Francesca Zanardi

Carpal tunnel syndrome and manual work: a longitudinal study.

Objective: To assess risks associated with work-related biomechanical overloads in onset/course of carpal tunnel syndrome. Methods: Workgroups with job tasks spanning different biomechanical exposures were evaluated at baseline in terms of American Conference of Governmental Industrial Hygienists hand-activity/peak force action limit and threshold limit values (TLV). Exposures of interest were “unacceptable” (hand-activity above TLV) and “borderline” (between action limit and TLV) overloads. Clinical/individual data were collected at baseline and 12 months. Results: One-year incidence of “classic/possible” carpal tunnel syndrome symptoms as defined by consensus criteria was 7.3% (153 of 2092). “Unacceptable” overload was associated with a 3-fold increased risk of onset with respect to “acceptable” load. At ordered logistic regression analysis of symptom-status variations, increased risks were recorded for “unacceptable” and “borderline” overloads. Conclusions: Effectiveness of encouraging workplace adherence to the American Conference of Governmental Industrial Hygienists recommendations deserves investigation as a possible key to wide-scale prevention.

Grand Rounds: Could Occupational Exposure to n-Hexane and Other Solvents Precipitate Visual Failure in Leber Hereditary Optic Neuropathy?

Context Leber hereditary optic neuropathy (LHON) is a maternally inherited loss of central vision related to pathogenic mutations in the mitochondrial genome, which are a necessary but not sufficient condition to develop the disease. Investigation of precipitating environmental/occupational (and additional genetic) factors could be relevant for prevention. Case presentation After a 6-month period of occupational exposure to n-hexane and other organic solvents, a 27-year-old man (a moderate smoker) developed an optic neuropathy. The patient had a full ophthalmologic and neurologic investigation, including standardized cycloergometer test for serum lactic acid levels and a skeletal muscle biopsy. His exposure history was also detailed, and he underwent genetic testing for LHON mitochondrial DNA mutations. The patient suffered a sequential optic neuropathy with the hallmarks of LHON and tested positive for the homoplasmic 11778G → A/ND4 mutation. Routine laboratory monitoring revealed increased concentrations of urinary 2.5 hexandione (n-hexane metabolite) and hippuric acid (toluene metabolite) in the period immediately preceding the visual loss. Discussion In a subject carrying an LHON mutation, the strict temporal sequence of prolonged appreciable occupational exposure followed by sudden onset of visual loss must raise a suspicion of causality (with a possible further interaction with tobacco smoke). Relevance In this article, we add to the candidate occupational/environmental triggers of LHON and highlight the need for appropriate case–control (and laboratory) studies to validate the causal effect of mixed toxic exposures.

Search strings for the study of putative occupational determinants of disease.

Objective To identify efficient PubMed search strategies to retrieve articles regarding putative occupational determinants of conditions not generally considered to be work related. Methods Based on MeSH definitions and expert knowledge, we selected as candidate search terms the four MeSH terms describing ‘occupational disease’, ‘occupational exposure’, ‘occupational health’ and ‘occupational medicine’ (DEHM) alongside 22 other promising terms. We first explored overlaps between the candidate terms in PubMed. Using random samples of abstracts retrieved by each term, we estimated the proportions of articles containing potentially pertinent information regarding occupational aetiology in order to formulate two search strategies (one more ‘specific’, one more ‘sensitive’). We applied these strategies to retrieve information on the possible occupational aetiology of meningioma, pancreatitis and atrial fibrillation. Results Only 20.3% of abstracts were retrieved by more than one DEHM term. The more ‘specific’ search string was based on the combination of terms that yielded the highest proportion (40%) of potentially pertinent abstracts. The more ‘sensitive’ string was based on the use of broader search fields and additional coverage provided by other search terms under study. Using the specific string, the numbers of abstracts needed to read to find one potentially pertinent article were 1.2 for meningioma, 1.9 for pancreatitis and 1.8 for atrial fibrillation. Using the sensitive strategy, the numbers needed to read were 4.4 for meningioma, 8.9 for pancreatitis and 10.5 for atrial fibrillation. Conclusions The proposed strings could help health care professionals explore putative occupational aetiology for diseases that are not generally thought to be work related.

Risk factors for operated carpal tunnel syndrome: a multicenter population-based case-control study.

BackgroundCarpal tunnel syndrome (CTS) is a socially and economically relevant disease caused by compression or entrapment of the median nerve within the carpal tunnel. This population-based case-control study aims to investigate occupational/non-occupational risk factors for surgically treated CTS.MethodsCases (n = 220) aged 18-65 years were randomly drawn from 13 administrative databases of citizens who were surgically treated with carpal tunnel release during 2001. Controls (n = 356) were randomly sampled from National Health Service registry records and were frequency matched by age-gender-specific CTS hospitalization rates.ResultsAt multivariate analysis, risk factors were blue-collar/housewife status, BMI ≥ 30 kg/m2, sibling history of CTS and coexistence of trigger finger. Being relatively tall (cut-offs based on tertiles: women ≥165 cm; men ≥175 cm) was associated with lower risk. Blue-collar work was a moderate/strong risk factor in both sexes. Raised risks were apparent for combinations of biomechanical risk factors that included frequent repetitivity and sustained force.ConclusionThis study strongly underlines the relevance of biomechanical exposures in both non-industrial and industrial work as risk factors for surgically treated CTS.

Incidence rates of surgically treated idiopathic carpal tunnel syndrome in blue- and white-collar workers and housewives in Tuscany, Italy

Objectives: Rates of surgically treated carpal tunnel syndrome (CTS) among blue- and white-collar workers and housewives in the general population were compared. Methods: Surgically treated cases of idiopathic CTS were investigated among 25–59-year-old residents of Tuscany, Italy, during 1997–2000, based on obligatory discharge records from all Italian public/private hospitals, archived according to residence on Tuscany’s regional database. Population data were extracted from the 2001 census. Results: After excluding repeat admissions, 8801 eligible cases were identified. Age-standardised rates (per 100 000 person-years) of surgical CTS were: “blue-collar women”, 367.8; “white-collar women”, 88.1; “housewives”, 334.5; “blue-collar men”, 73.5; and “white-collar men”, 15.3. Compared with reference categories (same-sex white-collar workers): female blue-collar workers experienced a 4.2-fold higher standardised rate; housewives, a 3.8-fold excess; and male blue-collar workers, a 4.8-fold excess (all p<0.001). Male and female blue-collar workers showed approximately three to sevenfold higher age-specific rates compared to their white-collar counterparts (all p<0.001). Housewives’ rates were similar to those of blue-collar female workers up to 40–44 years of age, after which they were significantly lower (p<0.002). At all ages, housewives’ rates were much higher (p<0.001) than those of white-collar women. Conclusions: Surgically treated CTS was three to seven times more common (depending on age/gender) in blue-collar than in white-collar workers, which is difficult to explain by differences in body weight or other individual factors. Thus, occupational risk factors seem relevant throughout working life. The high rates for full-time housewives suggest that domestic chores should be investigated as a possible risk factor for CTS.

Incidence rates of in-hospital carpal tunnel syndrome in the general population and possible associations with marital status

BackgroundCarpal tunnel syndrome (CTS) is a socially relevant condition associated with biomechanical risk factors. We evaluated age-sex-specific incidence rates of in-hospital cases of CTS in central/northern Italy and explored relations with marital status.MethodsSeven regions were considered (overall population, 14.9 million) over 3–6-year periods between 1997 and 2002 (when out-of-hospital CTS surgery was extremely rare). Incidence rates of in-hospital cases of CTS were estimated based on 1) codified demographic, diagnostic and intervention data in obligatory discharge records from all Italian public/private hospitals, archived (according to residence) on regional databases; 2) demographic general population data for each region. We compared (using the χscore test) age-sex-specific rates between married, unmarried, divorced and widowed subsets of the general population. We calculated standardized incidence ratios (SIRs) for married/unmarried men and women.ResultsAge-standardized incidence rates (per 100,000 person-years) of in-hospital cases of CTS were 166 in women and 44 in men (106 overall). Married subjects of both sexes showed higher age-specific rates with respect to unmarried men/women. SIRs were calculated comparing married vs unmarried rates of both sexes: 1.59 (95% confidence interval [95% CI], 1.57–1.60) in women, and 1.42 (95% CI, 1.40–1.45) in men. As compared with married women/men, widows/widowers both showed 2–3-fold higher incidence peaks during the fourth decade of life (beyond 50 years of age, widowed subjects showed similar trends to unmarried counterparts).ConclusionThis large population-based study illustrates distinct age-related trends in men and women, and also raises the question whether marital status could be associated with CTS in the general population.

Physical exertion (lifting) and retinal detachment among people with myopia.

Background: People with myopia (near sightedness) are at increased risk for retinal detachment. We explored other factors that may be associated with retinal detachment within this high-risk group. Methods: We conducted a case-control study comprising 61 cases with retinal detachment and myopia and 99 hospital controls who also had myopia. Cases were recruited from a general hospital, and controls from ophthalmologic clinics. Participants compiled a questionnaire including details of past and current occupational lifting tasks to explore Valsalva maneuver as a possible risk factor. We devised a cumulative lifting index to distinguish light and heavy lifting. Results: After adjusting for potential confounders, we found strong associations of retinal detachment with eye surgery, eye or head trauma, severe myopia (all known risk factors), and heavy lifting (vs. no lifting, odds ratio = 4.4 [95% confidence interval = 1.5–13]) and high body mass index (≥25.5 kg/m2, 6.8 [1.6–29]). Conclusions: Heavy occupational lifting and being overweight may be important risk factors for retinal detachment among people with myopia. The role of these risk factors in the etiology of retinal detachment deserves to be explored in more general populations.

Occupational Lifting Tasks and Retinal Detachment in Non-Myopics and Myopics: Extended Analysis of a Case-Control Study

Objectives Lifting heavy weights involves the Valsalva manoeuvre, which leads to intraocular pressure spikes. We used data from a case-control study to further investigate the hypothesis that occupational lifting is a risk factor for retinal detachment. Methods The study population included 48 cases (patients operated for retinal detachment) and 84 controls (outpatients attending an eye clinic). The odds ratios (OR) of idiopathic retinal detachment were estimated with a logistic regression model (adjusted for age, sex and body mass index). Three indexes were used to examine exposure to lifting; 1) maximum load lifted, 2) average weekly lifting, 3) lifelong cumulative lifting. Results For all indexes, the most exposed subjects showed an increased risk of retinal detachment compared with the unexposed (index 1: OR 3.57, 95% confidence interval [CI] 1.21-10.48; index 2: OR 3.24, 95% CI 1.32-7.97; index 3: OR 2.23, 95% CI 1.27-8.74) and dose-response relationships were apparent. Conclusion These results reinforce the hypothesis that heavy occupational lifting may be a relevant risk factor for retinal detachment.

Hidden effectiveness? Results of hand-searching Italian language journals for occupational health interventions.

Objective To compare the yield of hand-searching with optimised electronic search strategies in retrieving occupational health (OH) intervention studies published in a language other than English. Methods The authors systematically hand-searched and screened reports of OH intervention studies published in Italian in peer-reviewed scientific journals between 1990 and 2008. The authors evaluated how many of them met the Cochrane Occupational Safety and Health Review Groups (OSHRG) definition of being an OH intervention study and how many potentially relevant studies retrieved by hand-searching would not be found by PubMed alone using the OSHRGs most specific and most sensitive search strings. Results Hand-searching retrieved 25 articles (reporting 27 studies), including nine not indexed in MEDLINE. Most studies (81%, 22/27) had a before–after design and only one was a randomised trial. The OSHRGs most sensitive search string retrieved all 16 articles published in the Italian language journals that were indexed in MEDLINE, while the most specific search strategy retrieved nine articles (56%, 9/16). The most specific search string showed a lower ‘number needed to read’ value than the most sensitive one (60 vs 132). Conclusions These findings suggest that a sensitive electronic search strategy may be able to find most of the OH interventions published in languages other than English that are indexed in MEDLINE. Hand-searching of important national journals not indexed in MEDLINE should be considered when conducting particularly in-depth research.

Mortality from diabetes and ischaemic heart disease in textile workers

Background To explore explanations for elevated mortality from diabetes among male garment manufacturers and repairers in England and Wales during 1979-1990, analysis was extended by 10 years, looking also at other textile workers and at deaths from ischaemic heart disease (IHD). Methods Data on some 3.5 million deaths were used to compute proportional mortality ratios (PMRs) for diabetes and IHD, standardised for age and social class, in 10 textile-associated job groups, with additional analyses by place of birth for 1993–2000. Results Male mortality from diabetes was elevated in nine of the 10 textile jobs, with overall PMRs of 147 (95% CI 131 to 165) during 1979–90 and 170 (95% CI 144 to 199) during 1991–2000. Proportional mortality from IHD was also consistently high. Female mortality from both diseases was close to that for other occupations. In both sexes, mortality from diabetes and IHD was increased among people born in the Indian subcontinent (PMRs 353 and 139 in men; 262 and 130 in women). In men, the proportion of deceased textile workers born in the Indian subcontinent (11.4%) was much higher than for all occupations (1.8%), but not in women (1.1% vs 0.7%). PMRs for male textile workers standardised for place of birth were lower but still significantly elevated (133, 95% CI 110 to 159 for diabetes; 109, 95% CI 105 to 114 for IHD). Conclusions No obvious occupational hazard explains the increased risk specific to men across a wide range of textile occupations. One possible explanation is uncontrolled residual confounding related to place of birth. This could be tested through suitably designed morbidity surveys.