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Sustainable Human Development Across the Life CourseEvidence from Longitudinal Research$

Prerna Banati

Print publication date: 2021

Print ISBN-13: 9781529204827

Published to Policy Press Scholarship Online: September 2021

DOI: 10.1332/policypress/9781529204827.001.0001

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Early Life Transitions Increase the Risk for HIV Infection: Using Latent Class Growth Models to Assess the Effect of Key Life Events on HIV Incidence Among Adolescent Girls in Rural South Africa

Early Life Transitions Increase the Risk for HIV Infection: Using Latent Class Growth Models to Assess the Effect of Key Life Events on HIV Incidence Among Adolescent Girls in Rural South Africa

Chapter:
(p.69) 3 Early Life Transitions Increase the Risk for HIV Infection: Using Latent Class Growth Models to Assess the Effect of Key Life Events on HIV Incidence Among Adolescent Girls in Rural South Africa
Source:
Sustainable Human Development Across the Life Course
Author(s):

Audrey Pettifor

Emily Agnew

Torsten B. Neilands

Jennifer Ahern

Stephen Tollman

Kathleen Kahn

Sheri A. Lippman

Publisher:
Policy Press
DOI:10.1332/policypress/9781529204827.003.0004

Abstract and Keywords

Adolescent girls and young women (AGYW) in sub-Saharan Africa are at very high risk of HIV infection. 6% of adolescent AGYW ages 15-19 are infected with HIV, increasing to over 17% by age 20-24. Adolescents matter and yet we have limited, rigorous information on what matters for adolescents living in developing countries and how we can best help them transition safely to adulthood. This chapter uses longitudinal data on a cohort of over 2,000 adolescent girls in rural South Africa who have been followed over 8 years as they transition from adolescence into early adulthood to examine how the timing and occurrence of multiple, non-repeatable social and behavioral determinants shape the risk of HIV acquisition over the adolescent life course. The analysis uses multiple event process survival mixture modeling to examine how key exposures such as childhood sexual abuse, depression, household shocks, poverty, parental loss, early pregnancy, school leaving and gender based violence shape HIV risk during adolescence. This is a unique opportunity to examine key behavioral and social life events in combination and longitudinally among young women in rural Africa, providing unique insights into when best to intervene and on what.

Keywords:   Adolescents, HIV, South Africa, Social determinants, School, Depression, Poverty, Gender Based Violence

Introduction

Adolescent girls and young women (AGYW) in sub-Saharan Africa are at high risk of HIV infection. HIV infection rates increase substantially among AGYW after the age of 18. In South Africa HIV prevalence rises from 6% among young women aged 15–19 years to 17% by ages 20–24. This age period marks a time of transition into adulthood and coincides with a number of key life events, such as finishing the mandatory years of schooling, leaving home, entering first sexual relationships and experiencing first pregnancies.(Human Sciences Research Council [HSRC], 2017) Key life events that include first pregnancy, coital debut, leaving school and parental death have all been found independently to be associated with an increased risk of HIV infection in young women. Young women who experience their first vaginal sex before the age of 15 are more likely to be living with (p.70) HIV, and these early events are often characterized by forced sex and sex with older male partners who are more likely to be HIV infected (Pettifor et al, 2004, 2009; Wand and Ramjee, 2012). While school attendance has multiple developmental and later life benefits, leaving school increases the risk of HIV acquisition. Girls who do not attend school as often and who drop out are more likely to acquire HIV infection than those attending and who stay in school (Stoner et al, 2017) In one study, this association appears to be explained by school environments providing safer spaces where adolescent girls are more likely to have male partners closer in age and also have fewer sexual partners than those out of school (Stoner et al, 2018) Similar patterns have been observed for young women experiencing early adolescent pregnancy (before the age of 15), whereby HIV incidence is much higher, and those who experience adolescent pregnancy also have more risk factors for HIV infection such as older partners and more sexual partners (Christofides et al, 2014). Finally, loss of a parent has been found to be associated with HIV risk in young people; orphaned youth are more likely to be living with HIV and to report riskier sexual behaviour than non-orphaned youth (Operario et al, 2011).

Despite documentation of the importance of life event to HIV risk, little is understood about the timing of key life events and how they shape HIV risk as adolescents transition into adulthood. While coital debut, pregnancy and leaving school are all key life transitions that many young people will experience as part of their expected life course (MacMillan and Copher, 2005), occurrence earlier in adolescence can result in negative outcomes for health and development (Evans et al, 2013). Life course theory highlights that the timing and sequence of life events or transitions result in different meaning and consequences (Elder, 1998). While experience of particular life events earlier may have immediate impacts on health and social factors, their impacts may also extend into the future by affecting subsequent transitions (Elder, 1998). While there is a robust body of literature documenting how adverse child events can impact health in adulthood (Hughes et al, 2017), this evidence is just starting to emerge from low-and middle-income countries (Kidman and Kohler, 2019). Further, negative life events that occur in early adolescence (ages 9–14), when major brain and social transitions are occurring, may have long-lasting consequences (Falconi et al, 2014; UNICEF, 2017). However, changes that occur in early adolescence in the brain may also provide an opportunity for intervention to improve future health and developmental trajectories (Fuhrmann et al, 2015; UNICEF, 2017). Life course research that examines how the timing of events in earlier life can impact later (p.71) life health aligns well with understanding progress in meeting the Sustainable Development Goals (SDG). SDG 3, which supports ensuring healthy lives and promoting well-being for all at all ages is particularly well aligned to better understanding how earlier life events can impact health later in life. Thus, better understanding of how the timing of key events, in particular using longitudinal data, can impact HIV risk across the life course can help target prevention programmes to address vulnerable time periods in the transition to adulthood to reduce new infections, helping to achieve the SDGs which include reducing new HIV infections.

The purpose of this research was to explore the impact of key life events, specifically sexual debut, pregnancy, death of a parent and leaving school, on HIV incidence among a cohort of AGYW in rural South Africa. This research utilized latent class growth analysis (LCGA) to classify adolescent girls based on growth trajectories according to the age at which they experienced these life events. In addition, LCGA was used to examine the cumulative impact of multiple key life events within the same time period of these young women’s lives, and how these events affected their risk of HIV acquisition as they aged.

Methods

Study design

The HIV Prevention Trials Network (HPTN) 068 was a phase 3 randomized controlled trial to determine whether a monthly cash transfer, conditional on school attendance, would reduce HIV incidence for adolescent girls and young women in South Africa (Pettifor et al, 2016). The study was undertaken by the Medical Research Council/Rural Public Health and Health Transitions Research Unit, which runs the Agincourt Health and Socio-Demographic Surveillance System (HDSS) site in the rural Bushbuckridge subdistrict in Mpumalanga province, South Africa.

Women aged 13–20 years were included in the HPTN 068 study if they were enrolled in school grades 8–11 of the South African government educational system, HIV negative, not married or pregnant, able to read, able to open a bank account, and currently residing in the study area. Potential participants were identified from the Agincourt HDSS sampling frame. Each young woman and her parent or guardian provided written informed consent. Written assent was obtained for those younger than 18 years. Consent and assent forms were available in English and Shangaan.

(p.72) Participants completed an interview using audio computer-assisted self-interview (ACASI) which collected information on sexual behaviour, mental health, sexual and physical abuse, pregnancy history and contraceptive use, schooling and other sociodemographic information at baseline and at 12, 24 and 36 months until the study completion date or their planned high-school completion date, whichever came first. HIV and Herpes Simplex Virus (HSV-2) testing were also conducted at each of these visits. HIV screening was done with two HIV rapid tests completed in parallel – the Determine HIV-1/2 test (Alere Medical Co, Matsudo-shi, Chiba, Japan) and the US Food and Drug Administration (FDA)-cleared Uni-gold Recombigen HIV test (Trinity Biotech, Bray, County Wicklow, Ireland). Further details of the study design can be found in the main study paper (Pettifor et al, 2016).

Institutional Review Board approval for this study was obtained from the University of North Carolina at Chapel Hill and the University of the Witwatersrand Human Research Ethics Committee.

Statistical analysis

Latent class growth models are a method for fully capturing information about between-person differences in within-person patterns of change over time. Individuals are grouped into latent classes based upon similar patterns of data over time. The method assumes that the observed distribution of values may be a combination of two or more subpopulations whose membership is unknown. As such, latent class growth analysis probabilistically assigns individuals to these subpopulations by inferring each individual’s membership to latent classes from the observed growth model data. Life events at different stages in life can be classified as separate events to investigate how the event and when it happens affects the individual’s risks of HIV infection.

The classes of different life event trajectories over time were categorized using LCGA, allowing the individual’s variation to occur around one of multiple trajectories. After classifying life event trajectories, it was determined which trajectories were predictors of the outcome, HIV status. Each class therefore described a course over time of each of the four life events: sexual debut, pregnancy, leaving school and death of a parent. Each trajectory was determined over four time points: whether the event occurred by age 14, by age 17, by age 21 and by age 23. However, for the ‘leaving school’ model all participants had left by age 23 and so the trajectories are determined (p.73) over only the first three time points. In addition, LCGA was applied to describe temporal patterns in multiple life events over the same time points of these young women’s lives, and examine the relation of these patterns to HIV. In addition to the binary variable for whether participants had experienced one of the events by a particular age, a variable was also modelled that sums the number of events an adolescent girl had experienced by each age. All the life events in the model were included: sexual debut, first pregnancy, leaving school and the death of a parent. The analysis was conducted using Mplus version 8 (Muthén and Muthén, 2005) and Stata version 15 (StataCorp, 2017).

Models were fitted over a range of class numbers to identify the ideal number of classes in describing patterns in the timing of all life events. Models were also fitted for each of the life events – sexual debut, pregnancy, leaving school and death of a parent –, over a range of class numbers. Two to four classes were examined for the individual life events and three to six for the combined classes. The model fitting is provided in Table 3.1. Fit was assessed using the Bayesian Information Criterion (BIC), the Bootstrap likelihood ratio tests (BLRT) and entropy values (Jung and Wickrama, 2008). In addition to model fit statistics, the interpretability and practical coherence of the model classes were considered. The models were run with multiple random starting values to avoid settling on local solutions; each model was run with 100 random starts and 10 final optimizations. These values were increased when convergence was not achieved. Having determined the best fitting model, the latent classes were added to a generalized linear model (GLM), regressing HIV status on the latent class trajectories of the life events, using a binomial distributional family and log link, to estimate the risk ratio (RR) of HIV infection for each latent class.

Finally, dominance analysis, a technique which rank-ordered the relative importance or contribution of the life events classes in predicting HIV incidence, was used based on the individual variables’ contribution to the overall model fit. This method is based on the average pseudo R2 explained by each life event across all possible subsets regression models (Azen and Traxel, 2009; Budescu, 1993).

Missing data

Parameter estimates from Mplus were adjusted for missingness using a robust full information maximum likelihood (FIML) estimator, which assumes data is missing at random. Mplus generates the covariance coverage matrix to assess the proportion of observations available for each pair of variables, the minimum recommended coverage in Mplus (p.74) is 10%; the coverage proportions among the variables in this analysis were all greater than 42.5%, verifying the use of the FIML estimator for this analysis.

Measures

The study looked at events that could occur at only one time and where the timing of the event could be measured (for example, left school at age 15) so that the temporality of exposure and outcome (HIV sero-conversion) could be assessed. In order to assess time since exposure on the outcome, coital debut was measured by asking young women whether they had ever had vaginal sex and if yes, at what age they first had vaginal sex. For pregnancy, young women were asked if they had ever been pregnant and if so the age at first pregnancy. For school leaving, young women were asked if they were still attending secondary school or not and the age they left secondary school. Parental death was assessed by asking, separately, if their mother and father were alive, and if not what age the young person was when they died. Measures were adjusted for the following covariates: age at enrolment, length of study enrolment, trial arm, school attendance, anxiety, depression, interpersonal violence (IPV) and HIV knowledge.

Results

Specific life events and HIV incidence

Figure 3.1 shows the observed and expected trajectories from the LCGA model, for each of the life events. The selected models included two linear trajectory classes for leaving school and death of a parent and three linear trajectory classes for sexual debut and pregnancy.

In Figure 3.1a, the trajectories for leaving school, a two-class model fit the data best, with classes identified as those who leave school early (class 1) and those leaving later (class 2). Table 3.1 shows the unadjusted and adjusted risk ratios (RR) for the log-binomial regression of the two classes on HIV infection; the risk of HIV infection in those who leave school early (class 1) is 2.9 times higher (p-value = 0.001) than those who leave later (class 2) in the unadjusted model. When the model is adjusted for age at enrolment and length of enrolment, the participants’ risk ratio increases to 4.3 (p-value < 0.001) (Table 3.1).

Figure 3.1b shows the three-class model trajectories for sexual debut, with those with an ‘early’ debut (class 2), those with no debut or a (p.75) ‘late’ debut (class 3) and those with a debut between these (class 1). Compared to those with a ‘late’ debut, the risk of HIV infection of class 1 is 2.1 times higher (p-value = 0.05) and the risk of class 2 is 2.8 times higher (p-value = 0.01), when adjusted for age at enrolment and length of enrolment (Table 3.1).

Early Life Transitions Increase the Risk for HIV Infection: Using Latent Class Growth Models to Assess the Effect of Key Life Events on HIV Incidence Among Adolescent Girls in Rural South AfricaEarly Life Transitions Increase the Risk for HIV Infection: Using Latent Class Growth Models to Assess the Effect of Key Life Events on HIV Incidence Among Adolescent Girls in Rural South Africa

Figure 3.1: Latent class growth analysis observed and expected trajectories

Source: Author’s own

Figure 3.1c shows a three-class model for pregnancy, with those with an ‘early’ first pregnancy (class 3), those with no pregnancy or a ‘late’ first pregnancy (class 2) and those with a first pregnancy between these (class 1). Compared to those with a ‘late’ first pregnancy, the risk of HIV infection of a neither late nor early pregnancy (class 1) is 1.6 times higher (p-value = 0.04) and the risk of an early pregnancy (class 3) is 2.8 times higher (p-value = 0.01), when adjusted for age at enrolment and length of enrolment.

Figure 3.1d shows the two-class model trajectories for the death of a parent. The two classes are those who do not experience a death or (p.76) experience it later (class 1) and those who experience it earlier (class 2). The risk of HIV infection in those who experience a death earlier (class 2) is 2.0 times higher (p-value < 0.001) than those who do not or experience it later (class 1) in both the unadjusted and adjusted models. (p.79)

Table 3.1: Risk ratio of log-binomial regressions of classes on HIV, unadjusted, adjusted for age at enrolment and length of enrolment and adjusted for these and other covariates including study arm

Left event

Model

Variable

Risk ratio

P-value

95%

CI

Left school

Unadjusted

left school class 1

2.894

0.001

1.577

5.309

(N = 2,374)

Adjusted: age at entry,

left school class 1

4.275

0.000

2.313

7.900

time enrolled

age

1.272

0.000

1.187

1.364

enrolled_len

1.170

0.030

1.015

1.348

Adjusted:

left school class 1

2.799

0.009

1.297

6.037

(p.77) age

1.208

0.000

1.114

1.309

enrolled_len

1.218

0.014

1.040

1.426

arm

0.996

0.979

0.765

1.299

attendance

0.991

0.012

0.985

0.998

anxiety

1.039

0.092

0.994

1.085

depression

1.055

0.041

1.002

1.110

parental monitor

0.997

0.920

0.936

1.062

HIV knowledge

1.054

0.738

0.776

1.432

Sexual debut

Unadjusted:

debut class 1

1.141

0.720

0.554

2.349

(N = 2,482)

debut class 2

1.498

0.305

0.693

3.238

Adjusted: age at entry,

debut class 1

2.077

0.051

0.996

4.328

time enrolled

debut class 2

2.781

0.010

1.276

6.058

age

1.277

0.000

1.192

1.369

enrolled_len

1.178

0.024

1.022

1.359

Adjusted:

debut class 1

2.093

0.094

0.882

4.970

debut class 2

2.462

0.054

0.986

6.148

age

1.196

0.000

1.109

1.289

enrolled_len

1.205

0.014

1.039

1.396

arm

1.033

0.793

0.810

1.318

attendance

0.991

0.001

0.985

0.996

anxiety

1.035

0.095

0.994

1.078

depression

1.051

0.036

1.003

1.101

IPV

1.058

0.710

0.785

1.428

HIV knowledge

1.040

0.791

0.781

1.384

Pregnancy

Unadjusted:

pregnancy class 1

0.764

0.185

0.513

1.138

(N = 2,447)

pregnancy class 3

1.580

0.183

0.806

3.097

(p.78) Adjusted: age at entry,

pregnancy class 1

1.633

0.042

1.017

2.623

time enrolled

pregnancy class 3

2.832

0.007

1.336

6.006

age

1.298

0.000

1.199

1.404

enrolled_len

1.202

0.019

1.031

1.403

Adjusted:

pregnancy class 1

1.525

0.062

0.979

2.377

pregnancy class 3

2.026

0.040

1.034

3.971

age

1.238

0.000

1.148

1.335

enrolled_len

1.192

0.020

1.028

1.382

arm

1.024

0.852

0.802

1.307

anxiety

1.040

0.062

0.998

1.083

depression

1.057

0.018

1.010

1.107

IPV

1.150

0.349

0.859

1.539

HIV knowledge

1.017

0.910

0.766

1.350

Parent death

Unadjusted:

parent death class 2

2.030

0.000

1.602

2.574

(N = 2,071)

Adjusted: age at entry,

parent death class 2

1.994

0.000

1.563

2.543

time enrolled

age

1.252

0.000

1.170

1.339

enrolled_len

1.145

0.055

0.997

1.316

Adjusted:

parent death class 2

1.865

0.000

1.460

2.383

age

1.201

0.000

1.119

1.290

enrolled_len

1.155

0.049

1.001

1.333

arm

1.003

0.978

0.787

1.280

anxiety

1.036

0.080

0.996

1.078

depression

1.061

0.012

1.013

1.110

Note: In each case the reference class is the class of the lowest probability of the event.

Early Life Transitions Increase the Risk for HIV Infection: Using Latent Class Growth Models to Assess the Effect of Key Life Events on HIV Incidence Among Adolescent Girls in Rural South Africa

Figure 3.2: Latent class growth analysis trajectories for the four-class model of cumulative life events, where the events included are sexual debut, pregnancy, leaving school and death of a parent

Source: Author’s own

Generaly, across all of the life events, the effect of adjusting for the study arm was not significant.

Cumulative life events and HIV incidence

Figure 3.2 shows the four-class model that was selected to describe the pattern of cumulative life events. Table 3.2 shows the characteristics of each of the cumulative life event classes; class 1 (‘Blue’) had no one who experienced coital debut, pregnancy or school leaving by age 15 and had a relatively low percentage of participants who experienced the death of a parent by age 23 (14% compared to 80–91%). Class 4 (‘Red’) experienced the most negative life events by age 14. The vast majority (88.6%) had debuted by age 14, 21% had experienced a pregnancy by age 14, 90% had experienced parental death by age 14 and 3.5% had left school. Class 2 (‘Green’) and 3 (‘Pink’) started out with a similar number of events by age 14 (more than class 1 and less than class 4), however the gradient of the trajectory for class 3 is steeper than class 2, resulting in a higher number of negative events experienced by age 23. By age 23 class 3 had caught up to class 4 in (p.80) terms of number of negative life events experienced on average, while class 2, although starting in a similar place to class 3 at age 14, had experienced the fewest negative events of any class by age 23.

Table 3.2: Frequency of attributes by class from the model of cumulative life events

Class 1

Class 2

Class 3

Class 4

N

%

N

%

N

%

N

%

HIV

Negative

974

91.1

270

89.7

408

87.9

97

85.1

Positive

95

8.9

31

10.3

56

12.1

17

14.9

Sexual debut by 14

No

1,069

100.0

243

80.7

390

84.1

13

11.4

Yes

0

0.0

58

19.3

74

15.9

101

88.6

Missing

0

0.0

0

0.0

0

0.0

0

0.0

Sexual debut by 17

No

481

45.0

234

77.7

45

9.7

3

2.6

Yes

441

41.3

67

22.3

331

71.3

110

96.5

Missing

147

13.8

0

0.0

88

19.0

1

0.9

Sexual debut by 21

No

37

3.5

22

7.3

2

0.4

1

0.9

Yes

590

55.2

108

35.9

350

75.4

110

96.5

Missing

442

41.3

171

56.8

112

24.1

3

2.6

Sexual debut by 23

No

3

0.3

3

1.0

0

0.0

0

0.0

Yes

594

55.6

109

36.2

351

75.6

110

96.5

Missing

472

44.2

189

62.8

113

24.4

4

3.5

Pregnant by 14

No

1,069

100.0

299

99.3

449

96.8

90

78.9

Yes

0

0.0

2

0.7

15

3.2

24

21.1

Missing

0

0.0

0

0.0

0

0.0

0

0.0

(p.81) Pregnant by 17

No

783

73.2

297

98.7

225

48.5

37

32.5

Yes

127

11.9

4

1.3

124

26.7

59

51.8

Missing

159

14.9

0

0.0

115

24.8

18

15.8

Pregnant by 21

No

95

8.9

39

13.0

15

3.2

3

2.6

Yes

263

24.6

33

11.0

191

41.2

69

60.5

Missing

711

66.5

229

76.1

258

55.6

42

36.8

Pregnant by 23

No

15

1.4

7

2.3

3

0.6

2

1.8

Yes

272

25.4

35

11.6

193

41.6

70

61.4

Missing

782

73.2

259

86.0

268

57.8

42

36.8

Left school by 14

No

1,069

100.0

301

100.0

464

100.0

110

96.5

Yes

0

0.0

0

0.0

0

0.0

4

3.5

Missing

0

0.0

0

0.0

0

0.0

0

0.0

Left school by 17

No

870

81.4

301

100.0

306

65.9

75

65.8

Yes

26

2.4

0

0.0

29

6.3

15

13.2

Missing

173

16.2

0

0.0

129

27.8

24

21.1

Left school by 21

No

84

7.9

32

10.6

35

7.5

6

5.3

Yes

257

24.0

50

16.6

125

26.9

38

33.3

Missing

728

68.1

219

72.8

304

65.5

70

61.4

(p.82) Left school by 23

No

8

0.7

2

0.7

2

0.4

0

0.0

Yes

296

27.7

64

21.3

140

30.2

39

34.2

Missing

765

71.6

235

78.1

322

69.4

75

65.8

Parent death by 14

No

805

75.3

46

15.3

66

14.2

8

7.0

Yes

0

0.0

241

80.1

375

80.8

103

90.4

Missing

264

24.7

14

4.7

23

5.0

3

2.6

Parent death by 17

No

502

47.0

46

15.3

31

6.7

5

4.4

Yes

97

9.1

241

80.1

383

82.5

103

90.4

Missing

470

44.0

14

4.7

50

10.8

6

5.3

Parent death by 21

No

62

5.8

6

2.0

3

0.6

0

0.0

Yes

150

14.0

243

80.7

384

82.8

104

91.2

Missing

857

80.2

52

17.3

77

16.6

10

8.8

Parent death by 23

No

6

0.6

0

0.0

0

0.0

0

0.0

Yes

152

14.2

243

80.7

384

82.8

104

91.2

Missing

911

85.2

58

19.3

80

17.2

10

8.8

(p.83)

Table 3.3: Risk ratios of HIV and the cumulative life event trajectories illustrated in Figure 3.2 both unadjusted and adjusted for age at enrolment and length of enrolment

Risk ratio – unadjusted

Colour

Class

Risk ratio

Std. Err.

p-value

95% CI

Blue

1-Reference

1.00

Green

2

1.16

0.227

0.45

0.79

1.70

Pink

3

1.36

0.216

0.05

0.99

1.86

Red

4

1.68

0.410

0.03

1.04

2.71

Risk ratio – adjusted for age at enrolment and length of enrolment

Colour

Class

Risk ratio

Std. Err.

p-value

95% CI

Blue

1-Reference

1.00

Green

2

1.11

0.22

0.59

0.76

1.63

Pink

3

1.44

0.23

0.02

1.06

1.96

Red

4

1.81

0.44

0.01

1.13

2.90

We then examined the risk of HIV acquisition by class. Compared to class 1, the class with the fewest events by age 14, all other classes had an increased risk of HIV infection although only class 3 and 4 have a significantly increased risk of infection (Table 3.3). While class 3 and 4 experienced the same number of negative life events by age 23, class 4, the group that experienced the most negative events by age 14, had a greater risk of HIV acquisition (RR 1.81 95% CI 1.31, 2.89) than class 3 (RR 1.44, 95% CI 1.06, 1.96). Even in class 2, where by age 23 the participants have experienced fewer events than those in class 1, the risk of HIV infection is higher, though the difference is not statistically significant. This suggests that there could be an increased impact of these life events when they occur earlier in the participants’ lives as compared to later.

Dominance analysis ranked pregnancy as the most important of the life events in increasing risk of HIV infection, followed by leaving school, while sexual debut was third (Table 3.4). The death of a parent was ranked fourth of these life events.

(p.84) Table 3.4: Dominance analysis of life events on risk of HIV infection

Life event

Dominance statistic

Standardized dominance statistic

Ranking

Pregnancy

0.0197

0.3185

1

Leaving school

0.0185

0.2992

2

Sexual debut

0.0173

0.2786

3

Parent death

0.0064

0.1037

4

Conclusions

It was found that adolescent girls who experienced key life events before the age of 15, specifically pregnancy, coital debut, leaving school and parental death, were at increased risk of HIV infection. Using latent growth class analysis, adolescent girls who experienced more life events before the age of 15 had the highest risk of HIV acquisition by the age of 23. Those who experienced the same number of life events by age 23 were also at increased risk of HIV but not at as great a risk as the group with the most events that occurred in early adolescence. Interestingly, the class who by age 23 had the fewest events but more life events occurring in early adolescence than the other classes also had an increased risk of HIV infection compared to the group with more events later in adolescence, although the difference was not statistically significant.

These results add to the evidence base that timing of events in the adolescent life course, not just the occurrence of the events, impact the risk of HIV acquisition and that these events have not just short-term impacts on increasing risk but long-term effects well into early adulthood. All of the events examined are part of the natural transition from adolescence into adulthood; however, when these events happen early in adolescence they may place adolescents at increased risk. All of the life events examined have been found independently to be associated with HIV infection, but few studies are longitudinal so that the evidence of these events being associated with an increased risk of future infection is limited. Importantly this work demonstrates that it is not just the occurrence of a life event or the number of life events that a young person experiences that shapes HIV risk but when they occur in the life course. This work highlights that earlier life events play (p.85) a particularly important role in HIV risk over the years of transition into adulthood.

There are many pathways through which early negative life events could lead to increased HIV risk. It is likely there are direct risks for HIV associated with these exposures, such as sexual behaviour, but also other more distal risk factors such as mental health and environmental stressors that likely place young people who experience these events as they transition to adulthood at greater risk. In this analysis, both early coital debut and early pregnancy indicate early initiation of sexual behaviour, meaning adolescent girls have more time when they are at risk for HIV exposure. However, even after adjusting for time, early debut and pregnancy increase risk of HIV acquisition, suggesting that other mechanisms may be increasing risk such as older partners or unprotected sex. Earlier work in this cohort has found that low school attendance and leaving school increase HIV risk and that this risk is explained by older partners and more sexual partners.(Stoner et al, 2017, 2018). Thus school provides a protective environment from HIV infection. Loss of a parent may also lead to increased risk through similar pathways such as lack of parental monitoring and parental care and supervision (Operario et al, 2011).

There is a growing recognition of the importance of childhood and early adolescence on shaping future health. There is a large body of literature demonstrating that adverse childhood events have many negative health outcomes, including increased adult mortality, chronic disease, mental health and sexual behaviour (Hughes et al, 2017; Boullier and Blair, 2018; Balistreri and Alvira-Hammond, 2016). However, much of the work on ACEs is retrospective, asking adults about negative life events that happened before the age of 18 (including, for example, abuse, neglect, death of a parent, living in a negative household/environment). Thus, these measures often do not allow for the examination of how when these events occurred in an adolescent’s life impacted future risk. There is a growing body of literature documenting early adolescence as an important time in life where negative events can have a significant impact on later life (Evans et al, 2013), but it is also a time for opportunity to intervene to counter negative future outcomes (Fuhrmann et al, 2015). While negative experiences during early adolescence can set up negative patterns of behaviour that continue into adulthood, it also provides an opportunity to intervene to prevent these risky trajectories from continuing (UNICEF, 2017). In addition, the life events measured do not occur in isolation but within a larger environment that adolescents and their caregivers operate in; cultural expectations and the social (p.86) consequences of life events may have differential impacts for youth in different settings (UNICEF, 2017). Further, events such as early coital debut, pregnancy and leaving school are associated, and one event may lead to an adolescent experiencing another (for example, pregnancy leads to leaving school) which is consistent with life course theory. Thus, identifying these events when they happen and intervening early with supportive, evidence-based interventions so that more events do not occur is important.

The implications of these findings are that HIV prevention programmes need to not only screen for current risk factors but take into account earlier life events that may place adolescents on a trajectory of increased risk into adulthood and perhaps beyond that. Successfully meeting SDG goal 3.1, ending the HIV epidemic by 2030, will require a holistic view of prevention over the life course and understanding that events that happen to individuals earlier in their lives impact their future HIV risk. While HIV incidence does not increase rapidly until after age 18, experiences that happen in early adolescence and even childhood put young women at increased risk well into early adulthood. A two-fold approach to HIV prevention programming and policy in adolescents involves both intervening with younger adolescents to prevent negative early life events, working with young adolescents experiencing negative life events to prevent future negative health outcomes and also working with older adolescents who have also experienced negative life events to address trauma, coping and resilience skills to support prevention behaviours. In particular, programmes and policies that support young women staying in secondary school and completing school and those providing comprehensive, adolescent health services to prevent early pregnancies and comprehensive sexuality education in schools are some of the key steps that may help provide safety nets to help adolescents transition safely to adulthood.

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