Obesity in early adulthood predicts knee pain and walking difficulties among men: A life course study.

BACKGROUND: Few studies have addressed the role of obesity in young adulthood in knee problems later in life. We assessed the associations of overweight/obesity with knee pain and functional limitations of the knee across the life course. METHODS: Military health records from 1967 to 2000 (baseline) were searched for 18- to 50-year-old Finnish men (n = 1913) who participated in the Health 2000 Study (follow-up). Visits to health care were followed during service. Height and weight were measured at baseline and follow-up and waist circumference at follow-up. Weight was inquired at follow-up for ages of 20, 30, 40 and 50 years, if applicable. Life course body mass index (BMI) was calculated. One-month knee pain and functional limitations (walking difficulties and limping) due to knee problems were enquired with interview at follow-up. Cox regression model, logistic regression and trajectory analysis were applied. RESULTS: Body mass index at the age of 20 increased the risk of unilateral knee pain by 38% and functional limitations by 27% for one standard deviation increment of BMI, respectively. One-unit increment of Z-score of life course BMI increased knee pain by 32%. Development of severe obesity during the follow-up increased the risk of knee pain by 80% and functional limitations by 93%. The effect of obesity on functional limitations was partly mediated by traumatic knee problems during military service. CONCLUSIONS: Reducing overweight already in adolescence and avoiding further weight gain during life course may prevent knee pain and associated disability. WHAT DOES THIS STUDY ADD?: BMI at the age of 20 increases the likelihood of knee pain and functional limitations of the knee later in life. Development of severe obesity in adulthood increases the risk of knee pain by 80% and functional limitations by more than 90%. Both general and abdominal obesity are associated with knee pain, associations being stronger for general obesity.

A randomised controlled trial on whether a participatory ergonomics intervention could prevent musculoskeletal disorders.

OBJECTIVES: To examine the efficacy of a participatory ergonomics intervention in preventing musculoskeletal disorders among kitchen workers. Participatory ergonomics is commonly recommended to reduce musculoskeletal disorders, but evidence for its effectiveness is sparse. METHODS: A cluster randomised controlled trial among the 504 workers of 119 kitchens in Finland was conducted during 2002-2005. Kitchens were randomised to an intervention (n = 59) and control (n = 60) group. The duration of the intervention that guided the workers to identify strenuous work tasks and to seek solutions for decreasing physical and mental workload, was 11 to 14 months. In total, 402 ergonomic changes were implemented. The main outcome measures were the occurrence of and trouble caused by musculoskeletal pain in seven anatomical sites, local fatigue after work, and sick leave due to musculoskeletal disorders. Individual level data were collected by a questionnaire at baseline and every 3 months during the intervention and 1-year follow-up period. All response rates exceeded 92%. RESULTS: No systematic differences in any outcome variable were found between the intervention and control groups during the intervention or during the 1-year follow-up. CONCLUSIONS: The intervention did not reduce perceived physical work load and no evidence was found for the efficacy of the intervention in preventing musculoskeletal disorders among kitchen workers. It may be that a more comprehensive redesign of work organisation and processes is needed, taking more account of workers' physical and mental resources.

How consistently distributed are the socioeconomic differences in severe back morbidity by age and gender? A population based study of hospitalisation among Finnish employees.

AIMS: To study the socioeconomic distribution of severe back morbidity by age and gender, and to examine to what extent the differences in back morbidity between socioeconomic groups are particularly related to manual work in different age groups. METHODS: Hospital admissions in 1996 for back disorders of 25-64 year old men (3123 of a total 743,961) and women (3043 of 773,936) from the Finnish Hospital Discharge Register were linked with demographic and socioeconomic data from the 1995 population census. Poisson regression analysis was used to calculate the rate ratios for back related hospitalisation by occupational class and education. The distribution of cases according to occupational status and education was presented in relation to the whole occupationally active workforce by age and gender. RESULTS: Blue-collar (manual) workers had a higher risk of being hospitalised because of back disorders compared with white-collar employees (non-manual) in all age groups among both genders. Manual work versus non-manual work was associated with a 1.3 to 1.4-fold risk (95% CI 1.0 to 1.8) among women and a 1.3 to 1.6-fold risk (95% CI 1.1 to 2.2) among men. The risk of hospitalisation was further inversely associated with educational level within manual and non-manual work in all other age groups except in those aged 55-64 years. Gender related differences were much smaller compared with the socioeconomic ones. CONCLUSIONS: Socioeconomic differences in back morbidity leading to hospitalisation were consistent by age and gender. The results suggest that not only the physical strenuousness of work, but also other causes of severe back disorders are clustered around a subject's socioeconomic status, indicated by formal education. This may have implications for prevention and the planning of rehabilitation.

Respiratory disease and cardiovascular morbidity.

BACKGROUND: Work related dust exposure is a risk factor for acute and chronic respiratory irritation and inflammation. Exposure to dust and cigarette smoke predisposes to exogenous viral and bacterial infections of the respiratory tract. Respiratory infection can also act as a risk factor in the development of atherosclerotic and coronary artery disease. AIMS: To investigate the association of dust exposure and respiratory diseases with ischaemic heart disease (IHD) and other cardiovascular diseases (CVDs). METHODS: The study comprised 6022 dust exposed (granite, foundry, cotton mill, iron foundry, metal product, and electrical) workers hired in 1940-76 and followed until the end of 1992. National mortality and morbidity registers and questionnaires were used. The statistical methods were person-year analysis and Cox regression. RESULTS: Co-morbidity from cardiovascular and respiratory diseases ranged from 17% to 35%. In at least 60% of the co-morbidity cases a respiratory disease preceded a cardiovascular disease. Chronic bronchitis, pneumonia, and upper respiratory track infections predicted IHD in granite workers (rate ratio (RR) = 1.9; 95% CI 1.38 to 2.72), foundry workers (2.1; 1.48 to 2.93), and iron foundry workers (1.7; 1.16 to 2.35). Dust exposure was not a significant predictor of IHD or other CVD in any group. Dust exposure was related to respiratory morbidity. Thus, some respiratory diseases appeared to act as intermediate variables in the association of dust exposure with IHD. CONCLUSION: Dust exposure had only a small direct effect on IHD and other CVD. IHD morbidity was associated with preceding respiratory morbidity. A chronic infectious respiratory tract disease appeared to play an independent role in the development of IHD.

Studies of cytokine levels in bronchoalveolar fluid lavage from patients with interstitial lung diseases.

Cytokine levels in bronchoalveolar lavage fluid from patients with eosinophilic pneumonia (n = 7), allergic alveolitis (n = 11), (cryptogenic) fibrosing alveolitis (n = 8), sarcoidosis (n = 10) were determined, as well as levels in control samples from healthy non-smoking volunteers (n = 11). Fibronectin levels were increased in all the patient categories, the highest absolute levels of fibronectin (100-fold increase) being found in eosinophilic pneumonia and allergic alveolitis. TGF-beta (transforming growth factor-beta) was significantly elevated in allergic alveolitis only. There was a significant difference between allergic alveolitis on the one hand and both sarcoidosis and fibrosing alveolitis on the other. Tumour necrosis factor-alpha (TNF-alpha) was significantly increased in eosinophilic pneumonia and allergic alveolitis; allergic alveolitis and fibrosing alveolitis differed significantly in this respect. Platelet-derived growth factor-BB (PDGF-BB) levels were significantly elevated in allergic alveolitis and fibrosing alveolitis. It was found that the level of PDGF-BB was significantly decreased in the case of sarcoidosis, with no overlapping with allergic alveolitis or fibrosing alveolitis. Interferon-gamma (IFN-gamma) was decreased in all patient categories. A significant difference in extent of the decrease was found between allergic alveolitis and sarcoidosis. The interstitial lung diseases thus differed in the pattern of cytokines expressed, indicating that these cytokines could well be a part of the pathogenic process, and also that the measurement of cytokine levels could be diagnostically useful.

Inpatient hospital care for lumbar intervertebral disc disorders in Finland in relation to education, occupational class, income, and employment.

The object of the study was to describe socioeconomic and demographic determinants of inpatient hospital care for lumbar intervertebral disc disorders (LIDD) in Finland. Information from the 1996 Finnish Hospital Discharge Register was linked with the 1995 Population Census. Poisson regression analyses were made with the total and the gainfully employed workforce aged 20-64 y as reference. All 48 public and seven private acute care general hospitals treating LIDD patients in Finland. In the workforce, 4643 patients aged 20-64 y (3692 among the gainfully employed) were admitted to the hospital due to LIDD (ICD-10: M51.1-M51.9) in 1996. About one-half were treated surgically. The duration of unemployment in 1995 was inversely associated with hospitalisation for LIDD in 1996, allowing for age, sex, education and personal income (unemployed for 12 months vs 0 months: rate ratio 0.66; 95% CI 0.57-0.77). Among those employed for 12 months in 1995, the level of education was inversely associated with the hospital admission rate. The rate was also higher in manual occupations as compared with the upper white-collar employees. The associations were clearer among the medically than the surgically treated patients. Hospitalisation for back disorder was, however, less common in the lowest income group as compared with the highest (0.65; 0.57-0.77) allowing for education, occupational class, age and sex. Women were less often admitted to the hospital than men, allowing for the socioeconomic factors (0.83; 0.77-0.90). When indicated by education or occupation, low socioeconomic status was associated with a relatively high rate of inpatient hospital care for LIDD. When indicated by personal income, the situation was the reverse. Unemployment and female gender predicted a relatively low rate of hospitalisation.

The effect of an irregular shift system on sleepiness at work in train drivers and railway traffic controllers.

Sleepiness and fatigue are frequent problems in railway transportation with occasional monotony and irregular shift schedules. This study aimed at (1) studying the prevalence of severe sleepiness in shifts and (2) examining which shift and sleep-related factors were associated with the occurrence of severe sleepiness in an irregular shift system. A total of 126 randomly selected male train drivers (Tdrs) and 104 railway traffic controllers (Tcos) were investigated using questionnaires and sleep-wake diaries. A sleep diary was used to collect information on sleepiness at work and sleeping times during the 21 consecutive days of the study. The prevalence of severe sleepiness at work (i.e. Karolinska Sleepiness Scale 7 or higher) was modelled by a logistic regression analysis for repeated measurements (GEE) using different shift schedule related factors and sleep length as explanatory variables. Severe sleepiness was reported in 49% (Tdrs) and 50% (Tcos) of the night shifts and in 20% (Tdrs) and 15% (Tcos) of the morning shifts. The odds ratios showed that the risk for severe sleepiness was 6-14 times higher in the night shift and about twice as high in the morning shift compared with the day shift. Age affected the two occupational samples differently: with Tdrs increased age was associated with an additional 8% reduction of risk for severe sleepiness for each year of age, while the Tcos did not show any age dependency. Shift length increased the risk by 15% for each hour of the shift and main sleep period decreased the risk by 15% for each hour of the main sleep. The risk of severe sleepiness was not consistently related to the time-off period before the shifts. The results indicate that adjustments for shift timing, length and off-duty time, in addition to actions aiming at extending the main sleep period, would probably decrease severe sleepiness in railway transportation.

Childhood cancer and parental occupation in the Swedish Family-Cancer Database.

We used the nationwide Swedish Family-Cancer Database to analyze the risk for common childhood tumors in offspring in relation to parental occupation recorded in the census of 1960. A total of 8158 cancer cases, diagnosed before age 15 between years 1958 and 1996, were included. Standardized incidence ratios were calculated using 52 different parental occupations. Among the maternal occupations, seven were associated with the risk of cancer in offspring. Assistant nurses had an excess of children with leukemia and connective tissue and colon cancers. Children of female cooks had brain cancers at a rate greater than expected. Fifteen different malignancies were associated with children of male workers. Shoe and leathers workers' children had excesses of many tumors. Among the other paternal occupations associated with childhood tumors, miners, quarrymen, and hairdressers were likely to be exposed to harmful dusts and chemicals.

Gender-specific incidence trends in lung cancer by histological type in Sweden, 1958-1996.

We used the Swedish Family-Cancer Database to examine the time trends of lung cancer in Sweden by histological type, with special reference to gender. A total of 45,297 lung cancer cases were analysed. The overall age-adjusted incidence rates of squamous cell carcinoma (SCC) in men peaked in the 1980s and then slightly decreased, while corresponding rates in women increased steadily. The incidence of adenocarcinoma increased in both genders. The male-to-female incidence ratio for SCC was 12.4 in the 1960s and 3.6 in the 1990s. For adenocarcinoma the ratio was close to 1.5 throughout the period. Regression analysis indicated that the birth cohort of the 1940s was at the highest risk for adenocarcinoma in men and for all types of lung cancer in women. Lung cancer in parents was a risk factor for offspring. In conclusion, the data, particularly on women, suggest that modern cigarettes induce lung adenocarcinoma and SCC in a proportion of 1:0.6. This proportion was 1:3.7 among men diagnosed in the 1960s. The incidence ratio of 1.3 for adenocarcinoma between men and women in the 1990s is consistent with the smoking prevalence data a few decades ago, suggesting equal sensitivity of both genders to tobacco-induced lung cancer.

Birth order, family size, and the risk of cancer in young and middle-aged adults.

We used the Swedish Family-Cancer Database to analyse the effects of birth order and family size on the risk of common cancers among offspring born over the period 1958-96. Some 1.38 million offspring up to age 55 years with 50.6 million person-years were included. Poisson regression analysis included age at diagnosis, birth cohort, socio-economic status and region of residence as other explanatory variables. The only significant associations were an increasing risk for breast cancer by birth order and a decreasing risk for melanoma by birth order and, particularly, by family size. When details of the women's own reproductive history were included in analysis, birth orders 5-17 showed a relative risk of 1.41. The effects on breast cancer may be mediated through increasing birth weight by birth order. For melanoma, socio-economic factors may be involved, such as limited affordability of sun tourism in large families. Testis cancer showed no significant effect and prostate cancer was excluded from analysis because of the small number of cases.

Parental cancer as a risk factor for nine common childhood malignancies.

The nationwide Swedish Family-Cancer Database was used to analyse childhood tumours among 8158 offspring by parental cancers. The results showed 2-fold familial increases for nervous system cancers and lymphomas, a 6.4-fold increase for endocrine tumours, a 60-fold increased risk for retinoblastomas but no excess risk for leukaemia and Wilms tumour.

Longitudinal study on work related and individual risk factors affecting radiating neck pain.

OBJECTIVES: To study the effects of work related and individual factors affecting radiating neck pain. METHODS: A longitudinal study was carried out with repeated measurements. A total of 5180 Finnish forest industry workers replied to a questionnaire survey in 1992 (response rate 75%). Response rates to follow up questionnaires in 1993, 1994, and 1995 were 83%, 77%, and 90%, respectively. The outcome variable was the number of days with radiating neck pain during the preceding 12 months with three levels (<8, 8-30, >30 days). The generalised estimating equations method was used to fit a marginal model and a transition model was used in a predictive analysis. RESULTS: Items showing associations with radiating neck pain in both analyses were sex, age, body mass index, smoking, duration of work with a hand above shoulder level, mental stress, and other musculoskeletal pains. In the transition model, radiating neck pain in a previous questionnaire was included in the model. Although it was a strong predictor, the variables already mentioned retained their significance. CONCLUSION: Programmes targeted to reduce physical load at work, mental stress, being overweight, and smoking could potentially prevent radiating neck pain.

Familial risks in invasive and in situ cervical cancer by histological type.

The Swedish Family-Cancer Database was used to analyse familial relationships in mothers and daughters with invasive and in situ cervical cancers by histological type during the years 1958-1996, including a total of 21,727 and 191,081 cases, respectively. Familial standardized incidence ratios (SIRs) were calculated separately for mothers and daughters and for invasive and in situ squamous cell carcinoma (SCC) and adenocarcinoma. Familial risks were about 2.0 in invasive SCC and less in in situ SCC. Limited analyses could be carried out on adenocarcinoma because the number of cases was small. However, familial risks were not much smaller in families where only SCC was diagnosed compared with those where both SCC and adenocarcinoma were present. A comparison of cancers between mothers and daughters showed an association between cervical cancer and SCC of skin, and between cervical cancer and smoking-related cancers. The familial risks were unaffected in Poisson regression analysis on many possible intervening variables. The data suggest that host factors modulate an individual's response to human papillomavirus infections.

Genetic epidemiology of multistage carcinogenesis.

It is commonly believed that cancer is a multistage, polygenic disease. Even though conceptually appealing, the evidence supporting the multistage theory remains limited. Most known tumor suppresser genes are associated with monogenic dominant cancers following a two-hit pathway. We review results from a recent twin study on 90000 individuals that give support to the multistage theory. Statistically significant heritability estimates were shown for cancers of the colorectum (35%), breast (27%), and prostate (42%). These estimates are much higher than those obtained from family studies in which parents and offspring, or sibs are compared. The difference can be accounted for by the involvement of many genes. A polygenic cancer would show small effects in family studies but large effects in twin studies. We present calculations on the decrease in familial risks when the number of genes involved increases or when the penetrance decreases. We test the apparent number of stages involved in the main cancers from the Swedish Family-Cancer Database. The logarithms of the slopes suggest large differences in the apparent numbers of mutations involved in different cancers. The number of mutations required appears to be less in familial breast cancer compared to sporadic breast cancer. Study designs for gene identification should be revised to accommodate polygenic cancers.

Age-incidence relationships and time trends in cervical cancer in Sweden.

Age-incidence relationships are informative of carcinogenic mechanisms. These have been previously assessed for cervical squamous cell carcinoma (SCC) but not for adenocarcinoma. The aim was to assess by means of age-, period- and cohort-specific analyses and Poisson regression modelling whether the two types of cervical cancer show an age-incidence maximum at a relatively young age, as shown in cross-sectional analyses. The Swedish Family-Cancer Database was used to analyse age-incidence relationships in cervical SCC and adenocarcinoma diagnosed in years 1958-1996, including a total of 15,118 and 1866 cases, respectively. Area of residence and socio-economic status were included in analyses because they were risk factors of cervical cancer. The analysis of cervical SCC confirmed an incidence maximum at ages 35-39 years. The data for adenocarcinoma also suggested a similar early age maximum but the curves differed extensively by birth cohort. The incidence of adenocarcinoma increased substantially at young age groups towards the end of follow-up. Endometrial adenocarcinoma and vaginal and vulvar SCC, which share some risk factors with cervical cancer, did not show an early age incidence maximum. The results also showed that there was a decrease in the incidence of cervical SCC around year 1960, almost 10 years before the organized population screening, probably due to introduced opportunistic pap testing. The benefits of the organized screening were observed as a further decline in the incidence rates. The unique age-incidence relationships in cervical cancer call for biological explanations.

Factors predictive of ischemic heart disease mortality in foundry workers exposed to carbon monoxide.

The potential predictors of ischemic heart disease mortality were studied for 931 male foundry workers in Finland who participated in a health examination in 1973. These workers were followed up to 1993 through registers and by using a questionnaire. In 1973, the systolic and diastolic blood pressures of workers exposed to carbon monoxide (CO) were slightly higher than those of unexposed workers. The prevalence of angina pectoris showed a clear dose-response relation to CO exposure. Electrocardiogram (ECG) findings indicating past myocardial infarction or suggesting coronary artery disease as a function of smoking and/or CO exposure were not evident. In the 1987 follow-up, the rate ratio for ischemic heart disease mortality was estimated as 4.4 for CO-exposed smokers compared with unexposed nonsmokers. Ischemic heart disease mortality in 1973-1993 was analyzed by using the Cox proportional hazards model. The statistically significant predictors were age, pathologic ECG findings in 1973, regular CO exposure, and abundant alcohol drinking. Of the ECG findings, changes in Q or QS and ST-J or ST waves and in ventricular extrasystoles were statistically significant. The risk of mortality from ischemic heart disease was increased by working in iron foundries, by hypertension, and by smoking.

Predictors and consequences of unemployment among construction workers: prospective cohort study.

OBJECTIVE: To study predictors and consequences of unemployment. DESIGN: Prospective cohort study. SETTING: 11 construction companies in southern Finland. PARTICIPANTS: 586 male employees, aged 40-59 years at baseline in 1991 and not retired during a 4 year follow up. MAIN OUTCOME MEASURES: Long term unemployment, stress symptoms, disease, alcohol consumption, exercise activity, and body mass index. RESULTS: In a multiple logistic regression model, long term unemployment (>24 months v

Breast cancer and occupational exposures in women in Finland.

BACKGROUND: The etiology of breast cancer is not fully understood. Environmental and occupational exposures may contribute to breast cancer risk. METHODS: We linked 324 job titles from the 1970 census of 892,591 Finnish women with incidence of breast cancer (23,638 cases) during 1971-1995. We converted job titles to 31 chemical and two ergonomic agents through a measurement-based, period-specific, national job-exposure matrix. Poisson regression models were fit to the data, with adjustment for birth cohort, follow-up period, socioeconomic status, mean number of children, mean age at first delivery, and turnover rate. RESULTS: For premenopausal breast cancer, medium/high level of occupational exposure to ionizing radiation was associated with a standardized incidence ratio (SIR) of 1.3 (95% confidence interval (CI) 0.7-2.5; trend P = 0.03). For postmenopausal breast cancer, we found on SIR of 1.2 (1.1-1.3) for low level and 1.4 (1.1-1.8) for medium/high level of ionizing radiation (trend P = 0.001); and an SIR 1.3 (1.1-1.7) for medium/high levels of both asbestos and man-made vitreous fibers. Aromatic hydrocarbon solvents showed a significant trend for a modest excess of postmenopausal breast cancer. CONCLUSIONS: Our study indicates that occupational exposure to ionizing radiation may be associated with an increased risk of female breast cancer. High-quality studies on environmental and occupational etiology of breast cancer are needed for further elucidation of risk factors.

Ovarian cancer and occupational exposures in Finland.

BACKGROUND: No single occupational or environmental agent has been established as causing ovarian cancer, existing studies often being based on ecologic or proportional mortality data in which potential confounders related to reproductive history have not been taken into account. METHODS: This study linked 324 job titles of occupationally active Finnish women (n = 892,591) at 1970 census with incidence of ovarian cancer (Finnish Cancer Registry, 5,072 cases) during 1971-1995 (over 15 million person-years). The job titles were converted into indicators of exposure to 33 agents, using a national job-exposure matrix based on measurements and surveys (FINJEM). Poisson regression analyses were performed with stratification by birth cohort, follow-up period, and socioeconomic status, and adjusted for mean number of children, mean age at first delivery, and turnover rate for each job title. RESULTS: We found indications of elevated risks for aromatic hydrocarbon solvents (standardized incidence ratio 1.3 (95% CI 1.0-1.7), leather dust (1.4; 0.7-2.7), man-made vitreous fibers (1.3; 0.9-1.8), and high levels of asbestos (1.3; 0.9-1.8), and diesel (1.7; 0.7-4.1), and gasoline (1.5; 1.0-2.0) engine exhausts). Previously reported findings for hairdressers and women in the printing industry were supported in our data, but not for women in dry cleaning jobs. CONCLUSIONS: Given the various drawbacks in linkage studies and job-exposure matrices, the excesses found in this study need confirmation in individual-level studies.

Low response in white blood cell DNA adducts among workers in a highly polluted cokery environment.

Coke oven workers are often heavily exposed to polynuclear aromatic hydrocarbons (PAHs); this exposure has been associated with higher cancer rates among these workers. We assessed the exposure of cokery workers in an oil shale processing plant. Personal hygienic monitoring, measurement of urinary 1-hydroxypyrene (1-OHP), and analysis of PAH-DNA adducts in white blood cells (WBCs) were performed. The 32P-postlabeling method was used for adduct measurement. The mean adduct value, 1.6 adducts per 10(8) nucleotides, did not differ significantly from the control value (P = 0.098). Smokers had significantly higher adduct levels than non-smoking workers (P = 0.002). 1-OHP levels measured in post-shift samples correlated with DNA adducts found in white blood cells (WBCs). We conclude that hygienic monitoring and measurement of urinary metabolites are essential background exposure data when the biologically effective dose of chemical carcinogens is assessed.