150/331 (45.3%)	r_s = 0.05 P = 0.5
50 (n = 281)	26.2 ± 4.5	r_s = 0.06 P = 0.4	60 (n = 318)	26.2 ± 4.4	r_s = 0.15 P = 0.008	P = 0.9	180/318 (56.6%)	r_s = 0.02 P = 0.8
60 (n = 216)	25.8 ± 4.4	r_s = 0.09 P = 0.2	70 (n = 238)	25.8 ± 4.4	r_s = 0.05 P = 0.4	P = 0.9	124/238 (52.1%)	r_s = 0.11 P = 0.3
30–60 (n = 1,028)	25.3 ± 4.4	r_s = 0.07 P = 0.03	40–70 (n = 1,210)	25.5 ± 4.6	r_s = 0.12 P < 0.0001	P = 0.3	547/1,210 (45.2%)	r_s = 0.03 P = 0.3
Mann–Whitney test	30 vs. 40 years: P = 0.1 40 vs. 50 years: P = 0.02 50 vs. 60 years: P = 0.3			40 vs. 50 years: P < 0.0001 50 vs. 60 years: P = 0.02 60 vs. 70 years: P = 0.3

↓ Table 8. Correlations Between Body Mass Index and Serum Ferritin in Women, Non-Blood-Donors, in the MONICA Cohort

MONICA 1, age, years

MONICA 1, BMI (kg/m²)

BMI 1 vs. ferritin

MONICA 10, age, years

MONICA 10, BMI (kg/m²)

BMI 10 vs. ferritin

BMI 1 vs. BMI 10*

MONICA 10, BMI ≥ 25 kg/m²

BMI 10 ≥ 25 kg/m² vs. ferritin

*Mann–Whitney test. BMI: body mass index; SD: standard deviation; r_s: Spearman’s correlation coefficient.

30 (n = 305)

23.8 ± 3.9

r_s = 0.03
P = 0.6

40 (n = 323)

24.1 ± 4.2

r_s = −0.03
P = 0.7

P < 0.0001

93/323 (28.8%)

r_s = −0.03
P = 0.8

40 (n = 285)

25.6 ± 4.6

r_s = −0.01
P = 0.9

50 (n = 331)

25.7 ± 4.9

r_s = −0.02
P = 0.8

P = 0.8

150/331 (45.3%)

r_s = 0.05
P = 0.5

50 (n = 281)

26.2 ± 4.5

r_s = 0.06
P = 0.4

60 (n = 318)

26.2 ± 4.4

r_s = 0.15
P = 0.008

P = 0.9

180/318 (56.6%)

r_s = 0.02
P = 0.8

60 (n = 216)

25.8 ± 4.4

r_s = 0.09
P = 0.2

70 (n = 238)

25.8 ± 4.4

r_s = 0.05
P = 0.4

P = 0.9

124/238 (52.1%)

r_s = 0.11
P = 0.3

30–60 (n = 1,028)

25.3 ± 4.4

r_s = 0.07
P = 0.03

40–70 (n = 1,210)

25.5 ± 4.6

r_s = 0.12
P < 0.0001

P = 0.3

547/1,210 (45.2%)

r_s = 0.03
P = 0.3

Mann–Whitney test

30 vs. 40 years: P = 0.1
40 vs. 50 years: P = 0.02
50 vs. 60 years: P = 0.3

40 vs. 50 years: P < 0.0001
50 vs. 60 years: P = 0.02
60 vs. 70 years: P = 0.3