Elbow and wrist/hand symptoms among 6,943 computer operators: a 1-year follow-up study (the NUDATA study)

BACKGROUND: The aim of this study was to examine relations between computer work aspects and elbow and wrist/hand pain conditions and disorders. METHODS: In a 1-year follow-up study among 6,943 technical assistants and machine technicians self-reported active mouse and keyboard time, ergonomic exposures and associations with elbow and wrist/hand pain were determined. Standardized clinical examinations were performed among symptomatic participants at baseline and at follow-up. RESULTS: For continuous duration of mouse time adjusted linear effects were statistically significant for all investigated pain conditions. For continuous duration of keyboard time the corresponding effects were statistically significant for wrist/hand pain conditions except incident 'severe' wrist/hand pain. There were no threshold effects above 0 hr per week (hr/w) of mouse exposure in association with pain conditions, while keyboard exposure showed a threshold effect with 12-month wrist/hand pain at follow-up. Clinical diagnoses were not associated with exposure. CONCLUSIONS: Detailed examination of self-reported exposures showed that mouse and keyboard time predicted elbow and wrist/hand pain from low exposure levels without a threshold effect, but mouse and keyboard time were not predictors of clinical conditions.     

Zero-inflated models for regression analysis of count data: a study of growth and development

Poisson regression is widely used in medical studies, and can be extended to negative binomial regression to allow for heterogeneity. When there is an excess number of zero counts, a useful approach is to used a mixture model with a proportion P of subjects not at risk, and a proportion of 1--P at-risk subjects who take on outcome values following a Poisson or negative binomial distribution. Covariate effects can be incorporated into both components of the models. In child assessment, fine motor development is often measured by test items that involve a process of imitation and a process of fine motor exercise. One such developmental milestone is 'building a tower of cubes'. This study analyses the impact of foetal growth and postnatal somatic growth on this milestone, operationalized as the number of cubes and measured around the age of 22 months. It is shown that the two aspects of early growth may have different implications for imitation and fine motor dexterity. The usual approach of recording and analysing the milestone as a binary outcome, such as whether the child can build a tower of three cubes, may leave out important information.     

Effect of job rotation on need for recovery, musculoskeletal complaints, and sick leave due to musculoskeletal complaints: a prospective study among refuse collectors

BACKGROUND: Job rotation might be an effective preventive measure to reduce the prevalence of musculoskeletal complaints, although its effect has not been yet established. The aim of the present study is to evaluate the effect of job rotation in refuse collecting on need for recovery, prevalence of musculoskeletal complaints, and sick leave due to musculoskeletal complaints. METHODS: A 1-year prospective study among refuse collectors was performed, using standardized questionnaires. Job rotation was performed between collecting two-wheeled containers and driving a refuse truck. The experimental groups of rotating refuse collectors at t(0) and t(1) (group R-R) and non-rotating refuse collectors at t(0) and rotating refuse collectors at t(1) (group NR-R) were compared with a reference group of non-rotating refuse collectors at t(0) and t(1) (group NR-NR). RESULTS: The adjusted need for recovery of group R-R was marginally significantly lower than need for recovery of the reference group. Groups R-R and NR-R had a more than two times higher risk for complaints of the low back than the reference group. No other significant results were found. CONCLUSIONS: Job rotation seemed to coincide with a reduced need for recovery and was associated with an increased risk of low back complaints. No effects were found on sick leave due to musculoskeletal complaints. The results might be influenced by the healthy worker selection effect in the reference group and its inverse in the rotating groups.     

Reliability of data from next-of-kin: results from a case-control study of occupational and lifestyle risk factors for cancer

BACKGROUND: Use of surrogate responders often needs to be considered in case-control studies with a high case fatality. METHODS: Agreement between 98 colon cancer patients and their closest relative was expressed as a percentage of the exact agreement and by Kappa coefficients and intra-class correlation coefficients. RESULTS: The percentage of "don't know" answers was higher for surrogates than for index cases and the highest percentage was seen for questions on early events like childhood diseases. Agreement was best for responses to dichotomous questions on smoking and for prevalent or chronic diseases like diabetes or psoriasis, and lower (54-64%) when a quantitative response of, e.g., smoking was requested. The next-of-kin reported fewer job periods than the study person, 4.5 and 2.8, respectively, and there was a higher agreement for the latest job held than for the longest held job. We found an overall agreement between 91% and 100% for responses to ever having worked in a specific type of industry or occupation. CONCLUSIONS: Use of next-of-kin data will often be a better alternative than excluding severely ill or deceased cases, if the exposure under study correlates with disease progression.     

Tests for gene-environment interaction from case-control data: a novel study of type I error, power and designs

To evaluate the risk of a disease associated with the joint effects of genetic susceptibility and environmental exposures, epidemiologic researchers often test for non-multiplicative gene-environment effects from case-control studies. In this article, we present a comparative study of four alternative tests for interactions: (i) the standard case-control method; (ii) the case-only method, which requires an assumption of gene-environment independence for the underlying population; (iii) a two-step method that decides between the case-only and case-control estimators depending on a statistical test for the gene-environment independence assumption and (iv) a novel empirical-Bayes (EB) method that combines the case-control and case-only estimators depending on the sample size and strength of the gene-environment association in the data. We evaluate the methods in terms of integrated Type I error and power, averaged with respect to varying scenarios for gene-environment association that are likely to appear in practice. These unique studies suggest that the novel EB procedure overall is a promising approach for detection of gene-environment interactions from case-control studies. In particular, the EB procedure, unlike the case-only or two-step methods, can closely maintain a desired Type I error under realistic scenarios of gene-environment dependence and yet can be substantially more powerful than the traditional case-control analysis when the gene-environment independence assumption is satisfied, exactly or approximately. Our studies also reveal potential utility of some non-traditional case-control designs that samples controls at a smaller rate than the cases. Apart from the simulation studies, we also illustrate the different methods by analyzing interactions of two commonly studied genes, N-acetyl transferase type 2 and glutathione s-transferase M1, with smoking and dietary exposures, in a large case-control study of colorectal cancer.     

Medicare claims data reliably identify treatments for basal cell carcinoma and squamous cell carcinoma: a prospective cohort study

Objective: To investigate the accuracy of Medical Benefit Schedule (MBS) item numbers to identify treatments for basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). Methods: We linked records from QSkin Study participants (n=37,103) to Medicare. We measured the proportion of Medicare claims for primary excision of BCC/SCC that had corresponding claims for histopathology services. In subsets of participants, we estimated the sensitivity and external concordance of MBS item numbers for identifying BCC/SCC diagnoses by comparing against ‘gold‐standard’ histopathology reports. Results: A total of 2,821 (7.6%) participants had 4,830 separate Medicare claims for BCC/SCC excision; almost all (97%) had contemporaneous Medicare claims for histopathology services. Among participants with BCC/SCC confirmed by histology reports, 76% had a corresponding Medicare claim for primary surgical excision of BCC/SCC. External concordance for Medicare claims for primary BCC/SCC excision was 68%, increasing to 97% when diagnoses for intra‐epidermal carcinomas and keratoacanthomas were included. Conclusions: MBS item numbers for primary excision of BCC/SCC are reasonably reliable for determining incident cases of keratinocyte skin cancers, but may underestimate incidence by up to 24%. Implications: Medicare claims data may have utility in monitoring trends in conditions for which there is no mandatory reporting.     

Statistical methodology for constructing gestational age-related charts using cross-sectional and longitudinal data: The INTERGROWTH-21st project as a case study

Most studies aiming to construct reference or standard charts use a cross-sectional design, collecting one measurement per participant. Reference or standard charts can also be constructed using a longitudinal design, collecting multiple measurements per participant. The choice of appropriate statistical methodology is important as inaccurate centiles resulting from inferior methods can lead to incorrect judgements about fetal or newborn size, resulting in suboptimal clinical care. Reference or standard centiles should ideally provide the best fit to the data, change smoothly with age (eg, gestational age), use as simple a statistical model as possible without compromising model fit, and allow the computation of Z-scores from centiles to simplify assessment of individuals and enable comparison with different populations. Significance testing and goodness-of-fit statistics are usually used to discriminate between models. However, these methods tend not to be useful when examining large data sets as very small differences are statistically significant even if the models are indistinguishable on actual centile plots. Choosing the best model from amongst many is therefore not trivial. Model choice should not be based on statistical considerations (or tests) alone as sometimes the best model may not necessarily offer the best fit to the raw data across gestational age. In this paper, we describe the most commonly applied methodologies available for the construction of age-specific reference or standard centiles for cross-sectional and longitudinal data: Fractional polynomial regression, LMS, LMST, LMSP, and multilevel regression methods. For illustration, we used data from the INTERGROWTH-21^st Project, ie, newborn weight (cross-sectional) and fetal head circumference (longitudinal) data as examples.     

Policemen and firefighters have increased risk for type-2 diabetes mellitus probably due to their large body mass index: a follow-up study in Japanese men

BACKGROUND: Policemen/firefighters may have increased risk for mortality from ischemic heart disease and from all causes. We compare incidence of type-2 diabetes mellitus (DM), a well-known predictor for mortality, in policemen/firefighters with that in two other worker-groups. METHODS: A follow-up study of 5,130 healthy Japanese men aged 30-49 years at baseline consisted of three worker-groups; 3,111 clerical workers, 1,122 manual/production and transport/communication workers, and 897 policemen/firefighters. Incident DM was identified by "fasting serum glucose >or=7.00 mmol/L" or/and "under medical treatment for DM." Hazard ratio (HR) and 95% confidence interval (95% CI) for incident DM was estimated by Cox's proportional hazard models using clerical workers as a reference group (HR=1.00). Baseline age, body mass index (BMI, kg/m(2)), drinking, smoking, exercise, and education were computed as confounders. RESULTS: During mean follow-up periods of 8.4 years, 155 clerical workers, 51 manual/production and transport/communication workers, and 74 policemen/firefighters had incident DM (5.9, 5.7, and 9.6 per 1,000 person-years, respectively; P=0.001 by chi(2)-test). Policemen/firefighters had significantly increased risk for incident DM against clerical workers (age-adjusted HR (95% CI): 1.65 (1.25, 2.18)), but the significance disappeared after adjustments for BMI (age- and BMI-adjusted HR (95% CI): 1.16 (0.87, 1.54)). Manual/production and transport/communication workers had no increased risk. CONCLUSIONS: Policemen/firefighters have increased risk for DM probably due to their large BMI. Body weight control may be more efficient for prevention of DM and DM-related health problems in policemen/firefighters than in other workers.     

The LNG-IUS study on adenomyosis: a 3-year follow-up study on the efficacy and side effects of the use of levonorgestrel intrauterine system for the treatment of dysmenorrhea associated with adenomyosis

Background

The objective of this study was to evaluate the efficacy and side effects of the levonorgestrel-releasing intrauterine system (LNG-IUS) in the treatment of moderate or severe dysmenorrhea associated with adenomyosis for a 3-year follow-up period.

Study Design

The LNG-IUS was inserted into 94 women who had moderate or severe dysmenorrhea associated with adenomyosis diagnosed by transvaginal sonography during Cycle Days 5-7. A visual analogue scale (VAS) of dysmenorrhea, uterine volume and serum CA125 levels were used to assess the efficacy of the treatment at baseline and 3, 6, 12, 24 and 36 months after the LNG-IUS insertion. Side effects were recorded at every follow-up visit.

Results

The VAS of dysmenorrhea dropped continuously and significantly from the baseline score of 77.9±14.7 to 11.8±17.9 after 36 months of the LNG-IUS insertion (p<.001). The uterine volume decreased significantly from 113.8±46.9 mL to 94.5±40.1 mL (p=.003) at 6 months and to 87.7±35.8 mL (p<.001) at 12 months and then rose slightly, but the variables at 24 and 36 months still decreased significantly in comparison with the baseline variable (p<.001). The serum CA125 levels reduced significantly starting from 6 months after device insertion (p<.001). The most common side effects were weight gain (28.7%), simple ovarian cyst formation (22.3%) and lower abdominal pain (12.8%). At 36 months, the overall satisfaction rate of the treatment was 72.5%.

Conclusions

The LNG-IUS appears to be an effective method in alleviating dysmenorrhea associated with adenomyosis during 3 years. It may be a valuable long-term alternative for the treatment of adenomyosis.     

Flavocoxid is as effective as naproxen for managing the signs and symptoms of osteoarthritis of the knee in humans: a short-term randomized,double-blind pilot study

Flavocoxid (Limbrel), a proprietary mixture of flavonoid molecules (baicalin and catechin), was tested against a traditional nonsteroidal anti-inflammatory drug, naproxen, for the management of the signs and symptoms of moderate osteoarthritis (OA) in humans. Discomfort and global disease activity were used as the primary end points, and safety assessments were also taken for both treatments as a secondary endpoint. In this double-blind study, 103 subjects were randomly assigned to receive either flavocoxid [500 mg twice daily (BID)] or naproxen (500 mg BID) in a 1-month onset of action trial. Outcome measures included the short Western Ontario and McMaster University Osteoarthritis Index, subject Visual Analogue Scale for discomfort and global response, and investigator Visual Analogue Scale for global response and fecal occult blood. Both flavocoxid and naproxen showed significant reduction in the signs and symptoms of knee OA (P ≤ .001). There were no statistically detectable differences between the flavocoxid and naproxen groups with respect to any of the outcome variables. Similarly, there were no statistically detectable differences between the groups with respect to any adverse event, although there was a trend toward a higher incidence of edema and nonspecific musculoskeletal discomfort in the naproxen group. In this short-term pilot study, flavocoxid was as effective as naproxen in controlling the signs and symptoms of OA of the knee and would present a safe and effective option for those individuals on traditional nonsteroidal anti-inflammatory drugs or cyclooxygenase-2 inhibitors. A low incidence of adverse events was reported for both groups.