Occupation Asthma: HOW OFTEN Paul Blanc M.D. M.S.P.H. Division of Occupational and Environmental Medicine University of California San Francisco, USA

Focus of Discussion 3Epidemiological perspective 3Population attributable risk (PAR%) 3Asthma associated with grouped occupations or with globally-defined occupational exposures

An Substantive Proportion of Asthma Among Adults is Attributable to Occupation

Data How Much Adult Asthma Can Be Attributed to Occupational Factors [PD Blanc, K Toren; Am J Med 1999; 107:580-87]

Methods of Review Medline search with cross check of citations Use of published PAR% is presented Calculation of PAR% if not presented: allowed [P exp x (RR-1)/ [P exp x (RR-1)] +1 If incidence of occupational asthma alone: occupational incidence/general incidence [fixed at 1 per 1000 per year] Weighted scoring of study quality

PAR% from Published Estimates 23 Published Estimates, Data from 17 Countries [Canada 3, USA 8, UK 2, Spain 2; Nordic 3; Asia 2, Africa 1; ECRHS 1 PAR% range: % Median PAR 9% - Mean PAR 12%

PAR% Calculated from Studies 8 published OR or RR, Data from 7 countries [6 European; 1 China] PAR% range: % Median PAR 25% - Mean PAR 26%

PAR% Extrapolated from Incidence 12 incidence estimates, Data from 6 countries [15 reports; 2 analyses from 3 systems averaged] PAR% range: % Median PAR 5%

Summary Data

Range of EstimatesPAR% Low end2 - 6% High end % Most common findings9 -15% Another Way of Putting It

2003 ATS Statement on the Occupational Contribution to the Burden of Airway Disease Publications through 1999 Published PAR% cited if present PAR% calculated as Control exp (RR-1)/RR

ATS Analysis 21 Studies Analyzed Includes Several Studies not Previously Used PAR% Range % Median value = 15%

Recent Incidence Data

What About “Pure” Occupational Asthma Registry and Other Incidence Data? LocationRate per 100,000 France (96-99)2.4 Finland (89-95)17.4 South Africa (96-98)1.2 (3.8 Cape) Sweden (90-92)8.0 UK (89-91)

What About the Attributable Risk of Work Aggravated Asthma? Work aggravation of asthma is common Usually not analyzed by job type Should not be left out of the equation

Studies of the Work Impact of Asthma: Adults of Working Age - International Study Location (author,year) N Study findings Finland (Saarinen, 2003) % work aggravated symptoms (5% daily) Switz. (Schwenkglenks, 2003) % work absence (year) Sweden (Balder,1998) %  job; 4%  duties Australia (Abramson, 1995) 159 5% quit work New Zealand (McClellan,1990) 821 7% work choice limited USA (Arif, 2002) % asthma worse on job UK (Sibbald, 1991) 460 3% long term sick leave Singapore (Goh, 1994) % >1 week absence/yr

Study Workplace ETS RR (95% CI) 7th Day AdventistAll subjects 1.45 ( ) Men 1.5 ( ) Women 1.5 ( ) What About Environmental Tobacco Smoke? Risk expressed per 10 years of exposure At 35% population exposure this would yield a PAR% of 14.9%

Theoretical Model: Adult Asthma Prevalence and Population Attributable Risk %

Issues to Consider Effect of defining exposure on our PAR% estimates [self report, occupation, JEM] Defining “adult onset” asthma PAR% methodologies and interpretation Occupational PAR% for other airways diseases

Summary 3Occupational asthma PAR% is at least 10% and probably closer to 15% 3This does not include work aggravated asthma 3“Pure” occupational asthma incidence data may be useful for trends but not for general public health estimates