Publications

We adapted and tested a previously published questionnaire battery eliciting sensory and cognitive symptoms during (acute) and immediately after (post-acute) GHB intoxication. Studying 125 GHB users, we assessed the instrument's internal consistency using Cronbach's alpha (CA) and responsiveness to change comparing acute and post-acute symptoms. The final 14-item battery demonstrated good internal consistency (CA >or= 0.85, both acute and post-acute). The median symptom score (possible range 0-64) was 30 (acute) and 6 (post-acute; difference p < 0.001). This modified substance-specific symptom battery, which is easily administered, demonstrated excellent performance characteristics. It can be used to study GHB and, potentially, related drugs of abuse.

BACKGROUND

Mortality risk in adult asthma is poorly understood, especially the interplay among race, disease severity, and health care access.

OBJECTIVE

To examine mortality risk factors in adult asthma.

METHODS

In a prospective cohort study of 865 adults with severe asthma in a closed-panel managed care organization, we used structured interviews to evaluate baseline sociodemographics, asthma history, and health status. Patients were followed up until death or the end of the study (mean, 2 years). We used Cox proportional hazards regression to evaluate the impact of sociodemographics, cigarette smoking, and validated measures of perceived asthma control, physical health status, and severity of asthma on the risk of death.

RESULTS

We confirmed 123 deaths (mortality rate, 6.7 per 100 person-years). In an analysis adjusted for sociodemographics and tobacco history, higher severity-of-asthma scores (hazard ratio [HR], 1.11 per 0.5-SD increase in severity-of-asthma score; 95% confidence interval [CI], 1.01-1.23) and lower perceived asthma control scores (HR, 0.91 per 0.5-SD increase in perceived asthma control score; 95% CI, 0.83-0.99) were each associated with risk of all-cause mortality. In the same adjusted analysis, African American race was not associated with increased mortality risk relative to white race (HR, 0.64; 95% CI, 0.36-1.14).

CONCLUSIONS

In a large managed care organization in which access to care is unlikely to vary widely, greater severity-of-asthma scores and poorer perceived asthma control scores are each associated with increased mortality risk in adults with severe asthma, but African American patients are not at increased risk for death relative to white patients.

BACKGROUND

The contribution of occupational exposures to chronic obstructive pulmonary disease (COPD) and, in particular, their potential interaction with cigarette smoking remains underappreciated.

METHODS

Data from the FLOW study of 1202 subjects with COPD (of which 742 had disease classified as stage II or above by Global Obstructive Lung Disease (GOLD) criteria) and 302 referent subjects matched by age, sex and race recruited from a large managed care organisation were analysed. Occupational exposures were assessed using two methods: self-reported exposure to vapours, gas, dust or fumes on the longest held job (VGDF) and a job exposure matrix (JEM) for probability of exposure based on occupation. Multivariate analysis was used to control for age, sex, race and smoking history. The odds ratio (OR) and adjusted population attributable fraction (PAF) associated with occupational exposure were calculated.

RESULTS

VGDF exposure was associated with an increased risk of COPD (OR 2.11; 95% CI 1.59 to 2.82) and a PAF of 31% (95% CI 22% to 39%). The risk associated with high probability of workplace exposure by JEM was similar (OR 2.27; 95% CI 1.46 to 3.52), although the PAF was lower (13%; 95% CI 8% to 18%). These estimates were not substantively different when the analysis was limited to COPD GOLD stage II or above. Joint exposure to both smoking and occupational factors markedly increased the risk of COPD (OR 14.1; 95% CI 9.33 to 21.2).

CONCLUSIONS

Workplace exposures are strongly associated with an increased risk of COPD. On a population level, prevention of both smoking and occupational exposure, and especially both together, is needed to prevent the global burden of disease.

OBJECTIVE

Because self-rated health (SRH) is strongly associated with health outcomes, it is important to identify factors that individuals take into account when they assess their health. We examined the role of valued life activities (VLAs), the wide range of activities deemed to be important to individuals, in SRH assessments.

STUDY DESIGN AND SETTING

Data were from three cohort studies of individuals with different chronic conditions--rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and chronic obstructive pulmonary disease (COPD). Each cohort's data were collected through structured telephone interviews. Logistic regression analyses identified factors associated with ratings of fair/poor SRH. All analyses included sociodemographic characteristics, general and disease-specific health-related factors, and general measures of physical functioning.

RESULTS

Substantial portions of each group rated their health as fair/poor (RA 37%, SLE 47%, COPD 40%). In each group, VLA disability was strongly associated with fair/poor health (RA: OR=4.44 [1.86,10.62]; SLE: OR=3.60 [2.10,6.16]; COPD: OR=2.76 [1.30,5.85]), even after accounting for covariates.

CONCLUSION

VLA disability appears to play a substantial role in individual perceptions of health, over and above other measures of health status, disease symptoms, and general physical functioning.

BACKGROUND

A previous American College of Chest Physicians Consensus Statement on asthma in the workplace was published in 1995. The current Consensus Statement updates the previous one based on additional research that has been published since then, including findings relevant to preventive measures and work-exacerbated asthma (WEA).

METHODS

A panel of experts, including allergists, pulmonologists, and occupational medicine physicians, was convened to develop this Consensus Document on the diagnosis and management of work-related asthma (WRA), based in part on a systematic review, that was performed by the University of Alberta/Capital Health Evidence-Based Practice and was supplemented by additional published studies to 2007.

RESULTS

The Consensus Document defined WRA to include occupational asthma (ie, asthma induced by sensitizer or irritant work exposures) and WEA (ie, preexisting or concurrent asthma worsened by work factors). The Consensus Document focuses on the diagnosis and management of WRA (including diagnostic tests, and work and compensation issues), as well as preventive measures. WRA should be considered in all individuals with new-onset or worsening asthma, and a careful occupational history should be obtained. Diagnostic tests such as serial peak flow recordings, methacholine challenge tests, immunologic tests, and specific inhalation challenge tests (if available), can increase diagnostic certainty. Since the prognosis is better with early diagnosis and appropriate intervention, effective preventive measures for other workers with exposure should be addressed.

CONCLUSIONS

The substantial prevalence of WRA supports consideration of the diagnosis in all who present with new-onset or worsening asthma, followed by appropriate investigations and intervention including consideration of other exposed workers.

PURPOSE

Although chronic obstructive pulmonary disease (COPD) has a major impact on physical health, the specific impact of COPD on physical functional limitations has not been characterized clearly. We aimed to elucidate the physical functional limitations that are directly attributable to COPD compared to a matched referent group without the condition.

METHODS

We used the Function, Living, Outcomes, and Work (FLOW) cohort study of adults with COPD (n=1202) and referent subjects matched by age, sex, and race (n=302) to study the impact of COPD on the risk of a broad array of functional limitations using validated measures: lower extremity function (Short Physical Performance Battery [SPPB]), submaximal exercise performance (Six Minute Walk Test [SMWT]), standing balance (Functional Reach Test), skeletal muscle strength (manual muscle testing with dynamometry), and self-reported functional limitation (standardized item battery). Multivariate analysis was used to control for confounding by age, sex, race, height, educational attainment, and cigarette smoking.

RESULTS

COPD was associated with poorer lower extremity function (mean SPPB score decrement for COPD vs referent -1.0 points; 95% CI, -1.25 to -0.73 pts) and less distance walked during the SMWT (-334 feet; 95% CI, -384 to -282 ft). COPD also was associated with weaker muscle strength in every muscle group tested, including both the upper and lower extremities (P<.0001 in all cases) and with a greater risk of self-reported functional limitation (OR 6.4; 95% CI, 3.7 to 10.9).

CONCLUSIONS

A broad array of physical functional limitations were specifically attributable to COPD. COPD affects a multitude of body systems remote from the lung.

OBJECTIVES

Self-reported exposure to vapours, gas, dust or fumes (VGDF) has been widely used as an occupational exposure metric in epidemiological studies of chronic lung diseases. Our objective was to characterise the performance of VGDF for repeatability, systematic misclassification, and sensitivity and specificity against exposure likelihood by a job-exposure matrix (JEM).

METHODS

We analysed data from two interviews, 24 months apart, of adults with asthma and chronic rhinitis. Using distinct job as the unit of analysis, we tested a single response item (exposure to VGDF) against assignment using a JEM. We further analysed VGDF and the JEM among a subset of 199 subjects who reported the same job at both interviews, using logistic regression analysis to test factors associated with VGDF inconsistency and discordance with the JEM.

RESULTS

VGDF was reported for 193 (44%) of 436 distinct jobs held by the 348 subjects studied; moderate to high exposure likelihood by JEM was assigned to 120 jobs (28%). The sensitivity and specificity of VGDF against JEM were 71% and 66%, respectively. Among 199 subjects with the same job at both interviews, 32% had a discordant VGDF status (kappa = 0.35). Those with chronic rhinitis without concomitant asthma compared to asthma alone were more likely to have a VGDF report discordant with the JEM (OR 3.6, 95% CI 1.4 to 9.0; p = 0.01). Rhinitis was also associated with reported VGDF in a job classified by the JEM as low exposure (OR 3.9, 95% CI 1.6 to 9.4; p = 0.003).

CONCLUSION

The VGDF item is moderately sensitive measured against JEM as a benchmark. The measure is a useful assessment method for epidemiological studies of occupational exposure risk.

The occupational contribution to chronic obstructive pulmonary disease (COPD) has yet to be put in a global perspective. In the present study, an ecological approach to this question was used, analysing group-level data from 90 sex-specific strata from 45 sites of the Burden of Obstructive Lung Disease study, the Latin American Project for the Investigation of Obstructive Lung Disease and the European Community Respiratory Health Survey follow-up. These data were used to study the association between occupational exposures and COPD Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage II or above. Regression analysis of the sex-specific group-level prevalence rates of COPD at each site against the prevalence of occupational exposure and ever-smoking was performed, taking into account mean smoking pack-yrs and mean age by site, sex, study cohort and sample size. For the entire data set, the prevalence of exposures predicted COPD prevalence (0.8% increase in COPD prevalence per 10% increase in exposure prevalence). By comparison, for every 10% increase in the proportion of the ever-smoking population, the prevalence of COPD GOLD stage II or above increased by 1.3%. Given the observed median population COPD prevalence of 3.4%, the model predicted that a 20% relative reduction in the disease burden (i.e. to a COPD prevalence of 2.7%) could be achieved by a 5.4% reduction in overall smoking rates or an 8.8% reduction in the prevalence of occupational exposures. When the data set was analysed by sex-specific site data, among males, the occupational effect was a 0.8% COPD prevalence increase per 10% change in exposure prevalence; among females, a 1.0% increase in COPD per 10% change in exposure prevalence was observed. Within the limitations of an ecological analysis, these findings support a worldwide association between dusty trades and chronic obstructive pulmonary disease for both females and males, placing this within the context of the dominant role of cigarette smoking in chronic obstructive pulmonary disease causation.

A survey-based COPD severity scoring algorithm could prove useful for targeted disease management and risk-adjustment. For this purpose, we sought to prospectively validate a COPD severity score that had previously been cross-sectionally validated. Using a population-based sample of 267 adults with self-reported physician-diagnosed COPD, we examined the extent to which this COPD severity score predicts future respiratory hospitalizations, emergency department (ED) visits, and outpatient visits. Structured telephone interviews, conducted at baseline and on an annual basis in two subsequent years, determined COPD severity scores and health-care utilization. A basic predictive model for respiratory-specific health-care utilization was developed using sociodemographics, tobacco history, and medical comorbidity data in multivariate logistic regression analysis. The added predictive value of the COPD severity score over and above this basic model was then evaluated by testing the change in model concordance indices. Our analysis demonstrated that the COPD severity score did, in fact, increase the concordance-index of models predicting future respiratory hospitalizations (increase from 80% to 87%; P = 0.03), ED visits (64% to 82%, P = 0.003), and outpatient visits (59% to 77%, P < 0.0001). In a separate analysis, both a greater baseline severity score and worsening of the severity score over time were prospectively associated with each outcome studied (P < 0.05 for each). In conclusion, the COPD severity score adds predictive value in estimating future respiratory-specific health-care utilization and is longitudinally responsive to evolving changes in COPD status over time. This severity score may be used to adjust for disease severity or to identify high-risk populations.

BACKGROUND

Area-level socioeconomic status (SES) may play an important role in drug abuse patterns, including related health outcomes. This may be particularly relevant for gamma-hydroxybutyrate (GHB), which is prototypical of "party" drug abuse.

METHODS

We retrospectively reviewed GHB-related cases reported to the California Poison Control System (CPCS; January 1, 1999 through June 30, 2007). We limited analysis to CPCS calls containing a residential zip code (ZC). The CPCS data were extracted for key case characteristics, including the residential ZC. We linked cases to corresponding 2000 U.S. Census data for area-level measures of SES and demographics. We used multiple logistic regression analysis to test the associations between area-level SES and GHB case severity, taking into account area-level demographics and individual-level GHB high-risk behaviors.

RESULTS

We analyzed 210 cases. Taking into account area-level demographics (age and racial mix; urbanicity) and GHB-related high-risk behaviors (use of GHB congeners; GHB-dependence; co-ingestion of other agents), we associated higher area-level SES with greater GHB case severity. There was 40% increased likelihood of major GHB adverse health outcomes for every $100,000 incremental increase in median home values (OR 1.41; 95% CI 1.1-1.8). For median annual household income (per $10,000), the association was similar (OR 1.39; 95% CI 1.0-1.9).

CONCLUSION

Higher area-level SES is associated with greater GHB-related case severity. This study may serve as a model using a geographic information system (GIS) approach to study the population-based correlates of drugs of abuse reported through poison control surveillance.