A job exposure matrix for physical load dutch experiences
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A job exposure matrix for physical load: Dutch experiences. Lex Burdorf Department of Public Health University Medical Center Rotterdam. When to consider a job exposure matrix ?. JEM as only possibility: - no information on physical load available at individual level

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A job exposure matrix for physical load dutch experiences

A job exposure matrix for physical load:Dutch experiences

Lex Burdorf

Department of Public Health

University Medical Center Rotterdam


When to consider a job exposure matrix
When to consider a job exposure matrix ?

JEM as only possibility:

- no information on physical load available at individual level

- jobs have distinct exposure profiles with combined exposure to several determinants of physical load

JEM to be considered:

- assessment at individual level with large within-worker variance

(classical vs Berkson's error)

- historical trends


Description of jobs
Description of jobs

Hierarchy in questions on occupational job title:

- what is your job ? (generic description)

- in which company / industry do your work ? (generic description)

- what are your daily activities ? (generic description)

Hierarchy in data collection on occupational job titles:

General questionnaire:

1. What is your job ?

2. Which branch of industry ?

Job-specific questionnaire:

3. Frequency and duration of specific activities within jobs ?

Tielemans et al Occup Environ Med 1999;56:145-51.


What is your job
What is your job ?

Problems:

* Too generic description, eg top 10 jobs in community-based study among pregnant women in Rotterdam 2004-2006

* description not specific enough, e.g. nurse, agricultural worker


Job description among women
Job description among women

Top 10:

administrative employee 389 8.0%

teacher 172 3.5%

nursery, kindergarten worker 153 3.1%

shop assistent 141 2.9%

secretary 139 2.9%

lawyer, barrister 139 2.9%

physician 123 2.5%

cleaner 123 2.5%

nurse 108 2.2%

cashier 87 1.8%

1574 32.3%


What is your job1
What is your job ?

Problems:

* Too generic description, eg top 10 jobs in community-based study among pregnant women in Rotterdam 2004-2006

* description not specific enough, e.g. nurse, agricultural worker

* 'interesting' descriptions, eg sandwich-designer, visual presenter

Experiences:

* problems larger among jobs in industry (eg operator)

* large variability within job titles in self-reported exposure to determinants of physical load


What is your job2
What is your job ?

Problems:

* large variability within job titles in self-reported exposure to determinants of physical load (4 point scales)

Nursery / kindergarten worker:

often / always

Standing 38%

Sitting 85%

MMH > 5 kg 50%

MMH > 25 kg 6%

- variation within job ?

- question not valid ?

- interpretation: average exposure within job ?


Which company industry do your work
Which company / industry do your work ?

Problems:

* company name is not always very informative (e.g large companies)

* description not specific enough, e.g. government

Experiences:

* nurse in hospital is not informative without knowing the specific department and specific activities


What are your daily activities
What are your daily activities ?

Problems:

* no information on frequency and duration

* no standardized description possible, hence, sometimes difficult to interpret

Experiences:

* cannot be linked to exposure pattern, useful additional information for job classification


Classification of occupational job titles
Classification of occupational job titles

Coding systems:

- current classification; education, job, activities, competencies

5 digits, first digit 5 classes, 3 digits job group, 5 digits job title

- old classification; jobs within specific industries

4 digits, 2 digits branch of industry, 4 digits job title

Problems:

* current classification: very useful for SES, but job titles with completely different exposure profiles into similar codes

* old classification: not useful for modern jobs (e.g ICT is completely lacking) or jobs with strong development (eg order picker in warehouse)

* do not underestimate inter-observer agreement !


How well is the classification of occupational job titles
How well is the classification of occupational job titles ?

Study population with 37 occupational OJT (each at least 30 subjects)

Self-reported physical load: often to always

standing 23%

sitting 50%

walking 18%

manual materials handling > 5 kg 14%

manual materials handling > 25 kg 2.1%

driving vehicles > 4 hrs 1.4%


How well is the classification of occupational job titles1
How well is the classification of occupational job titles ?

Study population (n > 3000) with 37 OJT (each at least 30 subjects)

Physical load prevalence explained variance by OJT

standing 23% 28%

sitting 50% 38%

walking 18% 18%

mmh > 5 kg 14% 12%

mmh > 25 kg 2.1% 7.8%

driving > 4 hrs 1.4% 2.9%


How well is the classification of occupational job titles2
How well is the classification of occupational job titles ?

Study population with 17 occupational job groups, comparable OJT collated into groups (hierachical taxonomy, 5 digits into 3 digit group)

Physical load explained variance

by OJT by OTG

standing 28% 14%

sitting 38% 27%

walking 18% 11%

mmh > 5 kg 12% 8.1%

mmh > 25 kg 7.8% 7.0%

driving > 4 hrs 2.9% 1.3%


How well is the classification of occupational job titles3
How well is the classification of occupational job titles ?

Conclusion:

- JEM performance partly determined by between-worker (=within- group) and between-job variance, post hoc evaluation needed to determine optimum grouping strategy

- how specific should the OJT be ?

5 digit level requires more information, hampers comparability

- explained variance very low with low prevalence of exposure

(specificity is crucial factor)


Internal versus external jem
Internal versus external JEM

Internal JEM:

- information on distribution of exposure within the study population

- artificial reduction of between-worker variance (zero within job)

- available exposure data usually limited, hence, less precision

External JEM:

- information on distribution of exposure from external population or based upon expert judgement

- generalisibility to other populations ?


Some classical issues
Some classical issues

Job-exposure matrix:

- level of detail of exposure characterisation (eg 'possible' (lenient) and 'probable' (strict))

- performance relative to exposure prevalence:

* low prevalence, specificity is more important

* high prevalence, sensitivity becomes more important

- JEM vs individual assessment

* JEM less recall bias or no bias at all (blinded)

* classical vs Berkson's error (ind vs grouping)

* optimum grouping strategy


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