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ALSPAC Data

Measures of Childhood Incontinence

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Or, if you’re squeamish…

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How many kittens do you own?

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Repeated questions:

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Repeated questions: - Binary

Zero One

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Repeated questions: - Ordinal

Zero One Two ~ DSM4 criterion

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Repeated questions

• Asked at:

• 4½ years ~ KK• 5½ years ~ KM• 6½ years ~ KP• 7½ years ~ KR • 9½ years ~ KU

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Why mixture models?

• Previous work (clinical/epidemiological) has provided evidence for subgroups– Different aetilogies– Different comorbid factors– Different long-term outcomes

• Variability in development poorly captured by standard growth models– Relapsing group

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BW frequencies (complete case)Boys Girls

4.5yr

Dry 62% 77%

“Infrequent” 27%38%

17%23%

“Frequent” 11% 6%

5.5yr

Dry 72% 84%

“Infrequent” 21%28%

13%16%

“Frequent” 7% 3%

6.5yr

Dry 76% 87%

“Infrequent” 20%24%

11%14%

“Frequent” 5% 2%

7.5yr

Dry 81% 90%

“Infrequent” 16%19%

9%10%

“Frequent” 3% 1%

9.5yr

Dry 87% 94%

“Infrequent” 11%13%

5%6%

“Frequent” 2% 1%

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Infrequent bedwetting

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Frequent Bedwetting

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Planned models

• LLCA replication of Croudace AJE model– Incorporate covariates into above

• LLCA/LCGA models of frequent wetters (binary)– Assessment of gender invariance with knownclass

• Parallel modelling of day/night wetting• Ordinal modelling of 3-level measures

– Incorporate covariates– Risk of later binary outcome