Risks of future harm in adolescents hospitalised with violent, self-inflicted or drug/alcohol-related

453 Pages·2016·15.63 MB·English

by  Annie Herbert

Risks of future harm in adolescents hospitalised with
violent, self-inflicted or drug/alcohol-related injury

Anne Herbert

A thesis submitted for the degree of
Doctor of Philosophy

Population, Policy & Practice Programme
Institute of Child Health
Faculty of Population Health Sciences
University College London (UCL)

November 2016
Declaration
I, Annie Herbert, confirm that the work presented in this thesis is my own.
Where information has been derived from other sources, I confirm that this has
been indicated in the thesis.
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Abstract
Background: Information is lacking on the risks of future harm for adolescents
hospitalised in England as an emergency with adversity-related injury (violent,
self-inflicted, drug/alcohol-related). Evidence is needed on who is most at risk
and the types of harm, to inform preventive strategies.
Methods: Using Hospital Episode Statistics linked to Office for National
Statistics mortality data for England (April 1997-March 2012), I estimated the
prevalence of emergency admissions for adversity-related injury among 10-
19y olds, and identified risk factors. I examined the risks of death and
emergency re-admission after discharge from adversity-related injury,
compared with after accident-related injury.
Results: 1 in 25 adolescents had an emergency admission for adversity-
related injury between the ages of 10 and 19y. Among these adolescents, 73%
of girls and 38% of boys were admitted with more than one type (e.g., self-
inflicted and drug/alcohol-related). In addition, 1/137 girls and 1/64 boys with
adversity-related injury died within ten years after discharge; 54% of girls and
41% of boys were re-admitted as an emergency. These risks were
approximately double those following accident-related injury, regardless of
whether violent, self-inflicted or drug/alcohol-related, and were particularly high
for older boys and adolescents with chronic conditions. Increased risks of
death were mostly explained by suicide and drug/alcohol-related deaths. After
each type of adversity-related injury, risks of drug/alcohol-related deaths were
similar to those of suicide deaths.
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Conclusions: 1 in 25 adolescents in England were admitted as an emergency
to hospital for adversity-related injury, often with multiple types of adversity-
related injury, and were at considerable risks of harm in the next decade
compared to other adolescents. Current strategies to reduce risks after self-
inflicted injury in this group should be extended to violent and drug/alcohol-
related injury. Strategies could include targeting older adolescents with chronic
conditions, and prioritising risks of drug/alcohol-related death alongside those
of suicide death.
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Contents
Declaration................................................................................................................... 2
Abstract ........................................................................................................................ 3
Contents ....................................................................................................................... 5
Tables ......................................................................................................................... 13
Figures........................................................................................................................ 17
Abbreviations............................................................................................................. 22
Notation ...................................................................................................................... 23
Statement about funders ......................................................................................... 24
Acknowledgements .................................................................................................. 25
Chapter 1 Thesis background and rationale ..................................................... 26
1.1 Chapter summary ...................................................................................... 26
1.2 Introduction ................................................................................................. 28
1.3 Importance of adversity-related injury among adolescents ................ 28
1.3.1 Why adolescents? .............................................................................. 28
1.3.2 Why violent, self-inflicted and drug/alcohol-related injury?.......... 31
1.3.3 Defining violent, self-inflicted and drug/alcohol-related injury ..... 35
1.3.4 Why emergency presentations to hospital? ................................... 40
1.4 Prevalence of presentations to hospital for adversity among
adolescents in England ....................................................................................... 43
1.4.1 What is known ..................................................................................... 43
1.4.2 Gaps in the evidence ......................................................................... 47
1.4.3 Implications for clinical guidelines.................................................... 50
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1.5 Risks of future harm following a presentation to hospital for adversity:
a systematic review .............................................................................................. 55
1.5.1 Introduction .......................................................................................... 55
1.5.2 Methods................................................................................................ 56
1.5.3 Results.................................................................................................. 59
1.5.4 Discussion............................................................................................ 71
1.6 Effectiveness of psychosocial interventions for reducing future harm:
an overview of systematic reviews .................................................................... 74
1.6.1 Introduction .......................................................................................... 74
1.6.2 Methods................................................................................................ 74
1.6.3 Results.................................................................................................. 77
1.6.4 Discussion............................................................................................ 98
1.7 Conclusions of Chapter 1 ....................................................................... 101
Chapter 2 Thesis aim, objectives, hypotheses, and further chapters ......... 103
Chapter 3 Data sources ..................................................................................... 106
3.1 Chapter summary .................................................................................... 106
3.2 Introduction ............................................................................................... 107
3.3 Hospital Episode Statistics inpatient data linked to Office for National
Statistics mortality data (HES-ONS)................................................................ 107
3.3.1 Background........................................................................................ 107
3.3.2 Data processing and linkage .......................................................... 108
3.3.3 Episodes, admissions and diagnoses in HES data..................... 115
3.3.4 Causes of death................................................................................ 116
3.3.5 Data extract for this thesis............................................................... 118
3.3.6 Strengths and limitations of HES-ONS for this thesis................. 131
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3.4 Office for National Statistics (ONS) population mid-year estimates 137
3.4.1 Background........................................................................................ 137
3.4.2 Data processing ................................................................................ 137
3.4.3 Data extract for this thesis............................................................... 137
3.4.4 Strengths and limitations of ONS mid-year estimates for this thesis
138
Chapter 4 Study I, Prevalence of emergency admissions for adversity-related
injury (Objectives 1 and 2) .................................................................................... 140
4.1 Chapter summary .................................................................................... 140
4.2 Introduction ............................................................................................... 142
4.3 Methods ..................................................................................................... 143
4.3.1 Study cohort and admissions ......................................................... 143
4.3.2 Adolescent groups............................................................................ 143
4.3.3 Adolescent characteristics .............................................................. 146
4.3.4 Population denominators................................................................. 146
4.3.5 Statistical analyses ........................................................................... 146
4.4 Results ....................................................................................................... 150
4.4.1 Objective 1: Prevalence of adversity-related injury ..................... 150
4.4.2 Objective 2: Proportions of adolescents with violent, self-inflicted,
and drug/alcohol-related injury ..................................................................... 164
4.4.3 Sensitivity analyses .......................................................................... 171
4.5 Discussion ................................................................................................. 171
4.5.1 Strengths and limitations ................................................................. 172
4.5.2 Comparisons with other studies ..................................................... 174
4.5.3 Implications of findings .................................................................... 175
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Chapter 5 Statistical methods for estimating risks of harm following
admissions for adversity-related and accident-related injury .......................... 177
5.1 Chapter summary .................................................................................... 177
5.2 Introduction ............................................................................................... 179
5.3 Why time-to-event methods? ................................................................. 182
5.4 Methods for estimating risks of future harm (Objective 3) ................ 183
5.4.1 The cumulative failure function and other related functions ...... 184
5.4.2 Kaplan-Meier, Life-table, and Nelson-Aalen estimates .............. 187
5.5 Methods for comparing risks of harm following adversity-related injury
with those following accident-related injury (Objective 4) ............................ 189
5.5.1 Semi-parametric proportional hazards models ............................ 192
5.5.2 Model assumptions of the semi-parametric PH model ............... 193
5.5.3 Alternative methods.......................................................................... 204
5.6 Methods for estimating cause-specific risks of death (Objective 5) 210
5.6.1 Cumulative incidence functions and Fine & Gray’s sub-hazard
models 211
5.6.2 Alternative methods.......................................................................... 215
5.7 Issue 1: Clustering of index emergency admissions for injury ......... 216
5.7.1 The problem ...................................................................................... 216
5.7.2 Randomly selecting an index admission....................................... 218
5.7.3 Alternative methods.......................................................................... 219
5.8 Issue 2: Recurrent events....................................................................... 224
5.8.1 The problem ...................................................................................... 224
5.8.2 Wei, Lin & Weissfeld (WLW) and Prentice, Williams & Peterson
(PWP) gap-time approaches to modelling recurrent events.................... 227
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5.7.4 Alternative methods.......................................................................... 234
5.9 Goodness-of-fit ......................................................................................... 237
5.10 Discussion ................................................................................................. 239
Chapter 6 Study II, Risks of death and emergency re-admissions following
adversity-related injury (Objectives 3 and 4)...................................................... 242
6.1 Chapter summary .................................................................................... 242
6.2 Introduction ............................................................................................... 244
6.3 Methods ..................................................................................................... 244
6.3.3 Study cohort and admissions ......................................................... 244
6.3.4 Adolescent groups............................................................................ 247
6.3.5 Outcomes........................................................................................... 249
6.3.6 Confounding and independent variables ...................................... 249
6.3.7 Statistical analyses ........................................................................... 249
6.4 Results ....................................................................................................... 252
6.4.1 Objective 3: Absolute risks of death and emergency re-admission
258
6.4.2 Objective 4: Outcomes following adversity-related injury (versus
accident-related injury) .................................................................................. 259
6.5 Discussion ................................................................................................. 274
6.5.1 Strengths and limitations ................................................................. 275
6.5.2 Comparisons with other studies ..................................................... 276
6.5.3 Implications of findings .................................................................... 277
Chapter 7 Study III, Pathways from adversity-related injury to increased risks
of death (Objective 5)............................................................................................. 279
7.1 Chapter summary .................................................................................... 279
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7.2 Introduction ............................................................................................... 281
7.3 Methods ..................................................................................................... 282
7.3.1 Study cohort ...................................................................................... 282
7.3.2 Exposures and other characteristics ............................................. 282
7.3.3 Outcome measures .......................................................................... 283
7.3.4 Statistical analyses ........................................................................... 284
7.4 Results ....................................................................................................... 285
7.4.1 Objective 5: Risks of cause-specific deaths following adversity-
related and accident-related injury............................................................... 289
7.5 Discussion ................................................................................................. 295
7.5.1 Strengths and limitations ................................................................. 295
7.5.2 Comparisons with other studies ..................................................... 296
7.5.3 Implications of findings .................................................................... 297
Chapter 8 Synthesis of thesis findings............................................................. 299
8.1 Chapter summary .................................................................................... 299
8.2 Introduction ............................................................................................... 300
8.3 What this thesis adds to the literature .................................................. 300
8.4 Limitations of this thesis and further research .................................... 302
8.5 Implications for policy and practice ....................................................... 304
8.6 Concluding remarks................................................................................. 307
Appendices .............................................................................................................. 308
A. Systematic review of studies reporting risks of harm following an
admission for adversity-related injury.............................................................. 308
A.1 Search terms ............................................................................................ 308
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