| 1. |
- Björ, Ove, 1967-, et al.
(författare)
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A comparison between standard methods and structural nested modelling when bias from a healthy worker survivor effect is suspected : an iron-ore mining cohort study
- 2015
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Ingår i: Occupational and Environmental Medicine. - : BMJ. - 1351-0711 .- 1470-7926. ; 72:7, s. 536-542
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Tidskriftsartikel (refereegranskat)abstract
- Objectives Iron-ore miners are exposed to extremely dusty and physically arduous work environments. The demanding activities of mining select healthier workers with longer work histories (ie, the Healthy Worker Survivor Effect (HWSE)), and could have a reversing effect on the exposure-response association. The objective of this study was to evaluate an iron-ore mining cohort to determine whether the effect of respirable dust was confounded by the presence of an HWSE. Methods When an HWSE exists, standard modelling methods, such as Cox regression analysis, produce biased results. We compared results from g-estimation of accelerated failure-time modelling adjusted for HWSE with corresponding unadjusted Cox regression modelling results. Results For all-cause mortality when adjusting for the HWSE, cumulative exposure from respirable dust was associated with a 6% decrease of life expectancy if exposed >= 15 years, compared with never being exposed. Respirable dust continued to be associated with mortality after censoring outcomes known to be associated with dust when adjusting for the HWSE. In contrast, results based on Cox regression analysis did not support that an association was present. Conclusions The adjustment for the HWSE made a difference when estimating the risk of mortality from respirable dust. The results of this study, therefore, support the recommendation that standard methods of analysis should be complemented with structural modelling analysis techniques, such as g-estimation of accelerated failure-time modelling, to adjust for the HWSE.
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| 2. |
- Björ, Ove, 1967-, et al.
(författare)
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Do physical workload or temperature characteristics in an outdoor workingenvironment explain deviating rates of mortality and incidental cancer? A cohort study based on iron-ore mining.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background A cohort study that examined iron ore mining found negative associations between cumulative working time employed underground and several severe outcomes. In this cohort study, and using the same group of miners, we examined whether heavy physical workload or the temperature characteristics represented by an outdoor working environment could explain these lower rates.Method This study was based on a Swedish iron ore mining cohort consisting of 13000 workers employed between 1923 and 1998. Exposure was defined as cumulative employment time in heavy physical workload or outdoor work. Poisson regression models were used to generate smoothed estimates of standardized morbidity ratios and adjusted rate ratios, both models by cumulative exposure time. SMRs for different cohort subgroups were used to compare the occurrence of cerebrovascular disease mortality to the reference population.Results The adjusted rate ratio between employment classified as outdoor work ≥25 years and short term outdoor work was 1.62 (95% CI 1.07–2.42). The subgroup underground work ≥15 years deviated most in occurrence of cerebrovascular disease mortality compared with the reference population: SMR (0.70 (95% CI 0.56–0.85)). No elevated rates were associated with cumulative employment time representing heavy physical workloads.Conclusion Employment in temperature shifting outdoor environments was associated with elevated rates of cerebrovascular disease mortality. In contrast, work in tempered underground employment was associated with a protecting effect. Based on selected groups of mortalities, physically heavy workloads did not protect for mortality later in life.
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| 3. |
- Björ, Ove, 1967-
(författare)
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Strategies for assessing health risks from two occupational cohorts within the domain of northern Sweden
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Studies based on a cohort design requires access to both subject-specific and period-specific information. In order to conduct an occupational cohort study, access to exposure information and the possibility and permission to link information on outcomes from other registers are generally necessary. The analysis phase is also aggravated by its added complexity because of the longitudinal dimension of the cohort’s data.This thesis aims at increasing the knowledge on hazards from work on fatalities and cancer within the domain of cohort studies on miners and metal refiners and to study the complexity of the analysis by discussing and suggesting analytical strategies.Methods: The study population for this thesis consisted of a cohort of 2264 blue-collar aluminium smelter workers (paper I) and a cohort of 13000 blue-collar iron-ore miners (papers II-IV), both followed for over 50 years. The outcomes were collected from the Swedish Cause of Death Register and the Swedish Cancer Register. The primary methods of analysis were either Standardized Morbidity Ratios (SMR) or internal comparisons based on Cox or Poisson regression modeling. In paper IV, a g-estimation based on an accelerated failure-time model was performed to estimate the survival ratio.Results: The results from paper I suggested that working as a blue-collar worker metal refiner was associated with increased rates of incidental lung cancer. Elevated rates among short term workers were observed for several outcomes. Paper I also showed that the choice of reference population when calculating SMR could influence the conclusions of the results. In paper II, several outcomes were elevated among the miners compared to the reference population from northern Sweden. However, no outcome except lung cancer was associated with cumulative employment time. The most recurrent pattern of the results was the negative association between cumulative employment time underground and several outcomes. The results from paper III showed that cumulative employment time working outdoors was associated with increased rates of cerebrovascular disease mortality. However, employment with heavy physical workloads did not explain the previously observed decreasing rates in the selected groups of outcomes. The adjustment for the healthy worker survivor effect by g-estimation in paper IV suggested that exposure from respirable dust was associated with elevated mortality risks that could not be observed with standard analytical methods.Conclusion: Our studies found several rates from the cohorts that were elevated compared to external refererence populations but also that long term employments generally were associated with decreasing rates. Furthermore, incidental lung cancer rates was found elevated for the metal refiners. Among the miners, mortality rates of cerebrovascular diseases depended on if work was performed outdoor (higher rates) or underground (lower rates). Methodologically, this thesis has discussed different analytical strategies for handling confounding in occupational cohort studies. Paper IV showed that the healthy worker survivor effect could be adjusted for by performing g-estimation.
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| 4. |
- Einarsson, Sandra, 1981-, et al.
(författare)
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Mapping impact factors leading to the GLIM diagnosis of malnutrition in patients with head and neck cancer
- 2020
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Ingår i: Clinical Nutrition ESPEN. - : Elsevier BV. - 2405-4577. ; 40, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- Background & aims: In head and neck cancer, the combination of weight loss and elevated C-reactive protein levels means that patients have malnutrition as defined by the Global Leadership Initiative on Malnutrition (GLIM). This study aimed to identify impact factors for malnutrition as defined by the GLIM criteria among patients with head and neck cancer at the start of treatment and up to 12 months posttreatment.Methods: In a prospective, observational study, patient, tumour, treatment, and nutritional data from 229 patients with head and neck cancer were collected at the start of treatment and at three follow-ups (7 weeks after the start of treatment and at 3 and 12 months after the termination of treatment). These clinical variables were statistically analysed in relation to malnutrition at each follow-up using univariate and multivariate analyses. Malnutrition was defined according to the two GLIM criteria of >5% body weight loss during the last 6 months and C-reactive protein >5 mg/L.Results: The following factors were predictive for malnutrition in the multivariate analysis performed 7 weeks after the start of treatment: moderate or severe mucositis, chemoradiotherapy +/- surgery, and the need for nutritional support (total or partial use of tube feeding/parenteral nutrition). Advanced tumour stage (III-IV) was significant for malnutrition at the start of treatment and at the 7 week and 3 month follow-ups, but not at 12 months.Conclusions: Severe mucositis, chemoradiotherapy +/- surgery, and advanced tumour stage were found to be impact factors for the diagnosis of malnutrition using GLIM at different follow-up times from the start of treatment up to 12 months after the end of treatment. Few patients with head and neck cancer are diagnosed with malnutrition according to the GLIM criteria in a long-term perspective after the termination of treatment. Research on the validity of the GLIM criteria is needed to build a comprehensive evidence base of impact factors for malnutrition in head and neck cancer.
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| 5. |
- Forsell, Karl, et al.
(författare)
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Cancer incidence in a cohort of Swedish merchant seafarers between 1985 and 2011
- 2022
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Ingår i: International Archives of Occupational and Environmental Health. - : Springer. - 0340-0131 .- 1432-1246. ; 95:5, s. 1103-1111
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Lung cancer, mesothelioma and several lifestyle-associated cancer forms have been reported more common in merchant seafarers. However, few studies reflect recent occupational settings and women seafarers are usually too scarce for meaningful analyses. We conducted a study on cancer incidence between 1985 and 2011 in a Swedish cohort consisting of male and female seafarers.METHODS: All seafarers in the Swedish Seafarers' Register with at least one sea service between 1985 and 2011 and a cumulated sea service time of ≥ 30 days (N = 75,745; 64% men, 36% women; 1,245,691 person-years) were linked to the Swedish Cancer Register and followed-up until 31 December 2011. Standardized incidence ratios (SIR) were calculated with the general population as reference.RESULTS: There were 4159 cancer cases in total, with 3221 among men and 938 among women. Male seafarers had an increased risk of total cancer (SIR 1.05; 95% CI 1.01-1.09), lung cancer (SIR 1.51; 95% CI 1.35-1.67) and urinary bladder cancer (SIR 1.17; 95% CI 1.02-1.33). Several lifestyle-associated cancer forms were more common in men. Previous work on tankers was associated with leukaemia (SIR 1.41; 95% CI 1.00-1.86). The risk of cancer decreased with a start as a male seafarer after 1985, with a significant trend for total cancer (P < 0.001), lung cancer (P = 0.001) and, for tanker seafarers, leukaemia (P = 0.045). Women seafarers had an increased risk of lung cancer (SIR 1.54; 95% CI 1.23-1.87) but the risk of total cancer was not increased (SIR 0.83; 95% CI 0.78-0.89).CONCLUSIONS: In this cohort of merchant Swedish seafarers 1985-2011, the risk of total cancer was increased in men but not in women compared to the general population. Lung cancer was increased in both genders. The risk of cancer seems to decrease over the last decades, but better exposure assessments to occupational carcinogens and longer observation times are needed.
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| 6. |
- Forsell, Karl, et al.
(författare)
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Hematologic malignancy in tanker crewmembers : a case‐referent study among male Swedish seafarers
- 2020
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Ingår i: American Journal of Industrial Medicine. - : John Wiley & Sons. - 0271-3586 .- 1097-0274. ; 63:8, s. 685-692
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Work on Swedish petroleum tankers before the late 1980s has been associated with an increased risk of hematologic malignancy (HM). Since then, ship modernizations have decreased occupational exposure to gases, including the carcinogen benzene. We explored the risk of HMs in Swedish seafarers who had worked on newer types of tankers.METHODS: A case-referent study in male seafarers from a cohort of all Swedish seafarers was set up by record linkage with the Swedish Cancer Registry using the subjects' personal identification number. For each case (N = 315), five referents were randomly chosen from within the cohort, matched by birth year and three different periods of first sea service (<1985, 1985-1991, and ≥1992). Information on the type of ship and dates of service was retrieved from the Swedish Seafarers' Registry. Odds ratios (OR) were calculated by conditional logistic regression together with 95% confidence intervals (CI).RESULTS: The OR of HM was 1.07 (95% CI, 0.80-1.42) for work on tankers. In seafarers that had started to work on tankers ≥1985, the OR was 0.85 (95% CI, 0.50-1.43). For those who started to work on tankers before 1985, the OR was 1.17 (95% CI, 0.84-1.21) and 1.32 (95% CI, 0.86-2.03) if the cumulative time on tankers exceeded 5 years of service. In this last group, the OR of multiple myeloma was 5.39 (95% CI, 1.11-26.1).CONCLUSION: Although limited by crude exposure contrast and a short follow-up, work on tankers after 1985 was not associated with an increased risk of HM among Swedish seafarers.
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| 7. |
- Jeremiasen, Martin, et al.
(författare)
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Improvements in esophageal and gastric cancer care in Sweden-population-based results 2007-2016 from a national quality register
- 2020
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Ingår i: Diseases of the esophagus. - : Oxford University Press (OUP). - 1120-8694 .- 1442-2050. ; 33:3
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish National Register for Esophageal and Gastric cancer was launched in 2006 and contains data with adequate national coverage and of high internal validity on patients diagnosed with these tumors. The aim of this study was to describe the evolution of esophageal and gastric cancer care as reflected in a population-based clinical registry. The study population was 12,242 patients (6,926 with esophageal and gastroesophageal junction (GEJ) cancers and 5,316 with gastric cancers) diagnosed between 2007 and 2016. Treatment strategies, short- and long-term mortality, gender aspects, and centralization were investigated. Neoadjuvant oncological treatment became increasingly prevalent during the study period. Resection rates for both esophageal/GEJ and gastric cancers decreased from 29.4% to 26.0% (P=0.022) and from 38.8% to 33.3% (P=0.002), respectively. A marked reduction in the number of hospitals performing esophageal and gastric cancer surgery was noted. In gastric cancer patients, an improvement in 30-day mortality from 4.2% to 1.6% (P=0.005) was evident. Overall 5-year survival after esophageal resection was 38.9%, being higher among women compared to men (47.5 vs. 36.6%; P<0.001), whereas no gender difference was seen in gastric cancer. During the recent decade, the analyses based on the Swedish National Register for Esophageal and Gastric cancer database demonstrated significant improvements in several important quality indicators of care for patients with esophagogastric cancers. The Swedish National Register for Esophageal and Gastric cancer offers an instrument not only for the control and endorsement of quality of care but also a unique tool for population-based clinical research.
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| 8. |
- Wallner, Bengt, 1962-, et al.
(författare)
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Identifying clinically relevant sliding hiatal hernias : a population-based endoscopy study
- 2018
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Ingår i: Scandinavian Journal of Gastroenterology. - : Taylor & Francis. - 0036-5521 .- 1502-7708. ; 53:6, s. 657-660
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The clinical relevance of small to moderate sliding hiatal hernias is controversial. The aims of the present study were to (1) investigate which symptoms are associated with sliding hiatal hernias and (2) define the length of a sliding hiatal hernia at which gastrointestinal symptoms occur.Methods: A study population representative of the general Swedish population answered a questionnaire regarding gastrointestinal symptoms and was investigated with an upper endoscopy. The length of any sliding hiatal hernia was measured.Results: Only reflux-related symptoms were associated with length of the hiatal hernia (acid regurgitation OR 1.46, CI 1.19–1.79, heartburn OR 1.27, CI 1.05–1.54), and the association did not become significant until an axial hiatal hernia length of 2 cm.Conclusions: Only reflux symptoms could be attributed to sliding hiatal hernias. Hiatal hernias less than 2 cm should be considered clinically insignificant.
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| 9. |
- Wallner, Bengt, 1962-, et al.
(författare)
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Z-line alterations and gastroesophageal reflux : an endoscopic population-based prospective cohort study
- 2019
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Ingår i: Scandinavian Journal of Gastroenterology. - : TAYLOR & FRANCIS LTD. - 0036-5521 .- 1502-7708. ; 54:9, s. 1065-1069
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Tidskriftsartikel (refereegranskat)abstract
- Background and study aims: Barrett's esophagus is a premalignant condition in the distal esophagus associated with esophageal adenocarcinoma. Since gastroesophageal reflux is known to be of etiological importance in both Barrett's esophagus and esophageal adenocarcinoma, we aimed to study which endoscopic alterations at the Z-line can be attributed to a previous history of reflux symptoms. Patients and methods: From 1988, a population cohort in Sweden has been prospectively studied regarding gastrointestinal symptoms, using a validated questionnaire. In 2012, the population was invited to undergo a gastroscopy and participate in the present study. In order to determine which endoscopic alterations that can be attributed to a previous history of gastroesophageal reflux, three different endoscopic definitions of columnar-lined esophagus (CLE) were used: (1) ZAP I, An irregular Z-line with a suspicion of tongue-like protrusions; (2) ZAP II/III, Distinct, obvious tongues of metaplastic columnar epithelium; (3) CLE >= 1 cm, The Prague C/M-classification with a minimum length of 1 cm. Results: A total of 165 community subjects were included in the study. Of these, 40 had CLE >= 1 cm, 99 had ZAP I, and 26 had ZAP II/III. ZAP II/III was associated with an over threefold risk of previous GER symptoms (OR: 3.60, CI: 1.49-8.70). No association was found between gastroesophageal reflux and ZAP I (OR: 2.06, CI: 0.85-5.00), or CLE >= 1 cm (OR: 1.64, CI: 0.77-3.49). Conclusions: In a general community, the only endoscopic alteration to the Z-line definitely linked to longstanding GER symptoms was the presence of obvious tongues of metaplastic columnar epithelium (ZAP II/III).
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