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Table 4 Age at First Birth and CVD – Cohort Studies (N = 14), by Year of Publication

From: Age at first birth and risk of later-life cardiovascular disease: a systematic review of the literature, its limitation, and recommendations for future research

Cohort Studies

First author, publication year

Age at first birth

No. in cohort

No. study outcomes

N (%)

Point estimate (+CI) a

Base model

Point estimate (+CI) a

Final model

Adjusted for or matched on. If underlined, also adjusted in base model.

Notes on study considerations and limitations.

Colditz

1987 [26]

<19

6671 b

3 (0.004)

 

1.3 (0.4–4.3)

c D: age; SE: - BM: - HB: - R: -

Very few events in the exposure category of <19. Short follow-up in a relatively young age group.

20–22

145,708

42 (0.029)

0.9 (0.6–1.2)

23–25

257,170

108 (0.042)

1 (ref)

26–29

151,206

82 (0.54)

1.1 (0.8–1.5)

≥ 30

77,091

35 (0.045)

0.8 (0.5–1.2)

Cooper

1999 [27]

15–24

7996 b

8 (0.100)

 

1.29 (0.5–3.0)

D: age; SE: - BM: - HB: - R: -

Number of outcomes very low in all exposure categories

25–29

17,698

14 (0.079)

1 (ref)

30–32

5341

3 (0.056)

0.71 (0.2–2.5)

33–43

3715

8 (0.215)

2.9 (1.2–6.9)

Otterblad- Olausson

2004 (CVD) [9]

<20

60,686

41 (0.07)

2.2 (1.5–3.1)

1.8 (1.2–2.6)

D: age; SE: background SES in 1960 (parents), socio-economic position (‘90), family situation (‘90), welfare dependency (‘90) BM: - HB: - R: Parity

Conducted amongst women aged 30–45, follow-up time of 5 years, resulting in low number of events. Some women still having children.

20–29

399,748

110 (0.03)

1 (ref)

1 (ref) d

Otterblad- Olausson

2004 (CHD) [9]

<20

60,686

Data not

2.8 (1.5–5.4)

2.2 (1.2–4.3)

20–29

399,748

provided

1 (ref)

1 (ref) d

Otterblad- Olausson

2004 (CeVD) [9]

<20

60,686

Data not

1.5 (0.8–2.9)

1.4 (0.7–2.7)

20–29

399,748

provided

1 (ref)

1 (ref) d

Yang CY 2006

<26

859,942

102 (0.012)

1 (ref)

 

D: - SE: - BM: - HB: - R: Parity

No adjustment for participant age is reported (while due to study set-up women with older age at first birth were older at follow-up). Cut-off for youngest group <26

26–30

372,895

70 (0.019)

1.78 (1.3–2.4)

≥ 31

59,625

17 (0.029)

2.96 (1.8–5.0)

Continuous

  

1.10 (1.06–1.1)

1.08 (1.04–1.1)

Henretta

2007

Heart disease [30]

<20

991

Data not provided

 

0.36 (P:<.01)

D: age, race, US-born, unmarried at first birth, marital status; SE: Father’s education, education, log net worth, log income; BM: - HB: - R: Birth >39, birth interval, parity

No information on the number of outcomes per exposure group; no confidence intervals

≥ 20

2956

Henretta

2007

Stroke [30]

<20

991

Data not provided

 

−.03

P-value or CI not provided

≥ 20

2956

Sakauchi 2007

CHD [36]

<23

Data not provided

121

 

1.09 (0.8–1.5)

D: age, study area; SE: - BM: - HB: - R: -

No denominator information provided

23–25

116

1 (ref)

≥ 26

131

1.17 (0.9–1.5)

Sakauchi

2007

(CeVD) [36]

<23

Data not provided

291

 

1.19 (0.99–1.4)

23–25

294

1 (ref)

≥ 26

326

1.07 (0.9–1.3)

Yang L

2009, Ischemic stroke [39]

<23

11,942

68 (0.57)

1.1 (0.7–1.5)

1.0 (0.6–1.5)

D: age; SE: education; BM: BMI, high blood pressure, DM; HB: alcohol, smoking, physical activity; R: -

Young age at first birth category not compared to lowest risk category. Few cases for hemorrhagic stroke.

21–25

9905

49 (0.49)

1 (ref)

1 (ref)

≥ 26

17,444

48 (0.28)

0.6 (0.4–0.9)

0.7 (0.4–1.1)

Yang L

<21

11,942

28 (0.23)

2.0 (1–4)

1.8 (0.8–4.1)

2009

hemorrhagic stroke

21–25

9905

11 (0.11)

1 (ref)

1 (ref)

  

≥ 26

17,444

19 (0.11)

1.1 (0.5–2.3)

1.2 (0.5–2.6)

Grundy

2010 [29]

Women

<20

862,007 b

572 (0.07)

1.47 (1.3–1.6)

1.22 (1.1–1.3)

D: age, year, region residence, log population size, marital status; SE: level of education; BM: - HB: - R: parity

 

20–24

3,200,462

1567 (0.05)

1 (ref)

1 (ref)

25–29

1,670,417

574 (0.03)

0.67 (0.6–0.7)

0.81 (0.7–0.9)

≥ 30

646,983

224 (0.03)

0.60 (0.5–0.7)

0.78 (0.7–0.9)

Grundy

2010

Men [29]

<23

1,164,183 b

2190 (0.19)

1.39 (1.3–1.5)

1.23 (1.2–1.3)

23–28

3,238,174

4804 (0.15)

1 (ref)

1 (ref)

29–34

1,313,342

1772 (0.13)

0.88 (0.8–0.9)

0.93 (0.9–0.99)

≥ 35

473,472

571 (0.12)

0.87 (0.8–0.95)

0.93 (0.9–1.01)

Chang

2011

CVD [25]

15–19

844

144 (17.1)

1.00 (ref)

1.00 (ref) d

D: age at entry; SE: education, occupation; BM: BMI, HT HB: drinking, smoking R: -

For CVD there was a mention of a fourth model in which the authors additionally corrected for reproductive variables and marital status, which did not change the findings.

Extensive adjustment in final model. Few CHD events.

20–22

1646

230 (14.0)

0.74 (0.6–0.9)

0.74 (0.6–0.9)

≥ 23

787

104 (13.2)

0.75 (0.6–0.96)

0.76 (0.6–0.98)

Chang

2011

CHD [25]

15–19

844

12 (1.42)

1.00 (ref)

1.00 (ref) d

20–22

1646

24 (1.46)

0.88 (0.4–1.8)

0.89 (0.4–1.8)

≥ 23

787

11 (1.40)

0.93 (0.4–2.1)

0.90 (0.4–2.1)

Chang

2011

Stroke [25]

15–19

844

87 (10.3)

1.00 (ref)

1.00 (ref) d

20–22

1646

142 (8.6)

0.76 (0.6–0.99)

0.78 (0.6–1.02)

≥ 23

787

68 (8.6)

0.80 (0.6–1.1)

0.84 (0.6–1.2)

Gallagher

2011

CHD [28]

<20

12,460

43 (0.35)

 

0.93 (0.7–1.3)

D: age; SE: - BM: - HB: - R: -

Young age at first birth category not compared to lowest risk category.

20–24

72,570

239 (0.33)

1 (ref)

25–29

124,044

101 (0.08)

0.75 (0.6–0.95)

≥ 30

45,041

37 (0.08)

0.85 (0.6–1.2)

Gallagher

2011

Ischemic stroke [28]

<20

12,460

75 (0.60)

 

1.23 (0.96–1.6)

20–24

72,570

309 (0.43)

1 (ref)

25–29

124,044

141 (0.11)

0.88 (0.7–1.1)

≥ 30

45,041

50 (0.11)

0.95 (0.7–1.3)

Gallagher

2011

Hemorrhagic

Stroke [28]

<20

12,460

178 (1.43)

 

1.09 (0.9–1.3)

20–24

72,570

850 (1.17)

1 (ref)

25–29

124,044

423 (0.34)

0.84 (0.7–0.9)

≥ 30

45,041

132 (0.29)

0.81 (0.7–0.97)

Webb

2011 [10]

N/A

1,021,417 b

46 (0.0045)

 

1 (ref)

D: age, decade; SE: - BM: - HB: - R: -

Few events in <20 category. Nulliparous group includes young women who did not have children yet.

<20

159,716

16 (0.0100)

1.25 (0.7–2.2)

≥ 20

732,462

71 (0.0097)

0.93 (0.6–1.4)

<20

159,716

16 (0.0100)

1.35 (0.8–2.3)

≥ 20

732,462

71 (0.0097)

1 (ref)

Merritt

2015

(FTP)

(CVD) [32]

<21

39,201

304 (0.78)

 

1.15 (0.99–1.3)

D: age, site; SE: education; BM: BMI; HB: physical activity, smoking (duration and intensity); R: menopausal status.

Extensive adjustment in final model and no unadjusted model for comparison.

21–23

71,322

497 (0.70)

1.11 (0.98–1.3)

24–25

52,056

359 (0.69)

1.05 (0.9–1.2)

26–30

75,927

557 (0.73)

1 (ref)

≥ 31

27,027

237 (0.88)

1.06 (0.9–1.2)

Merritt

2015

(FTP)

(CeVD) [32]

<21

39,201

97 (0.25)

 

1.14 (0.9–1.5)

21–23

71,322

150 (0.21)

0.96 (0.8–1.2)

24–25

52,056

122 (0.23)

1 (ref)

26–30

75,927

199 (0.26)

0.97 (0.8–1.2)

≥ 31

27,027

79 (0.29)

0.90 (0.7–1.2)

Merritt

2015

(FTP)

(CHD) [32]

<21

39,201

105 (0.27)

 

1.14 (0.9–1.5)

21–23

71,322

140 (0.20)

0.96 (0.7–1.2)

24–25

52,056

106 (0.20)

1 (ref)

26–30

75,927

166 (0.22)

0.99 (0.8–1.3)

≥ 31

27,027

74 (0.27)

1.10 (0.8–1.5)

Barclay

2016

Women [22]

15–19

2998

1148 (38.3)

1.18 (1.1–1.3)

1.25 (1.1–1.4)

D: birth cohort [2]; SE: (sibling fixed effect model) age of person’s mother at time of their own birth, attained socioeconomic status, educational attainment, marital status; BM: - HB: - R: Completed parity

 

20–24

5232

1894 (36.2)

1.11 (1.02–1.2)

1.23 (1.1–1.4)

25–29

3052

1022 (33.5)

1 (ref)

1 (ref)

30–34

1010

322 (31.9)

0.94 (0.8–1.1)

0.89 (0.7–1.1)

35+

343

120 (35.0)

1.14 (0.9–1.4)

1.09 (0.8–1.5)

Barclay

2016

Men [22]

15–19

1469

661 (45.0)

1.45 (1.3–1.6)

1.37 (1.2–1.6)

20–24

9380

3595 (38.3)

1.11 (1.1–1.2)

1.10 (1.03–1.2)

25–29

9533

3395 (35.6)

1 (ref)

1 (ref)

30–34

4590

1623 (35.4)

0.98 (0.9–1.04)

1.03 (0.9–1.1)

35+

2211

793 (35.9)

0.98 (0.9–1.1)

0.97 (0.9–1.1)

Parikh

2016 [35]

Nullipara

10,462

Data not provided. Total cases: 4607

 

1.00 (0.9–1.1)

D: age at enrollment; SE: income, education, neighborhood SES variables; BM: history of high cholesterol requiring pills, hypertension, diabetes; HB: smoking; nr of still births, nr of miscarriages, breastfed for >1 month

Extensive adjustment in final model

<20

8780

1.65 (1.5–1.8)

1.27 (1.1–1.4)

20–24

29,803

1.25 (1.2–1.4)

1.14 (1.1–1.2)

≥ 25

23,937

1 (ref)

1 (ref)

  1. D demographics, SE Socio-economic, BM Biomedical, HB Health behavior, R Reproductive, AFB age at first birth, AFP age at first pregnancy, HT hypertension, DM diabetes mellitus, CHD coronary heart disease, CeVD cerebrovascular disease, SES socio-economic status, BMI body mass index, FTP full term pregnancy
  2. aRisk estimates used: Relative risk: Yang C, Yang L, Barclay. Rate ratio: Colditz, Cooper, Otterblad, Webb. Hazard ratio: Chang, Gallagher, Merritt, Sakauchi. Odds ratio: Grundy, Parikh. Log odds ratio: Henretta
  3. bPerson years rather than individuals in group. Percentage is based on N / person years
  4. cAuthors indicate that a multivariate model yielded the same/similar results
  5. dFor intermediate models, see original publications
  6. The bold data indicate significant results