BACKGROUND: A number of studies have shown variations in the occurrence of alcoholism between different socioeconomic groups and occupations, but it has not been clear to what extent this is related to the average alcohol consumption in the same socioeconomic groups or occupations. METHODS: The relationship between socioeconomic group and occupation and hospital discharge 1981-1983 due to 'diagnoses related to alcoholism' (AD) (alcohol psychosis, alcoholism, and alcohol intoxication) and liver cirrhosis was studied in a cohort of 375,035 men and 140,139 women in 13 counties in Sweden who had reported the same occupation in the censuses of 1960 and 1970. Data on alcohol consumption in different socioeconomic groups and occupations were collected from a conscription investigation and from the Swedish twin registry with data from 1969/70 and 1973 respectively. RESULTS: Intermediate or higher non-manual employees had lower risk of AD as well as of liver cirrhosis compared to manual workers for both sexes. Among males several, mostly blue-collar, occupations had increased relative risks of AD. A high level of association was found between the relative risks of AD and liver cirrhosis in socioeconomic groups, and the relative risk of AD in occupations, and the average alcohol consumption in the same socioeconomic groups/occupations among males. Such an association was not evident among women. CONCLUSION: The study shows, contrary to previous Swedish evidence, that there is a strong relationship between the incidence of alcoholism in socioeconomic groups and occupations and the average alcohol consumption in these groups among men.
Sickness absence (SA) is becoming a major economic problem in many countries. Our aim was to investigate whether type of employment, including temporary employment or part-time employment, is associated with SA while controlling for familial factors (genetic and shared environment). Differences between men and women and across employment sectors were explored.
This is a prospective twin study based on 21 105 twins born in Sweden 1959-85. The participants completed a survey in 2005 with follow-up of SA (=15 days), using register data, until end of 2013. The data were analyzed with logistic regression, with results presented as odds ratios (OR) with 95% confidence intervals (CI).
Temporary employment involved higher odds of SA (OR=1.21 95% CI=1.04-1.40) compared to full-time employment. Both part-time workers (OR=0.84 95% CI=0.74-0.95) and the self-employed (OR=0.77 95%CI=0.62-0.94) had lower odds of SA. Stratifying by sex showed lower odds for part-timers (OR=0.82 95% CI=0.73-0.94) and self-employed women (OR=0.65 95% CI=0.47-0.90), but higher odds for men in temporary employment (OR=1.33 95% CI=1.03-1.72). Temporary employees in county councils (OR=1.73 95% CI=1.01-2.99) and municipalities (OR=1.41 95% CI=1.02-1.96) had higher odds while part-timers employed in the private sector had lower odds (OR=0.77 95% CI=0.64-0.93). Familial factors did not confound the association between employment type and SA.
Employment type is associated with SA, with temporary employment involving a higher risk compared to permanent full-time employment while both part-time employment and self-employment involved a lower risk. The associations vary between women and men and across sectors.
BACKGROUND: Various inter-dependent factors influence serum biochemical values. In the elderly, the impact of these factors may differ compared with younger age groups and therefore population-based studies among older people are needed. The specific morbidity in old age, including also various types of drug therapy, should be observed. METHODS: Various biochemical tests in 349 females and 186 males over 81 years of age were carried out and the associations of biochemical values with morbidity, drug therapy, anthropometry and gender were estimated. RESULTS: Biochemical serum values deviate in various diseases, characterized by increased frequency in the elderly, i.e. congestive heart failure, osteoporosis, hip fractures, depression and dementia. All of these diseases present a tendency to increased homocysteine, usually combined with low folate. Cases with intact cognitive function throughout the six years after sampling are characterized by low homocysteine, which is the opposite of what is found in dementia. Furthermore, congestive heart failure is associated with impaired creatinine clearance and increased urea and urate, and osteoporosis and hip fractures are characterized by low albumin and cholesterol. Increased values for urate and impaired creatinine clearance are found in coronary diseases. In gout, multiple biochemical changes take place. For cases with a history of diabetes, arterial hypertension, peptic ulcer and malignancy, few changes are found compared with the values of the total sample. Furosemide therapy is associated with the same pattern as congestive heart failure, and laxative treatment is characterized by low folate and high homocysteine values.
Behaviors related to fertility constitute primary candidates for investigating the relevance of evolutionary influences and biological dispositions on contemporary human behaviors. Using female Danish twin cohorts born 1870-1968, we document important transformations in the relative contributions of "nurture" and "nature" to within-cohort variations in early and complete fertility, and we point toward a systematic relation between the socioeconomic context of cohorts and the relevance of genetic and shared environmental factors. This transformation is most striking for early fertility where genetic factors strengthen over time and are consistent with up to 50 percent of the variation in early fertility in most recent cohorts. Understanding this emerging relevance of genetic factors is of central importance because early fertility constitutes an important determinant of complete fertility levels in low-fertility societies, and because teenage motherhood and early childbearing are often associated with negative life-cycle consequences. Moreover, our results emphasize the need for socially and contextually informed analyses of nature and nurture that allow both factors to influence human reproductive behavior over time.
Hellin's law states that if the twinning rate is w, then the triplet rate is w2, the quadruplet rate is w3, and so forth. The opinion of today is that Hellin's law holds only approximately. In this study the inaccuracy of Hellin's law is studied and the discrepancies are explained mathematically. In our earlier studies we built linear models for the twinning rate. Because most of the mothers are younger than 40 years of age and because in this age interval the twinning rate depends linearly on age, linear regression methods have been applied. Hellin's law suggests using the square-root transformation of the triplet rate r. Statistical arguments speak in favor of using the arcsin square root of r transformation. We discuss both transformations. Despite the fact that Hellin's law is only approximate, the arcsin transformation proves valuable. The transformed triplet rate can be modeled in a way similar to the twinning rate. We consider secular data from Finland for 1881-1990 and from Sweden since 1751. Using Hellin's law, we compare the triplet rates and the twinning rates and study the time trends of the observed twinning and triplet rates. The data are standardized. Our theoretical results are applied to multiple maternity data for Finland. Using maternal age as the regressor, we build a linear model for the twinning rate and for the arcsin-transformed triplet rate. This analysis shows a decreasing linear time trend in the triplet series for the period 1881-1950 but not in the twinning series. The triplet rate has an increasing trend after 1960, which seems to be mainly caused by artificial induction of ovulation.
(1) To provide percentile tables and graphs of birth weight by gestational age and by gender, for singleton and twin liveborn neonates. (2) To determine changes in birth weight relative to gestational age over the study period.
Data on 556,775 singletons and 12,125 twins, born alive in Alberta from 1985 through 1998, were obtained from Alberta Registries - Vital Statistics. Mean birth weights for individual and grouped years were compared by independent two-tailed t-tests. Linear trends in birth weight over the 14-year period were obtained using one-way analyses of variance.
Four tables and corresponding graphs showing birth weight for gestational age by gender for 21 through 44 completed weeks gestation provide data for the 1st to 99th percentile. Changes in birth weight for the combined gestational ages included an increase for singletons (male, F 17.6, p
OBJECTIVE: To assess secular trends for birthweight by gestational age in twins in Norway and to develop current national birthweight standards by gestational age for twin and triplet births using population-based data. MATERIAL AND METHODS: The analysis of secular trends for birthweight and gestational age in twins was based on 32,379 twin livebirths (1967-95). Taking into account the observed secular trends in birthweight for 35-40 weeks of gestation, data on twins born during 1987-95 only were included in the calculation of birthweight percentiles for 35-40 weeks, while for lower and upper weeks, data on twins born during 1967-95 were used. The construction of birthweight-for-gestation curves for triplets was based on the data on 690 triplets. RESULTS: Whereas the overall mean birthweight and gestational age decreased in 1987-95 compared with the previous years, the mean birthweights by gestational age for the 35-40 weeks of gestation was significantly higher in 1987-95. Male twins weighed more than female twins throughout the gestation with consistent and significant differences from 27 to 42 weeks of gestation. Smoothed curves for birthweight-by-gestational-age percentiles of male and female twins are plotted. The birthweight-by-gestational-age curves of triplets were almost identical with twin curves before 30 weeks of gestation, starting to diverge from them progressively thereafter. The intrauterine growth of twin births also starts to differ markedly from singletons at approximately 30 weeks of gestation. CONCLUSION: This study shows that plurality-specific birthweight-by-gestation standards should be used for assessment of fetal growth in multiple births rather than singleton standards.
A time-series analysis by Box-Jenkins modeling of the monthly observations of twin births and singleton births was attempted. The study is population based. The single-birth series has been matched to the twin-birth series for maternal birth cohort, parity of the twin birth, and residence of the parents. Three-hundred forty-one twin pairs and 340 singleton births were grouped into chronological series spanning 72 months of observation. Univariate and bivariate time-series analyses were used. Box-Jenkins modeling shows that both series share the same basic demographic and reproductive risk factors, such as ovulation and conception rates, abortions, sexual intercourse, and the less well-known random events that determine the time of delivery. These factors are randomly related to both birth processes but exert a more important influence on twin births. Beyond these crude features, twin- and single-birth series differ by the frequency of their seasonal cycle. Twin births show low-frequency variations because of a rather limited number of factors that impinge markedly on the twinning process. Single births are subjected to higher frequency variations that can be ascribed to a greater number of structuring factors, the action of which is less pervasive. Only the January peak is common to both types of births. Aside from the common features, the bivariate analysis shows that both series of births are independent, neither being related to the other. It is concluded that the subtle structuring of both processes is largely distinct. The large fraction of the unaccounted variation of each birth process (about 70%) suggests that most of the variation is due to as yet unidentified factors. The search for environmental and geocosmic factors at the origin of conception and confinement should be considered in future undertakings.
To test the hypothesis that in utero exposure to high levels of oestrogen increases the risk of male breast cancer, we followed 115 235 male twins for more than 3.5 million person-years at risk. We observed 11 cases of male breast cancer versus 16.16 expected based on national rates (standardized rate ratio 0.68, 95% confidence interval 0.34-1.22) and conclude that any adverse influence of in utero oestrogen exposure is likely to be small.
OBJECTIVES: Information on health-related outcomes and exposures is available in user-friendly computerized format for the "young cohort" of the Danish Twin Register born 1953-82. We incorporated occupation information within the database to facilitate future job-related studies. METHODS: Occupation information for the 29,430 twins responding to a mailed questionnaire in 1995 was coded according to DISCO-88. The subjects were classified in three ways depending on the information available: directly from the 2,196 job titles listed in the DISCO-88 handbook, according to a set of predetermined rules, or by consensus if ambiguous information was provided. Two percent (2%) of the sample was recoded independently by two investigators to demonstrate coding consistency. RESULTS: Occupation could be directly coded using job titles for 61% of the sample; 15% were coded according to a set of rules or by consensus; 24% could not be coded. The recoded sample was 99% in agreement with the original coding. CONCLUSION: Occupation information has been incorporated within the extensive health-related database for the "young cohort" of the Danish Twin Register. This resource is available to researchers for future studies concerning occupation, health, and heredity using (1) the existing data (2) via linkage to other Danish databases, or (3) by contacting selected subjects directly.