Fertility history and later life health: is the association mediated or moderated by physical activity ? Emily Grundy and Sanna Read .

Fertility history and later life health: is the association mediated or moderated by

physical activity ?

Emily Grundy and Sanna Read

http://pathways.lshtm.ac.uk [email protected]

@PathwaysNCRM

Physical activity, parenthoodhistories and health in later life

• Early parenthood, high parity and nulliparity are associated with worse later life health in women and men in England and various other countries

• This association may reflect several direct and indirect mechanisms • Health related behaviours such as physical activity may mediate the

association, or moderate effects• It is also important to take into account other health related behaviours such

as smoking, and socioeconomic position and social support.

http://pathways.lshtm.ac.uk


How does physical activity promote health and physical functioning ?– improved body composition – healthy lipid levels– glucose homeostasis and insulin sensitivity– blood circulation– reduced blood pressure and inflammation

How might fertility history influence physical activity ?– parents more likely to adopt health promoting behaviours than childless;

activities with children may involve participation in physical activities – and this may be carried forward into post childrearing phase of life

– however, some types of fertility trajectory (early parenthood and large family size) may be assocaited with a less healthy lifestyle



• Does physical activity moderate the health risks related to parity and early birth ?– Previous research shows that in new mothers physical activity reduces

post- pregnancy overweight – Whether or not physical activity moderates the association between

fertility history and later life health not previously investigated


Aim

• To investigate whether physical activity mediates or moderates the association between fertility histories and later life health in older men and women.


Parenthood history

Health

Demographic and life history factors

Is the association between parenthood history and health mediated by physical activity?

The mediation model to be tested

Physical activity

Parenthood history

Health


Is the association between parenthood history and health mediated by physical activity?

The mediation model to be tested

Physical activity

Parenthood history

Functional limitations

(initial level and rate of change)


Does physical activity moderate the association between parenthood history and health?

The moderation model to be tested

Physical activity

Data

• English Longitudinal Study of Ageing (ELSA) waves 1 - 5 (2002-2010) - nationally representative survey of men and women aged 50+ (mean age = 63, SD = 9.2 in wave 1)

• Socio-demographic information and self reported health collected in all waves

• Detailed health data including biomarkers collected in alternate waves –biomarker data used to derive an index of allostatic load

• Retrospective life course data collected in wave 3. Analysis based on those providing life course data (n = 6207)


MeasuresDemographic & life course:

Age, education, childhood health problem (retrospective), married/not married, and co-residence with child (time varying); ever divorced, ever widowed (wave 3).

Parenthood history: Number of natural children (0, 1,2,3,4+); any step child; any adopted child; deceased child; for parents: young (<20/23) age first birth; late age last birth (>34/39).

Intermediate measures: Physical activity; wealth; smoking; social support and strain (Wave 1)

Health outcomes: Allostatic load (wave 2); limiting long-term illness (wave 3); functional limitations (waves 1-5).


Allostatic load scores in ELSA• Allostatic load: multisystem physical dysregulation resulting from long-term exposure to stress• Grouped allostatic load index: number of biomakers indicating high risk (upper 25th percentile,

except for peak expiratory flow lower 25th percentile) calculated separately for men and women (and age group), weighted by the number of markers per system and adjusted for medication


System Biomarker

Cardiovascular Systolic blood pressure

Diastolic blood pressure

Inflammation Fibrinogen

C-reactive protein

Lipid metabolism Triglycerides

Glycosylated haemoglobin

Total/HDL cholesterol ratio

Body fat Waist/hip ratio

Respiratory Peak expiratory flow

Associations between fertility & parenthood variables, allostatic load and health limitation among men and women in ELSA

Allostatic load Health limitation

No. Natural children (ref = 2) Men Women Men Women

0 -0.05 0.04 0.10 0.18

1 0.04 -0.14 0.14 0.07

3 0.01 0.18 0.07 -0.01

4+ 0.34* 0.29* 0.29* 0.23*

Early child birtha 0.51*** 0.58*** 0.46*** 0.43**

Late childbirtha 0.10 -0.16 0.29* -0.23*

Adopted child -0.15 0.55** -0.24 0.09

Step child 0.08 0.03 0.30* -0.09

Child died 0.22 0.03 0.21 0.19

Models include health in childhood; age; education; married/not married; ever widowed; ever divorced; intergenerational contact. Allostatic load adjusted for fasting & inhaler use. a parents only.

Associations between parity and physical activity in ELSA

0 1 2 3 4+0%

20%

40%

60%

80%

100%

Sedentary or mild Moderate at least once a week

Vigorous at least once a week

0 1 2 3 4+0%

20%

40%

60%

80%

100%

Men

Women

Number of children

Physical activity

Associations between early parenthood and physical activity in ELSA

No early childbirth Early childbirth0%

20%

40%

60%

80%

100%

Sedentary or mildModerate at least once a weekVigorous at least once a week

Physical activity

Men Women

No early childbirth Early childbirth0%

20%

40%

60%

80%

100%

Sedentary or mildModerate at least once a weekVigorous at least once a week

Physical activity

Results: Mediation


Adopted child

Wealth

Wave 1 Wave 2 Wave 3

Allostatic load

Limiting long-term illness

Children4 vs. 2

Smoking

Social strain

-0.45 (0.167)

-0.15 (0.025)

0.10 (0.021)

0.47 (0.09)0.71 (0.153)

0.12 (0.037) 0.28 (0.084)

Figure 1. Path model for all women in ELSA. Model adjusted for age, education, being married, ever divorced, ever widowed and childhood health. Significant paths are shown (unstandardized estimate and standard error). Source: Analysis of ELSA waves 1-3.

-0.58 (0.078)

Physical activity

-0.38 (0.040)

-0.61 (0.046)

-0.10 (0.028)

-0.19 (0.053)

Wealth


Allostatic load


Children4 vs. 2

-0.74 (0.092)

-0.13 (0.030)

-0.35 (0.048)

0.12 (0.023)-0.32 (0.069)

Figure 2. Path model for all men . Model adjusted for age, education, being married, ever divorced, ever widowed and childhood health. Significant paths are shown (unstandardized estimate and standard error). Source: Analysis of ELSA waves 1-3.

Smoking

Social strain

Physical activity

0.93 (0.174)

0.11 (0.037)

0.62 (0.099)

0.24 (0.086)

0.39 (0.097)

-0.63 (0.053)

-0.13 (0.027)

Wealth


Allostatic load


Early childbirth

Physical activity

Smoking

-0.52 (0.088) -0.14 (0.030)

0.09 (0.024)

-0.40 (0.049)

-0.39 (0.075)

0.48 (0.156)

-0.63 (0.055)

0.50 (0.109)

Figure 3. Path model for biological mothers. Model adjusted for age, education, being married, ever divorced, ever widowed ,childhood health, and coresidence with child. Significant paths are shown (unstandardized estimate and standard error). Source: Analysis of ELSA waves 1-3.

-0.24 (0.059)

0.38 (0.147)

-0.09 (0.034)

Wealth


Allostatic load


Early childbirth

Smoking

-0.43 (0.093) -0.15 (0.033)

0.12 (0.027)

0.41 (0.131)

-0.14 (0.056)

Figure 4. Path model for biological fathers. Model adjusted for age, education, being married, ever divorced, ever widowed, childhood health, and coresidence with child. Significant paths are shown (unstandardized estimate and standard error).Source: Analysis of ELSA waves 1-3.

-0.38 (0.066)

0.30 (0.149)

Physical activity

0.36 (0.164)

0.79 (0.132)

-0.10 (0.036)

-0.64 (0.066)

Results: Moderation


T1 T2 T3 T4 T50

0.5

1

1.5

2

2.5

3

Less than vigorous activity + 0 childrenLess than vigorous activity + 1 childLess than vigorous activity + 2 children Less than vigorous activity + 3 childrenLess than vigorous activity + 4 or more childrenVigorous activity + 0 childrenVigorous activity + 1 childVigorous activity + 2 children Vigorous activity + 3 children Vigorous activity + 4 or more childrenEs

timat

ed le

vel o

f fun

ction

al li

mita

tions

Men

T1 T2 T3 T4 T50

0.5

1

1.5

2

2.5

3

Less than vigorous activity + 0 childrenLess than vigorous activity + 1 childLess than vigorous activity + 2 children Less than vigorous activity + 3 childrenLess than vigorous activity + 4 or more childrenVigorous activity + 0 childrenVigorous activity + 1 childVigorous activity + 2 children Vigorous activity + 3 children Vigorous activity + 4 or more childrenEs

timat

ed le

vel o

f fun

ction

al li

mita

tions

Women

T1 T2 T3 T4 T50

0.5

1

1.5

2

2.5

3

3.5

Less than vigorous activity + early childbirthLess than vigorous activity + no early childbirthVigorous activity + early childbithVigorous activity + no early childbirth

Estim

ated

leve

l of f

uncti

onal

lim

itatio

nsMen

T1 T2 T3 T4 T50

0.5

1

1.5

2

2.5

3

3.5

Less than vigorous activity + early childbirthLess than vigorous activity + no early childbirthVigorous activity + early childbithVigorous activity + no early childbirth

Estim

ated

leve

l of f

uncti

onal

lim

itatio

nsWomen

Conclusions & Discussion

• Physical activity mediates the association between high parity and later life health. It also partially mediates the association between early parenthood and later life health.

• Mediation through physical activity is not as strong as through wealth.

• Physical activity moderates the levels of health disadvantage related to high parity and early childbirth

• Low parity (nulliparity, having 1 child compared to 2 children) was not associated with lower levels of physical activity or poorer health

• Important to investigate early life pathways to particular fertility trajectories- especially childhood SES and broader environmental influences (e.g. support from the state)


Sample derivation and data availability


WAVE 1

Core sample members n = 11392 Interview items available n = 10133

WAVE 2

Core sample members n = 8781

Interview items available n = 8779

Nurse visit: allostatic load score available n = 6187

All items available waves 1, 2 and 3

n = 4378

WAVE 3

Core sample members n = 7535

Interview items available n = 7191

Life history: fertility history available n = 6207

Allostatic load: 25th percentile high risk cut-off points, ELSA in wave 2 (2002).

Men Women

Aged 51-65 Aged 65+ Aged 51-65 Aged 65+

Inflammation (n = 1008-1017) (n = 982-986) (n = 1219-1232) (n = 1190-1196)

C-reactive protein >2.9 >3.4 >3.4 >3.9

Fibrinogen >3.4 >3.7 >3.5 >3.8

Cardiovascular (n = 1074) (n = 1106) (n = 1319) (n = 1398)

Systolic blood pressure >143 >149 >140 >151

Diastolic blood pressure >85 >80 >83 >79

Lipid metabolism (n = 1001-1017) (n = 965-983) (n = 1219-1233) (n = 1187-1196)

HDL/Total cholesterol ratio >5.0 >4.6 >4.4 >4.5

Triglycerides >2.5 >2.2 >2.1 >2.1

Glycosylated haemoglobin >5.7 >5.9 >5.6 >5.8

Body fat (n = 1216) (n = 1231) (n = 1486) (n = 1527)

Waist/hip ratio >1.00 >1.00 >0.88 >0.89

Respiratory (n = 1197) (n = 1190) (n = 1415) (n = 1437)

Peak expiratory flow <506 <406 <344 <265

No qualifica

tion

Marr

ied

Ever d

ivorce

d

Ever w

idowed

Long-t

erm healt

h problem in

child

hood0

102030405060708090

Distribution of the sample by demographic & life history variables

MenWomen

%

Coresident with child

Weekly contact

with child

Has adopted child

Has step child Has a child who died

0

5

10

15

20

25

30

35

40

45

50


MenWomen

%

0 1 2 3 4+ Early childbirth

Late childbirth

0

5

10

15

20

25

30

35

40

45


MenWomen

%

Number of children

<0.1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-1.00

5

10

15

20

25

30

35

40

Distribution of the health outcomes

MenWomen

%

Allostatic load weighted means scoreHealth limitation

Distribution of the sample by intermediate variables in wave 1, Mean (SD) or %

Men Women Wealth quintile 3.4 (1.38) 3.2 (1.39) Physical activity 2.2 (0.73) 2.1 (0.78) Current smoking 13.9 15.5 Perceived social support 4.2 (0.50) 4.3 (0.49) Perceived social strain 2.7 (0.42) 2.6 (0.45)

Fertility history and later life health: is the association mediated or moderated by physical activity ? Emily Grundy and Sanna Read .

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