Shift work, inflammation and musculoskeletal pain-The HUNT Study

BACKGROUND

Studies have indicated that shift work, in particular night work, is associated with chronic musculoskeletal pain but the mechanisms are unclear. It has been suggested that sleep disturbance, a common complaint among shift and night workers, may induce low-grade inflammation as well as heightened pain sensitivity.

AIMS

Firstly, this study was aimed to examine the cross-sectional associations between shift work, C-reactive protein (CRP) level and chronic musculoskeletal pain, and secondly, to analyse CRP as a mediator between shift work and chronic musculoskeletal pain.

METHODS

The study included 23 223 vocationally active women and men who participated in the HUNT4 Survey of the Trøndelag Health Study (HUNT). Information was collected by questionnaires, interviews, biological samples and clinical examination.

RESULTS

Regression analyses adjusted for sex, age and education revealed significant associations between shift work and odds of any chronic musculoskeletal pain (odd ratio [OR] 1.11, 95% confidence interval [CI] 1.04-1.19), between shift work and CRP level (OR 1.09, 95% CI 1.03-1.16) and between CRP level 3.00-10 mg/L and any chronic musculoskeletal pain (OR 1.38, 95% CI 1.27-1.51). Shift work and CRP were also associated with number of chronic pain sites. Mediation analysis indicated that shift work was indirectly associated with any chronic musculoskeletal pain through CRP (OR 1.03, 95% CI 1.01-1.06).

CONCLUSIONS

The results support the hypothesis that shift work is associated with chronic musculoskeletal pain, and that systemic inflammation may be a biological mechanism linking shift work to chronic pain.

Effects of psychosocial work factors on number of pain sites: The role of sleep quality as mediator

Background

Objective of the current study was to determine which of thirteen specific psychosocial work factors were related to number of musculoskeletal pain sites (NPS) prospectively over a two-year time span. Furthermore, the study aimed to explore possible mediation of these prospective relationships through sleep problems.

Methods

The study was a two-wave full panel study. Participants included 6277 employees of Norwegian companies, representing a wide range of occupations. Structural equation modelling was employed to analyze direct and indirect effects of thirteen specific psychological- and social work factors on sleep problems and NPS.

Results

Out of the thirteen work factors studied, positive challenges at work, role conflict, decision control, superior support, coworker support, empowering leadership, and social climate were statistically significantly related to subsequent NPS, both directly and indirectly through sleep quality. Sleep quality was related to NPS in all analyses. Most psychosocial work factors exhibited direct effects on either sleep or number of pain sites. Decision demands and control over work pacing were not statistically significantly related to sleep or pain.

Conclusion

In conclusion, the results suggested sleep quality to be involved in the mechanisms by which work affects the number of pain complaints employees experience.

Significance

Findings from this study suggest sleep may play a role in the complex mechanism from work stressors to musculoskeletal pain. Workplace interventions aiming to reduce musculoskeletal pain may wish to target work factors described in this study, as they affect sleep and may thereby increase number of musculoskeletal pain sites.

Population-based stepwise screening for unrecognised Type 2 diabetes is ineffective in general practice despite reliable algorithms

AIMS/HYPOTHESIS

The yield of screening programmes for Type 2 diabetes in the existing healthcare setting might be lower than anticipated from tests of screening algorithms in data from epidemiological surveys. Our aims were to evaluate the reliability of the algorithms and the effectiveness of a proposed stepwise screening programme for Type 2 diabetes in general practice.

METHODS

The screening programme had four steps: (i) mail-distributed self-administered risk-chart; (ii) screening tests: random blood glucose (RBG) and HbA(1)c; (iii) diagnostic procedure 1 for fasting blood glucose (FBG) (if RBG >/=5.5 mmol/l or HbA(1)c >/=6.1%); and (iv) OGTT as diagnostic procedure 2 (if 5.6</=FBG<6.1 mmol/l or HbA(1)c >/=6.1%). Abnormalities of glucose metabolism were classified according to the WHO 1999 criteria, based on capillary whole blood. The subjects were all patients between 40 and 69 years of age ( n=60,926) who were registered in 88 general practices and had not been previously diagnosed with diabetes.

RESULTS

A total of 11,263 individuals had a high-risk risk-score and attended the screening consultation (step 1 test-positive). Of these, 30.1% needed diagnostic tests (step 2 test-positive) and 27.2% of these needed an OGTT (step 3 test-positive). The test-positive proportions were equal to the proportions obtained in data from a population-based survey from Step 2 onwards, and the algorithms were thus reliable. The identification rate was only 19% of all prevalent undiagnosed diabetes according to a recently published prevalence estimate. This was due to a large dropout rate among high-risk individuals prior to entry into the programme.

CONCLUSIONS/INTERPRETATION

Population-based mail-distributed stepwise screening for Type 2 diabetes in general practice is ineffective, despite reliable screening algorithms, primarily because many high-risk individuals fail to participate.

Influence of temperature and storage time after light exposure on the quinine monohydrochloride chemical actinometric system

The ICH guideline on photostability has proposed quinine monohydrochloride chemical actinometric system as a standard method for measuring light exposure during photostability testing. A change in the absorption at 400 nm of quinine monohydrochloride after light exposure corresponds to a defined dose of light. The present work investigated the effect of temperature, light exposure level and the dark reactions following light exposure on the change of absorbance obtained. The change in the absorbance was linear with respect to time, the rate increased threefold in the temperature range of 25-52 degrees C, and the calculated activation energy was 30 kJ/mol as calculated by the Arrhenius equation. For the dark reactions the change in absorbance was non-linear with respect to time. The rate of the dark reactions was smaller than during light exposure and dependent on the light exposure level prior to the dark reactions. The calculated activation energy of the dark reactions was 18 kJ/mol when calculated by the Arrhenius equation on the initial reaction rates. The different activation energy of the light reaction and the dark reactions indicated different degradation patterns of the two reactions. The present study shows that the absorbance change of quinine monohydrochloride chemical actinometric system is dependent on temperature during light exposure and on storage time and storage temperature after light exposure. The method proposed in the ICH guideline should therefore be optimized in terms of definition of temperature and limitations in storage time after light exposure.

Effects of induced parturition and estradiol on feed intake, liver triglyceride concentration, and plasma metabolites of transition dairy cows

The effect of induced parturition and estradiol on feed intake, liver triglyceride, plasma metabolites, and milk yield was evaluated in fifty-six Holstein cows and heifers. Cows were assigned to treatments on d 260 of gestation and were on trial until d 10 postpartum for measurement of dry matter intake (DMI), plasma metabolites, and liver triglyceride and until d 31 postpartum to measure milk yield. Fourteen animals per group (9 cows and 5 heifers) received either a placebo, 1 mg of fenprostalene, 50 mg of estradiol-17 beta benzoate, or both on d 276 of gestation. Cows that received fenprostalene consumed more dry matter (DM) for the last 8 d prepartum than did cows that did not receive fenprostalene (9.6 kg/d vs. 8.5 kg/d, respectively) but consumed less DM for the first 10 d postpartum (10.9 kg/d vs. 13.1 kg/d, respectively). Cows injected with estradiol-17 beta benzoate tended to consume less DM postpartum than did cows not injected with estradiol-17 beta benzoate (11.3 kg/d vs. 12.7 kg/d, respectively). There was no effect of treatment on milk yield; however, a fenprostalene by day interaction resulted from lower milk yield on d 3, 4, 5, 7, and 10 relative to calving in cows that received fenprostalene. Administration of fenprostalene resulted in a delay in the peak plasma nonesterified fatty acid (NEFA) concentration until 2 d after calving. Plasma glucose concentrations were greatest 1 d prior to calving for cows that received fenprostalene, whereas plasma glucose concentrations peaked on the day of calving for cows that did not receive fenprostalene. Liver triglyceride increased over time; however, there was no effect of treatment on liver triglyceride. Calving induction improved DMI for the last 8 d prepartum, but a concomitant decrease in liver triglyceride after calving did not result. Estradiol-17 beta benzoate had no effect on plasma metabolites or liver triglyceride, indicating that the physiological rise in estradiol prior to calving does not have a primary role in lipolysis or hepatic fatty acid metabolism in the dairy cow.

Bone mineral in pre- and postmenopausal women with insulin-dependent and non-insulin-dependent diabetes mellitus

The aim of the study was to compare bone mineral density (BMD) and bone turnover in pre- and postmenopausal women with insulin-dependent diabetes mellitus (IDDM), non-insulin-dependent diabetes mellitus (NIDDM) and normal reference women. In a cross-sectional study 31 and 11 premenopausal and 22 and 21 postmenopausal IDDM and NIDDM patients, respectively, were recruited from an outpatient clinic. BMD in the forearm, spine, femur and total body and biochemical markers of bone turnover were measured and compared with reference values obtained from measurements of normal healthy pre- and postmenopausal women. Postmenopausally, but not premenopausally, IDDM patients had lower BMD values than NIDDM patients. Postmenopausal NIDDM patients had higher BMD value than normal women. The differences in BMD between IDDM and NIDDM patients could be explained statistically by differences in body weight between the NIDMM (obese) and IDDM (lean) women. Markers of bone turnover were significantly higher postmenopausally than premenopausally in both IDDM and NIDDM patients. Osteocalcin was significantly lower in postmenopausal NIDDM compared with postmenopausal IDDM patients and reference values. Otherwise there were no differences in the markers of bone turnover between NIDDM and IDDM patients. In conclusion, postmenopausal IDDM patients have a relatively decreased BMD, whereas NIDDM patients seem to be relatively protected from postmenopausal bone loss.

Changes in biochemical markers and bone mass after withdrawal of ibandronate treatment: prediction of bone mass changes during treatment

The study was a 1 year randomized, double-blind, placebo-controlled study of ibandronate treatment in postmenopausal, osteopenic women. Participants were followed for 1 year after withdrawal of treatment. All women were at least 10 years past menopause and had a baseline bone mineral density (BMD) at the distal forearm at least 1.5 standard deviations below the premenopausal mean peak value. A total of 141 women (78%) completed the first year, and 119 women (66%) the second year of the study. The dose-response data of the first year have been published previously (Ravn et al. Bone 19:527-533;1996). In this study, we analyzed the biochemical markers as predictors of response in bone mass during ibandronate treatment, and report withdrawal data from the last year of the study, when ibandronate was discontinued. The relative change in the biochemical markers was significantly correlated to the response in BMD. At 12 months, the r values ranged from -0.29 to -0.47 (p < 0.01) and were highest for CrossLaps (uCL) and osteocalcin (OC(N-MID)). The quartiles of women with the most reduced concentrations of uCL and OC(N-MID) during treatment showed a 360-430% higher response in BMD compared to quartiles with less reduced concentrations (p < 0.01). During the withdrawal period, uCL and alkaline phosphatase (AP) returned to baseline values 12 months after discontinuation of treatment in all groups, whereas OC(N-MID) and bone-specific AP were still reduced 10%-25% in the groups previously treated with the highest doses of ibandronate (1.0-5.0 mg) (p < 0.01). In the withdrawal period, BMD decreased equally in all groups (analysis of variance; not significant); with a linear rate of 2%/year on average (p < 0.05 to < 0.001) at the spine and femur. In conclusion, uCL and OC(N-MID) can be used to predict the response in bone mass during ibandronate treatment. The bone loss that resumes after withdrawal of ibandronate treatment is of a magnitude similar to that of normal postmenopausal bone loss.

Leptin in overweight postmenopausal women: no relationship with metabolic syndrome X or effect of exercise in addition to diet

OBJECTIVE

To examine the effect of diet with exercise on serum leptin and whether leptin is associated with the metabolic syndrome X in a high risk population such as overweight postmenopausal women.

STUDY DESIGN AND SUBJECTS

121 healthy overweight, postmenopausal women (aged 49-58y, body mass index (BMI) 25-42 kg/m2) were randomized to: A low-energy-diet, 4.2 MJ/d (n = 51), low-energy-diet + standardized physical exercise (n=49) or no intervention (control: n=21) for 12 weeks, followed by 6 months follow-up without intervention.

MEASUREMENTS

S-leptin was measured by Radio Immuno Assay (RIA), body composition and fat distribution by dual energy X-ray absorptiometry (DEXA) and anthropometry. Factors associated with the metabolic syndrome X and sex hormones were measured.

RESULTS

S-leptin was two-fold higher than in normal-weight postmenopausal women and S-leptin was normalized after weight loss induced by the 12-week low-energy-diet, without any additive effect of the exercise. Of the factors associated with the metabolic syndrome X, serum-leptin correlated significantly only with sex-hormone-binding-globulin and plasminogen-activator-inhibitor-1, whereas factors associated with obesity per se correlated significantly with leptin. Changes in S-leptin correlated with changes in fat tissue mass during the follow-up, but not during the intervention. S-leptin at baseline did not correlate with either short term or long term weight loss.

CONCLUSION

There is no effect of exercise added to diet on S-leptin in overweight postmenopausal women. Leptin does not seem to be associated with the metabolic syndrome X, but rather with fatness. S-leptin is probably associated with both dynamic and static effects of adipose tissue. S-leptin did not predict weight loss.

Effect of method of delivery of propylene glycol on plasma metabolites of feed-restricted cattle

Methods of administering propylene glycol to reduce plasma nonesterified fatty acids (NEFA) during feed restriction of cattle were evaluated. Treatments were 1) no propylene glycol supplementation, 2) propylene glycol provided as an oral drench once per day, 3) propylene glycol mixed with concentrate and fed separately from forage, or 4) propylene glycol blended as part of the total mixed ration (TMR). Prior to or during feed restriction at 50% of ad libitum intake, propylene glycol was provided once daily at 2.5 ml/kg of body weight. Prior to feed restriction, administration of propylene glycol as an oral drench or mixed with concentrate was more effective in increasing serum insulin than was feeding propylene glycol as part of the TMR. During feed restriction, administration of propylene glycol as an oral drench or mixed with concentrate resulted in higher serum insulin and lower plasma NEFA concentrations than did feeding propylene glycol as part of the TMR. Propylene glycol decreased the molar percentage of ruminal acetate and the ratio of acetate to propionate. Propylene glycol administered as an oral drench or mixed with concentrate and fed separately from forage appeared to be more effective than feeding propylene glycol as part of the TMR for influencing plasma NEFA in cattle during feed restriction.

Effects of fenprostalene and estradiol-17 beta benzoate on parturition and retained placenta in dairy cows and heifers

It was hypothesized that a high dose of estrogen in conjunction with a long-acting PGF2 alpha analog would synchronize parturition within a narrow time frame and reduce the incidence of retained placenta. On d 276 of gestation, 14 animals (9 cows and 5 heifers) per group received a placebo (group A), 1 mg of fenprostalene (group B), 50 mg of estradiol-17 beta benzoate (group C), or both (group D). Treatment with estradiol-17 beta benzoate increased serum concentrations of estradiol-17 beta from 228 pg/ml at treatment to 642 and 683 pg/ml at 24 h posttreatment for groups C and D, respectively. Concentration of estradiol-17 beta in group A increased gradually to 526 pg/ml at 24 h prepartum. Progesterone concentrations were reduced by fenprostalene but not by estradiol-17 beta benzoate. Estradiol-17 beta benzoate did not reduce incidence of retained placenta in animals treated with fenprostalene (group B vs. group D) but tended to reduce incidence in uninduced animals (group A vs. group C). Thus, short-term elevation of estradiol-17 beta to normal prepartum concentrations did not regress the corpus luteum, induce parturition, or reduce incidence of retained placenta. However, elevation of estradiol-17 beta for longer periods might enhance placental separation. Conversely, fenprostalene induced calving approximately 2 d after treatment. In this study, 90% of animals treated with fenprostalene calved within a 20-h period, but with a high incidence of retained placenta.