Parkinson's disease and occupational exposure to organic solvents in Finland: a nationwide case-control study.

OBJECTIVE: This study aimed to investigate the association between Parkinson's disease (PD) and occupational exposure to organic solvents generally and chlorinated hydrocarbons (CHC) in particular. METHODS: We assembled a Finland-wide case-control study for birth years 1930-1950 by identifying incident PD cases from the register of Reimbursement of Medical Costs and drawing two controls per case using incidence density sampling from the Population Information System, matched on sex, birth year, and residency in Finland in 1980-2014. Occupation and socioeconomic status (SES) were identified from national censuses. We assessed cumulative occupational exposures via FINJEM job-exposure matrix. Smoking was based on occupation-specific prevalence by sex from national surveys. We estimated confounder-adjusted PD incidence rate ratios (IRR) via logistic regression and evaluated their sensitivity to errors in FINJEM through probabilistic bias analysis (PBA). RESULTS: Among ever-employed, we identified 17 187 cases (16.0% potentially exposed to CHC) and 35 738 matched controls. Cases were more likely to not smoke and belong to higher SES. Cumulative exposure (CE) to CHC (per 100 ppm-years, 5-year lag) was associated with adjusted IRR 1.235 (95% confidence interval 0.986-1.547), with stronger associations among women and among persons who had more census records. Sensitivity analyses did not reveal notable associations, but stronger effects were seen in the younger birth cohort (1940-1950). PBA produced notably weaker associations, yielding a median IRR 1.097 (95% simulation interval 0.920-1.291) for CHC. CONCLUSION: Our findings imply that PD is unlikely to be related to typical occupational solvent exposure in Finland, but excess risk cannot be ruled out in some highly exposed occupations.

Chronotype and mortality - a 37-year follow-up study in Finnish adults.

The UK Biobank study on chronotype and mortality suggested small increases of all-cause and cardiovascular mortality in a 6.5-year follow-up. Our aim was to constructively replicate findings from it in a longer follow-up. A questionnaire was administered to the population-based adult Finnish Twin Cohort in 1981 (response rate 84%). The study population included 23 854 participants who replied to the question: "Try to assess to what extent you are a morning person or an evening person," with four response alternatives (anchored from "clearly a morning person" to "clearly an evening person"). Vital status and cause of death data were provided by nationwide registers up to the end of 2018. Hazard ratios for mortality were computed based on 8728 deaths. Adjustments were made for education, alcohol, smoking, BMI, and sleep duration. The covariate adjusted model showed a 9% increase of all-cause mortality for the evening-type group (HR = 1.09, 95% CI 1.01-1.18), with attenuation mainly due to smoking and alcohol. Their importance was highlighted by observing no increased mortality among non-smokers who were at most light drinkers. There was no increase in any cause-specific mortality. Our results suggest that there is little or no independent contribution of chronotype to mortality.

The association between night shift work and breast cancer risk in the Finnish twins cohort.

Breast cancer is highly prevalent yet a more complete understanding of the interplay between genes and probable environmental risk factors, such as night work, remains lagging. Using a discordant twin pair design, we examined the association between night shift work and breast cancer risk, controlling for familial confounding. Shift work pattern was prospectively assessed by mailed questionnaires among 5,781 female twins from the Older Finnish Twin Cohort. Over the study period (1990-2018), 407 incident breast cancer cases were recorded using the Finnish Cancer Registry. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for potential confounders. Within-pair co-twin analyses were employed in 57 pairs to account for potential familial confounding. Compared to women who worked days only, women with shift work that included night shifts had a 1.58-fold higher risk of breast cancer (HR = 1.58; 95%CI, 1.16-2.15, highest among the youngest women i.e. born 1950-1957, HR = 2.08; 95%CI, 1.32-3.28), whereas 2-shift workers not including night shifts, did not (HR = 0.84; 95%CI, 0.59-1.21). Women with longer sleep (average sleep duration > 8 h/night) appeared at greatest risk of breast cancer if they worked night shifts (HR = 2.91; 95%CI, 1.55-5.46; Pintx=0.32). Results did not vary by chronotype (Pintx=0.74). Co-twin analyses, though with limited power, suggested that night work may be associated with breast cancer risk independent of early environmental and genetic factors. These results confirm a previously described association between night shift work and breast cancer risk. Genetic influences only partially explain these associations.

Solvent exposed occupations and risk of Parkinson disease in Finland.

INTRODUCTION: Epidemiologic and toxicology studies suggest that exposure to various solvents, especially chlorinated hydrocarbon solvents, might increase Parkinson disease (PD) risk. METHODS: In a population-based case-control study in Finland, we examined whether occupations with potential for solvent exposures were associated with PD. We identified newly diagnosed cases age 45-84 from a nationwide medication reimbursement register in 1995-2014. From the population register, we randomly selected non-PD controls matched on sex, along with birth and diagnosis years (age). We included 11,757 cases and 23,236 controls with an occupation in the 1990 census, corresponding to age 40-60. We focused on 28 occupations with ≥ 5% probability of solvent exposure according to the Finnish Job Exposure Matrix. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) by logistic regression modeling, adjusting for age, sex, socioeconomic status, and smoking probability. RESULTS: Similar proportions of cases (5.5%) and controls (5.6%) had an occupation with potential exposure to any solvents. However, all occupations with a point estimate above one, and all significantly or marginally significantly associated with PD (electronic/telecommunications worker [OR = 1.63, 95% CI 1.05-2.50], laboratory assistant [OR = 1.40, 95% CI 0.98-1.99], and machine/engine mechanic [OR = 1.23, 95% CI 0.99-1.52]) entailed potential for exposure to chlorinated hydrocarbon solvents, specifically. Secondary analyses indicated exposure to polycyclic aromatic hydrocarbons and some metals might contribute to the association for mechanics. CONCLUSION: PD risk might be slightly increased in occupations with potential exposure to chlorinated hydrocarbon solvents. Confirmation is required in additional studies that adjust for other occupational exposures and smoking.

Sleep disruption, chronotype, shift work, and prostate cancer risk and mortality: a 30-year prospective cohort study of Finnish twins.

PURPOSE: Sleep disruption and shift work have been associated with cancer risk, but epidemiologic evidence for prostate cancer remains limited. We aimed to prospectively investigate the association between midlife sleep- and circadian-related parameters and later prostate cancer risk and mortality in a population-based cohort of Finnish twins. METHODS: Data were drawn from the Older Finnish Twin Cohort and included 11,370 twins followed from 1981 to 2012. Over the study period, 602 incident cases of prostate cancer and 110 deaths from prostate cancer occurred. Cox regression was used to evaluate associations between midlife sleep duration, sleep quality, chronotype, and shift work with prostate cancer risk and prostate cancer-specific mortality. Within-pair co-twin analyses were employed to account for potential familial confounding. RESULTS: Compared to "definite morning" types, "somewhat evening" types had a significantly increased risk of prostate cancer (HR 1.3; 95 % CI 1.1, 1.6). Chronotype significantly modified the relationship between shift work and prostate cancer risk (p-interaction <0.001). We found no significant association between sleep duration, sleep quality, or shift work and prostate cancer risk in the overall analyses and no significant association between any sleep- or circadian-related parameter and risk in co-twin analyses. Neither sleep- nor circadian-related parameters were significantly associated with prostate cancer-specific mortality. CONCLUSION: The association between sleep disruption, chronotype, and shift work with prostate cancer risk and mortality has never before been studied in a prospective study of male twins. Our findings suggest that chronotype may be associated with prostate cancer risk and modify the association between shift work and prostate cancer risk. Future studies of circadian disruption and prostate cancer should account for this individual-level characteristic.

Lifestyle counseling in overweight truck and bus drivers - Effects on dietary patterns and physical activity.

UNLABELLED: We studied dietary patterns, physical activity (PA), and monthly goal setting in a weight reduction intervention in long-distance professional drivers. The study was conducted in Finland in 2009-2012. Male drivers with waist circumference > 100 cm were randomized to a lifestyle counseling (LIFE, N = 55) and a reference (REF, N = 58) group. During 12 months, LIFE participated in 6 face-to-face and 7 telephone counseling sessions on diet and PA. Dietary patterns were assessed using an index combining food diary and counselor interview, and PA with the number of daily steps using a pedometer. Monthly lifestyle goals, perceived facilitators and barriers, and adverse effects of PA in the LIFE participants were monitored using counselors' log books. Forty-seven (85%) LIFE participants completed the 12-month program. After 12 months, the mean dietary index score improved by 12% (p = 0.002, N = 24), and the number of daily steps increased by 1811 steps (median; p = 0.01, N = 22). The most frequent dietary goals dealt with meal frequency, plate model, and intake of vegetables, fruits, and berries. The most common PA mode was walking. Typical facilitators to reach monthly lifestyle goals were support from family and friends and ailment prevention; typical barriers were working schedules and ailments. Adverse effects, most commonly musculoskeletal pain, occurred among 83% of the LIFE participants. Positive changes in lifestyle habits were observed during counseling. Monthly lifestyle counseling combining face-to-face and phone contacts seemed appropriate to long-distance drivers. Barriers for reaching lifestyle changes, and adverse effects of PA were common and need to be addressed when planning counseling. TRIAL REGISTRATION: Clinical Trials NCT00893646.

Heritability and mortality risk of insomnia-related symptoms: a genetic epidemiologic study in a population-based twin cohort.

STUDY OBJECTIVES: Our aim was to estimate heritability in phenotypic insomnia and the association between insomnia and mortality. DESIGN: Representative follow-up study. PARTICIPANTS: 1990 survey of the Finnish Twin Cohort (N = 12502 adults; 1554 monozygotic and 2991 dizygotic twin pairs). MEASUREMENTS: Current insomnia-related symptoms (insomnia in general, difficulty in initiating sleep, sleep latency, nocturnal awakening, early morning awakening, and non-restorative sleep assessed in the morning and during the day) were asked. Latent class analysis was used to classify subjects into different sleep quality classes. Quantitative genetic modelling was used to estimate heritability. Mortality data was obtained from national registers until end of April 2009. RESULTS: The heritability estimates of each symptom were similar in both genders varying from 34% (early morning awakening) to 45% (nocturnal awakening). The most parsimonious latent class analysis produced 3 classes: good sleepers (48%), average sleepers (up to weekly symptoms, 40%), and poor sleepers (symptoms daily or almost daily, 12%). The heritability estimate for the cluster was 46% (95% confidence interval 41% to 50%). In a model adjusted for smoking, BMI, and depressive symptoms, the all-cause mortality of poor sleepers was elevated (excess mortality 55% in men and 51% in women). Further adjustment for sleep length, use of sleep promoting medications, and sleep apnea-related symptoms did not change the results. CONCLUSIONS: Insomnia-related symptoms were common in both genders. The symptoms and their clusters showed moderate heritability estimates. A significant association was found between poor sleep and risk of mortality, especially in those with somatic disease.

Shift work and cardiovascular disease - pathways from circadian stress to morbidity.

In order to establish a causal relation between shift work and cardiovascular disease (CVD), we need to verify the pathways from the former to the latter. This paper aims to review the current knowledge of the mechanisms between shift work and CVD. Shift work can increase the risk of CVD by several interrelated psychosocial, behavioral, and physiological mechanisms. The psychosocial mechanisms relate to difficulties in controlling working hours, decreased work-life balance, and poor recovery following work. The most probable behavioral changes are weight gain and smoking. The plausible physiological and biological mechanisms are related to the activation of the autonomic nervous system, inflammation, changed lipid and glucose metabolism, and related changes in the risk for atherosclerosis, metabolic syndrome, and type II diabetes. The data provide evidence for possible disease mechanisms between shift work and CVD, but compelling evidence on any specific mechanism is missing.

Childhood adversities and quality of sleep in adulthood: A population-based study of 26,000 Finns.

OBJECTIVE: To find out if childhood adversities predict poor sleep quality in working age. METHODS: Survey data from the Health and Social Support (HeSSup) study was used (N=25,605, 59% women). Negative childhood adversities and quality of sleep in adulthood were assessed by the questionnaire in 1998. Multinomial regression models were used. RESULTS: A graded association between childhood adversities and the quality of sleep in adulthood was found. Odds ratio (OR) of poor quality of sleep for those with multiple childhood adversities (3-6) was 3.64 (95% CI 2.94-4.50). The association between childhood adversities and the quality of sleep remained significant after adjustments for work status, use of psychotropic drugs, health behaviours, recent life events and child-parent relationships. Poor quality of sleep was clearly increased among those with both poor child-mother (OR 10.4, 95% CI 6.73-16.07) or poor child-father (OR 5.4, 95% CI 3.89-7.50) relationships and multiple childhood adversities. In the analyses of specific childhood adversities, frequent fear of a family member and serious conflicts in the family showed the strongest associations. CONCLUSIONS: The strong association between childhood adversities and the quality of sleep in adulthood highlights the importance of early life circumstances on adult health. Early stage recognition, prevention and supportive measures against childhood adversities and serious family conflicts should be promoted.

High job control enhances vagal recovery in media work.

BACKGROUND: Job strain has been linked to increased risk of cardiovascular diseases. In modern media work, time pressures, rapidly changing situations, computer work and irregular working hours are common. Heart rate variability (HRV) has been widely used to monitor sympathovagal balance. Autonomic imbalance may play an additive role in the development of cardiovascular diseases. AIMS: To study the effects of work demands and job control on the autonomic nervous system recovery among the media personnel. METHODS: From the cross-sectional postal survey of the employees in Finnish Broadcasting Company (n = 874), three age cohorts (n = 132) were randomly selected for an analysis of HRV in 24 h electrocardiography recordings. RESULTS: In the middle-aged group, those who experienced high job control had significantly better vagal recovery than those with low or moderate control (P < 0.01). Among young and ageing employees, job control did not associate with autonomic recovery. CONCLUSIONS: High job control over work rather than low demands seemed to enhance autonomic recovery in middle-aged media workers. This was independent of poor health habits such as smoking, physical inactivity or alcohol consumption.

Sleep duration and breast cancer: a prospective cohort study.

Breast cancer incidence has increased during recent decades for reasons that are only partly understood. Prevalence of sleeping difficulties and sleepiness has increased, whereas sleeping duration per night has decreased. We hypothesized that there is an inverse association between sleep duration and breast cancer risk, possibly due to greater overall melatonin production in longer sleepers. This population-based study includes information from women born in Finland before 1958. Sleep duration, other sleep variables, and breast cancer risk factors were assessed by self-administered questionnaires given in 1975 and in 1981. Breast cancer incidence data for 1976 to 1996 was obtained from the Finnish Cancer Registry. Hazard ratios (HR) and 95% confidence intervals (CI) were obtained from Cox proportional hazards models adjusting for potential confounders. Altogether, 242 cases of breast cancer occurred over the study period among the 12,222 women with sleep duration data in 1975. For these women, the HRs for breast cancer in the short (< or =6 hours), average (7-8 hours), and long sleep (> or =9 hours) duration groups were 0.85 (CI, 0.54-1.34), 1.0 (referent), and 0.69 (CI, 0.45-1.06), respectively. Analysis restricted to the 7,396 women (146 cases) whose sleep duration in 1975 and 1981 were in the same duration group (stable sleepers) yielded HRs of 1.10 (CI, 0.59-2.05), 1.0, and 0.28 (CI, 0.09-0.88), with a decreasing trend (P = 0.03). This study provides some support for a decreased risk of breast cancer in long sleepers.

Reported bruxism and restless legs syndrome in media personnel with or without irregular shift work.

A standardized questionnaire was mailed to all employees of the Finnish Broadcasting Company with irregular shift work (n = 750) and to an equal number of randomly selected controls in the same company with regular 8-h daytime work. The questionnaire covered demographic items, employment details, general health experience, physical status, psychosocial status, stress, work satisfaction and performance, tobacco use, bruxism, and restless legs symptoms (RLS). The aim was to investigate among a multiprofessional media personnel the associations between reported bruxism and RLS, while simultaneously controlling the effects of gender, age, tobacco use, shift work, and dissatisfaction with current workshift schedule. The overall response rate was 58.3% (53.7% men). The response rate in the irregular shift work group was 82.3% (56.6% men) and in the regular daytime work group 34.3% (46.7% men). In the bivariate analyses, RLS was more prevalent in workers at either end of the studied age range (p < 0.05). Self-reported frequent bruxism was significantly associated with younger age (p < 0.05). Females reported RLS (11.4%) slightly more often than males (7.7%) (NS). In logistic regression, frequent bruxism (p < 0.05) and older age (p < 0.05) were significantly positively associated with RLS. Dissatisfaction with one's current workshift schedule (p < 0.05) and RLS (p < 0.05) were significantly positively associated with frequent bruxism, while age (p < 0.05) was significantly negatively associated. In conclusion, perceived bruxism may be a sign of a stressful situation or dissatisfaction, while RLS as a more stable trait may in itself negatively affect sleep quality and further enhance the problem.