Biomedical subjects

Alex Burdorf

Publications and source records attributed to Alex Burdorf.

41 records · Page 3Linked to original sources

PubMed2002

Statistical power and measurement allocation in ergonomic intervention studies assessing upper trapezius EMG amplitude. A case study of assembly work.

The present study aimed at exploring the statistical power of ergonomic intervention studies using electromyography (EMG) from the upper trapezius muscle. Data from a previous study of cyclic assembly work were reanalyzed with respect to exposure variability between subjects, between days, and within days. On basis of this information, the precision and power of different data collection strategies were explored. A sampling strategy comprising four registrations of about two min each (i.e. two work cycles) for one day per subject resulted in coefficients of variation between subjects on the 10-, 50-, and 90-APDF-percentiles of 0.44, 0.31, and 0.29, respectively. The corresponding necessary numbers of subjects in a study aiming at detecting a 20% exposure difference between two independent groups of equal size were 154, 78, and 68, respectively (p< or = 0.05, power 0.80). Multiple measurement days per subject would improve power, but only to a marginal extent beyond 4 days of recording. Increasing the number of recordings per day would have minor effects. Bootstrap resampling of the data set revealed that estimates of variability and power were associated with considerable uncertainty. The present results in combination with an overview of other occupational studies showed that common-size investigations using trapezius EMG percentiles are at great risk of suffering from insufficient statistical power, even if the expected intervention effect is substantial. The paper suggests a procedure of how to retrieve and use exposure variability information as an aid when studies are planned, and how to allocate measurements efficiently.

Data Interpretation, Statistical↗

PubMed2002

A high hypospadias rate in The Netherlands.

BACKGROUND: Reports on increasing hypospadias trends are based on birth defect registries, which are prone to inaccuracy. We assessed the prevalence of hypospadias precisely, by prospective examination of all newborns in Rotterdam over a 2-year period. METHODS: A total of 7292 consecutive male births were examined for the presence of hypospadias, classified by severity. RESULTS: The frequency of hypospadias in newborn boys was 0.73% (53/7292). The rate among live births was 38 per 10 000, which is 6 times the previously reported rate for the Southwestern Netherlands (6.2) (P < 0.0001). This registry excludes glandular hypospadias. Without glandular cases, our rate is 26 per 10 000, which is still 4-fold higher (P < 0.0001). The ratio of minor to major hypospadias was 0.3. In 79% of cases, surgery was indicated. CONCLUSIONS: We found a 4-fold higher than expected hypospadias rate, which may be explained by case ascertainment differences. The proportion of major cases was higher than generally assumed. This study provides evidence for substantial geographical differences. Explanations for temporal and geographical differences need to be explored. To monitor hypospadias rates and trends accurately, complete case ascertainment, including standardized classification of severity, is warranted.

Cross-Sectional Studies↗

PubMedDate not supplied

Mental work demands protect against cognitive impairment: MAAS prospective cohort study.

Little is known about whether persons with mentally demanding jobs are protected against cognitive impairment and whether this association is independent of intellectual abilities and other confounders. Longitudinal data from the Maastricht Aging Study (MAAS) were used to examine this association. After the 1993-1995 baseline examination, there was a first 3-year follow-up examination (1996-1998) among 630 men and women, aged 50 to 80, who exhibited no cognitive impairment at baseline. Persons with mentally demanding jobs had lower risks of developing cognitive impairment during follow-up (36 cases), compared with persons without such jobs (odds ratio = 0.79; 95% confidence interval: 0.65-0.96). About 1.5% of the persons with high mental work demands developed impairment compared to 4% of the persons with few work demands. The protective effect was independent of intellectual abilities and other confounders. Our findings provide evidence that continued and potentially modifiable mental stimulation during adult life may protect men and women against cognitive impairment.

Aged↗

PubMedDate not supplied

Efficient one-day sampling of mechanical job exposure data--a study based on upper trapezius activity in cleaners and office workers.

This ergonomics exposure assessment study compared the efficiency of eight 1-day-only strategies, that is, the relationship between the number of data collected per subject and the precision of the resulting mean exposure estimate. Whole-day electromyographic recordings from the right upper trapezius muscle in 24 cleaners and 23 office workers were processed to give minute-by-minute values of gap time and jerk time-parameters representing the level and frequency dimensions of muscle activation, respectively. On-site observations provided data on time spent in each of eight exhaustive task categories in the job, seven of which were associated with activities during work, and the last comprising breaks. On average, sampling at fixed intervals without regard to tasks doubled efficiency as compared with random sampling, which in turn was several times as efficient as consecutive sampling. Stratified sampling according to the two broad categories, work and breaks, increased efficiency for random and fixed-interval sampling, but the gain was distinct only among cleaners (about 20%). The commonly used strategy in ergonomic studies of sampling consecutively for short periods within tasks was highly inefficient. Further classification of work into the seven subcategories resulted in marginal additional increases in efficiency; on average less than 2%. A decision algorithm is given for determining appropriate sampling strategies in different types of jobs.

Adult↗

PubMedDate not supplied

Asbestos, asbestos-related diseases, and compensation claims in The Netherlands.

In The Netherlands the number of asbestos-related diseases is increasing. An age-cohort model predicts a steep rise in pleural mesothelioma deaths up to 490 cases per year among men, with a total death toll close over 12,000 cases during 2000-2028. In the past decade the number of compensation claims for asbestos-related diseases has more than doubled, with increasingly verdicts in favor of claimants. In addition to the medical information, information about the state of the art of preventive measures in different periods of time plays a decisive role in these claims. The use of asbestos in The Netherlands, the occurrence of asbestos-related diseases, the national asbestos regulations, and the position of the claimants in asbestos lawsuits in The Netherlands are reviewed.

Asbestosis↗