Pubertal timing and tempo in urban South Africa – associations with health in adolescence and transitions to adulthood Public
Kowalski, Alysse (Spring 2020)
Published
Abstract
While a universal process, there is substantial interindividual variation in the timing and tempo of puberty. Previous research from high-income countries (HICs) suggests pubertal timing and tempo are associated with adolescent mental health, health risk behavior activity, and pregnancy. As puberty takes place during secondary school, its timing and tempo have also been shown to be associated with schooling performance and completion which have important implications for overall schooling attainment and economic opportunities, though evidence of these associations is limited. Little is known about associations with pubertal timing and tempo in low- and middle-income countries (LMICs) which tend to have higher levels of poverty and environmental stress. The overarching goal of this dissertation was to investigate associations of pubertal timing and tempo with adolescent mental health, risk behavior initiation, and pregnancy and schooling and employment in early adulthood in urban South Africa.
This research used 10+ waves of data from the Birth to Twenty Plus cohort, an observational birth cohort in Soweto-Johannesburg established in 1990. First, using data on adolescent smoking, alcohol, cannabis, illicit drug, and sexual activity initiation, we conducted cluster analyses to identify patterns of health risk behavior initiation. Second, we examined associations of pubertal timing and tempo (genital/breast development class, pubic hair development class, age at menarche) with adolescent emotional and behavioral problems, eating attitudes, and health risk behavior initiation patterns using multinomial and linear regression as appropriate, and examined the consistency of these associations by levels of childhood stress. Third, we used generalized structural equation models to examine associations of pubertal timing and tempo with ordinal measures of schooling attainment and employment status at age 22 y and explored the mediating role of adolescent health risk behavior initiation pattern and adolescent pregnancy.
We identified 3 distinct patterns of adolescent health risk behavior initiation for males and females corresponding to low, moderate, and high-risk, such that individuals following the low-risk pattern initiated behaviors at below average rates compared to the sample population while individuals following the high-risk pattern initiated behaviors at above average rates and tended to do so at a younger age. Pubertal timing and tempo were associated with indicators of adolescent mental health and patterns of risk behavior initiation. In general, individuals who matured earlier and faster relative to their peers had increased internalizing and externalizing problems, poorer eating attitudes (females only), and were more likely to follow the moderate and high-risk health risk behavior initiation patterns, while there was a small protective effect for individuals who matured later and slower. These associations did not differ by level of childhood stress. Individuals with relatively later and slower pubertal timing and tempo had poorer schooling attainment at age 22 y, while females who matured earlier and faster had better employment status. Overall associations were not mediated by patterns of adolescent health risk behavior initiation or pregnancy. We postulate these associations may be explained by differences in socioeconomic status that were not adjusted for by our measure of material asset ownership.
These results illustrate similarities in associations of pubertal timing and tempo with adolescent health measures in urban South Africa with those in HICs, suggesting commonalities across settings. Associations of pubertal timing and tempo with young adult schooling attainment and employment may differ between LMICs and HICs.
Table of Contents
Chapter 1: Introduction. 1
Research Aim 1. 2
Research Aim 2. 2
Research Aim 3. 3
References. 4
Chapter 2: Background. 7
Adolescent development 7
Sexual maturation. 8
Pubertal timing and tempo. 9
Drivers of pubertal timing and tempo. 10
Other physical development 11
Cognitive and social and emotional development 11
Associations of pubertal timing and tempo with adolescent outcomes. 12
Mental health. 13
Substance use. 14
Sexual debut and pregnancy. 14
Associations of pubertal timing and tempo with schooling and employment outcomes. 15
Maturity gap. 16
References. 17
Chapter 3: Extended Methods. 27
Birth to Twenty Plus cohort 27
Datasets. 27
Measures of interest 28
Data collection. 29
Pre-puberty measures. 29
Maternal characteristics at enrollment 30
Household asset ownership. 30
Childhood exposure to stress and violence. 30
Childhood fluid intelligence. 31
Height-for-age Z-score (HAZ) 31
Body mass index-for-age Z-score (BMIZ) 31
Two-way imputation (TWI) 31
Adolescent Measures. 32
Pubertal timing and tempo. 32
Age of menarche. 33
Emotional and behavioral adjustment 33
Eating Attitudes. 34
Health risk behaviors. 36
Young Adult Measures. 52
Young adult pregnancy. 52
Categories of schooling attainment 52
Categories of employment 52
Extended Analytical Methods. 53
Research Aim 1. Describe smoking, alcohol, cannabis, illicit drug, and sexual initiation from ages 10 to 18 y, persistence at age 18 y, and patterns of initiation. 53
Research Aim 2. Examine associations of pubertal timing and tempo with measures of adolescent mental health and health risk behavior initiation and examine the consistency of associations by level of childhood stress. 55
Research Aim 3. Examine associations of pubertal timing and tempo with schooling attainment and employment status at age 22 y and explore the mediating role of adolescent health risk behavior initiation and pregnancy. 56
References. 59
Chapter 4: Initiation and persistence of health risk behaviors through adolescence in urban South Africa. 62
Abstract 62
Introduction. 63
Methods. 64
Birth to Twenty Plus (Bt20+) cohort 64
Ethical approval 64
Data collection. 64
Risk behaviors. 65
Adolescent pregnancy. 66
Sociodemographic characteristics. 66
Data management and preparation. 66
Results. 68
Sample characteristics. 68
Cumulative risk behavior initiation by age and stage of adolescence. 68
Current risk behavior engagement at age 18 y and stage of initiation. 68
Cluster analysis and risk behavior profiles. 69
Sensitivity analysis. 69
Discussion. 70
References. 74
Tables and Figures. 78
Supplemental Tables and Figures. 84
Chapter 5: Associations of pubertal timing and tempo with adolescent mental health and health risk behavior initiation: longitudinal findings from the Birth to Twenty Plus cohort 90
Abstract 90
Introduction. 91
Methods. 92
Birth to Twenty Plus (Bt20+) cohort 92
Ethical approval 92
Data collection. 93
Exposures. 93
Outcomes. 93
Covariates. 94
Analytical sample. 94
Two-way imputation. 95
Statistical analysis. 95
Results. 96
Adjusted associations of pubertal development with health risk behavior pattern, emotional and behavioral problems, and eating attitudes among males. 96
Adjusted associations of pubertal development with health risk behavior pattern, emotional and behavioral problems, and eating attitudes among females. 97
Discussion. 98
References. 102
Tables and Figures. 106
Supplemental Tables. 115
Chapter 6: Associations of pubertal timing and tempo with schooling attainment and employment in adulthood in urban South Africa. 120
Abstract 120
Introduction. 121
Methods. 122
Study population. 122
Data collection. 122
Independent variables. 123
Dependent variables. 123
Covariates. 124
Analytical sample. 124
Statistical analysis. 124
Results. 125
SEM results, males. 126
SEM results, females. 126
Discussion. 127
References. 132
Tables and Figures. 135
Supplemental Tables and Figures. 144
Chapter 7: Discussion. 151
Summary of findings. 152
Research Aim 1. Describe smoking, alcohol, cannabis, illicit drug, and sexual initiation from ages 10 to 18 y, persistence at age 18 y, and patterns of initiation. 152
Research Aim 2. Examine associations of pubertal timing and tempo with measures of adolescent mental health and health risk behavior initiation and examine the consistency of associations by level of childhood stress. 153
Research Aim 3. Examine associations of pubertal timing and tempo with schooling attainment and employment status at age 22 y and explore the mediating role of adolescent health risk behavior initiation and pregnancy. 154
Strengths and Limitations. 154
Strengths. 154
Limitations. 155
Life History Theory. 157
Life history theory applied to the Birth to Twenty Plus cohort 159
Future directions. 162
Implications for public health. 162
Implications for research. 164
Conclusions. 166
References. 167
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