Adjustment For Social Class Research Articles

Is there a geographical variation in eczema prevalence in the U.K.? Evidence from the 1958 British birth cohort study

Some studies have suggested that the prevalence of atopic eczema may vary between geographical regions. This descriptive study investigates the regional and subregional geography of reported and examined eczema prevalence at the age of 7, 11 and 16 years in Britain using data from the 1958 birth cohort study (n = 828). Estimates of the relative risk of reported eczema associated with residence in each region of the country were calculated and the regional distribution of reported and examined eczema prevalence was compared. The reported prevalence of eczema was mapped at the smaller county level. Comparisons were made with the county-level distribution of asthma and hay fever prevalence. The study showed a marked and statistically significant variation in eczema prevalence across the regions in Britain which was present for examined as well as reported eczema. The highest risk was associated with four regions: North Midlands; Eastern; London and the South-East; and Southern. This regional pattern was not altered significantly after adjustment for social class and family size. The geographical distribution of eczema prevalence was largely maintained when analysed at the county level. Few similarities were found between the county-level distribution of eczema prevalence and that for asthma and hay fever. Explanations for this strong regional variation now need to be sought in terms of environmental and life-style associations.

Role of dietary factors in ethnic differences in early risk of cardiovascular disease and type 2 diabetes

The disparity in the prevalence of cardiovascular disease and type 2 diabetes between African Americans and whites has been well established, and ethnic differences in several risk factors for these diseases are evident in childhood. The current study explored whether dietary factors explain ethnic differences in serum lipids and insulin profiles in children, independent of body composition and social class background. The sample included 95 African American and white children (mean age: 10.0 y). Macronutrient and food group intakes were derived from three 24-h recalls. Cardiovascular disease and type 2 diabetes risk were determined on the basis of total cholesterol, triacylglycerol, insulin sensitivity (S(i)), and acute insulin response (AIR). Data were analyzed by using t tests, analysis of covariance, and multiple regression. African American children had lower triacylglycerol (P < 0.01), lower S(i) (P < 0.001), and higher AIR (P < 0.001) than whites. Intake of fruit and vegetables was significantly higher, and dairy intake lower, in African American than in white children after adjustment for social class and total energy intake. Several direct relations were observed between diet and insulin action: carbohydrate and fruit intakes were positively associated with S(i) (P = 0.02), and vegetable intake was negatively associated with AIR (P = 0.01). However, neither macronutrient nor food group intake accounted for the ethnic differences in triacylglycerol and AIR. The African American children in our sample showed a greater disease risk than did the white children, even after body composition, social class background, and dietary patterns were adjusted for.

Stillbirths among offspring of male radiation workers at Sellafield nuclear reprocessing plant

Ionising radiation is a known mutagen, but few studies have examined transgenerational effects of paternal exposure in human beings. The workforce at the Sellafield nuclear reprocessing plant in the county of Cumbria, UK, is the most highly exposed workforce in western Europe and North America. This study, which is part of a larger programme of work investigating the health of the children of the Sellafield workforce, set out to find whether there was evidence of an association between stillbirth risk and paternal exposure to ionising radiation. We collected details from birth registration documents for all singleton 248,097 livebirths and 3715 stillbirths in the county of Cumbria 1950-89. Within this cohort the 130 stillbirths and 9078 livebirths to partners of male radiation workers employed at Sellafield were identified. Logistic regression was used to analyse the relation between stillbirth risk and father's preconceptional radiation exposure, with adjustment for social class, year of birth, father's age, and birth order. A significant positive association was found between the risk of a baby being stillborn and the father's total exposure to external ionising radiation before conception (adjusted odds ratio per 100 mSv 1.24 [95% CI 1.04-1.45], p=0.009). The risk was higher for stillbirths with congenital anomaly and was highest for the nine stillbirths with neural-tube defects. The statistical models predicted that, were the association to be interpreted as causal, between 0 and 31.9 of the 130 stillbirths to the workforce may be attributable to father's radiation exposure. The findings of an increased risk of stillbirth with increasing paternal occupational exposure to external radiation are qualitatively consistent with those from animal models, though the risk estimate is higher. Although we cannot exclude the possibility of an unmeasured risk factor for stillbirth, confounded with paternal preconceptional irradiation, extensive checks confirmed that the statistical models were a good fit to the data and there was not statistical evidence of unmeasured factors.

Decision latitude, job strain, and myocardial infarction: a study of working men in Stockholm. The SHEEP Study Group. Stockholm Heart epidemiology Program.

This study examined the role of decision latitude and job strain in the etiology of a first myocardial infarction. Eligible case patients were all full-time working men 45 to 64 years of age who suffered a first myocardial infarction during the period January 1992 to January 1993 in the greater Stockholm region. Referents were selected from the general population. Participation rates were 82% (case patients) and 75% (referents). Both inferred and self-reported low decision latitude were associated with increased risk of a first myocardial infarction, although this association was weakened after adjustment for social class. A decrease in inferred decision latitude during the 10 years preceding the myocardial infarction was associated with increased risk after all adjustments, including chest pain and social class. The combination of high self-reported demands and low self-reported decision latitude was an independent predictor of risk after all adjustments. Both negative change in inferred decision latitude and self-reported job strain are important risk indicators in men less than 55 years of age and in blue-collar workers.

Family conflict and slow growth

AIMSHaving previously observed that slow growth in childhood is associated with subsequent labour market disadvantage, an attempt was made to determine whether family conflict is associated with slow growth to...

Relation of caffeine intake and blood caffeine concentrations during pregnancy to fetal growth: prospective population based study.

To examine the association of plasma caffeine concentrations during pregnancy with fetal growth and to compare this with relations with reported caffeine intake. Prospective population based study. District general hospital, inner London. Women booking for delivery between 1982 and 1984. Stored plasma was available for 1,500 women who had provided a blood sample on at least one occasion and for 640 women who had provided a sample on all three occasions (at booking, 28 weeks, and 36 weeks). Birth weight adjusted for gestational age, maternal height, parity, and sex of infant. The exposures of interest were reported caffeine consumption and blood caffeine concentration. Cigarette smoking was assessed by blood cotinine concentration. Caffeine intake showed no changes during pregnancy, but blood caffeine concentrations rose by 75%. Although caffeine intake increased steadily with increasing cotinine concentration above 15 ng/ml, blood caffeine concentrations fell. Caffeine consumption was inversely related to adjusted birth weight, the estimated effect being a 1.3% fall in birth weight for a 1,000 mg per week increase in intake (95% confidence interval 0.5% to 2.1%). The apparent caffeine effect was confined to cigarette smokers, among whom the estimated effect was-1.6%/1000 mg a week (-2.9% to -0.2%) after adjustment for cotinine and -1.3% (-2.7% to 0.1%) after further adjustment for social class and alcohol intake. Adjusted birth weight was unrelated to blood caffeine concentrations overall (P = 0.09, but a positive coefficient), after adjustment for cotinine (P = 0.73), or among current smokers (P = 0.45). Smokers consume more caffeine than non-smokers. Blood caffeine concentrations during pregnancy are not related to fetal growth, but caffeine intake is negatively associated with birth weight, with this effect being apparent only in smokers. The effect remains of borderline significance after adjustment for other factors. Prudent advice for pregnant women would be to reduce caffeine intake in conjunction with stopping smoking.

Association between incidence of non-Hodgkin's lymphoma and solar ultraviolet radiation in England and Wales.

To examine whether the incidence of non-Hodgkin's lymphoma in different areas of England and Wales is associated with levels of solar ultraviolet radiation. Geographically based study examining the association between incidence of non-Hodgkin's lymphoma and estimated levels of solar ultraviolet radiation, controlling for social class and employment in agriculture. 59 counties in England and Wales. All registered cases of non-Hodgkin's lymphoma during the period 1968-85. Age and sex adjusted odds ratio for non-Hodgkin's lymphoma in each county. Incidence of non-Hodgkin's lymphoma was significantly associated with solar ultraviolet radiation levels (P < 0.001), even after social class and employment in agriculture were controlled for (P = 0.004). In a comparison of counties in the highest and lowest quarters of solar ultraviolet radiation, the relative risk of non-Hodgkin's lymphoma was 1.27 (95% confidence interval 1.24 to 1.29), rising to 1.34 (1.32 to 1.37) after adjustment for social class and employment in agriculture. The incidence of non-Hodgkin's lymphoma in different areas of England and Wales is positively associated with levels of solar ultraviolet radiation. These results are consistent with the hypothesis that exposure to solar ultraviolet radiation increases the risk of non-Hodgkin's lymphoma.

Effect of smoking cessation on cervical lesion size

Summary Background Cigarette smoking has been postulated as a cofactor in the aetiology of cervical cancer, but a causal role is difficult to establish because of potential confounding by sexual behaviour. We have investigated the effect of cessation or reduction in cigarette smoking on the course of minor-grade cervical lesions. Methods In this intervention study 82 women volunteers with minor-grade lesions on colposcopy (cervical intraepithelial neoplasia grade 1 or less) attempted to give up smoking for 6 months. Smoking histories were taken at 3-monthly clinic visits and verified by measurement of salivary cotinine concentrations. At each clinic visit, a photograph of the cervix was taken; the image was digitised and computer-aided image analysis was used to assess lesion size, by investigators unaware of smoking status. Findings Of the 82 women, 17 stopped smoking completely for at least 6 months and 11 others reduced their smoking consumption by more than 75%. Of these 28 women, 23 (82%) showed a reduction in lesion size of at least 20% or 4 mm2 compared with 13 (28%) of the 47 non-quitters (odds ratio 12·0 [95% Cl 3·9-32·7]). The remaining seven women had unconfirmed smoking histories. There was a significant correlation between the extent of smoking reduction and the change in lesion size (X 2 for trend=31·55, p<0·0001). Adjustment for social class, method of contraception, and stage of menstrual cycle did not affect the results. Interpretation Our findings support a link between smoking and cervical disease and suggest that smoking cessation could have a beneficial effect on early cervical abnormalities.

Influences on breast feeding initiation and duration.

The study objectives were to establish the prevalence of breast feeding at birth, at four and twelve weeks after birth and describe the factors associated with its initiation and duration. The study population consisted of all babies born in May 1993 (n = 162) to mothers resident in Kildare. The response rate was 145/162 (89 percent). Mothers were visited within fourteen days of the birth. Breast feeding mothers were re-visited when the baby was four to six weeks old and at twelve to fourteen weeks. Interviews were conducted using an interviewer administered questionnaire. Fifty-five mothers (38%) chose to breast feed at birth. Twelve (8%) had stopped by the first, ten (7%) by the second and fourteen (10%) by the third visit. Higher social class and maternal grandmother having breast fed were significantly associated with initiation (p < 0.05 and p < 0.0005 respectively). Smokers and non-working mothers were significantly less likely to breast feed and smokers had a significantly shorter duration of breast feeding but these associations disappeared on social class adjustment.

Population mixing and sudden infant death syndrome in England and Wales.

Infections may be involved in some cases of sudden infant death syndrome (SIDS). Exposure to such infections is likely to differ considerably between areas depending on rates of population mixing. It is therefore possible that the geography of SIDS will reflect that of population migration. For 403 local authority districts in England and Wales the number of SIDS deaths in the first year of life and the number of livebirths during the period 1979-1983 were abstracted from published sources. Districts were classified by levels of in-migration using data from the 1981 Census and observed and expected numbers of SIDS deaths were compared for areas experiencing different rates of in-migration. A significant association (P < 0.001) was found between SIDS deaths and rates of long distance migration into districts. In the group with the highest rate of long distance in-migration the ratio of observed to expected SIDS deaths was 62% greater than in the group with the lowest rate of in-migration. This association was strengthened after adjustment for social class and illegitimacy. A weaker, but statistically significant, association was found for shorter distance in-migration. It is concluded that geographical variations in SIDS deaths in England and Wales are strongly associated with differences in rates of population mixing as measured by migration. The findings support the hypothesis that population mixing, by its influence on exposure to infections, may be a significant factor in the aetiology of SIDS.

Life expectancy in keratoconus.

It is observed that few patients over the age of 60 regularly attend the keratoconus clinic at Moorfields Eye Hospital. The hypothesis that patients with keratoconus have a shorter life expectancy owing to underlying connective tissue related disease was tested. From patient records a sample of 337 keratoconus patients aged at least 40 years by 1991 were identified, of which 279 were living, 13 were deceased, and 45 were untraceable. The mortality rate for keratoconus patients was compared with that of the general population using actuarial English life tables. Results show no significant difference between the general population mortality rate and that of the keratoconus sample even with adjustment for social class. Possible explanations for the non-attendance of older patients are discussed.

Mortality among United Kingdom servicemen who served abroad in the 1950s and 1960s.

The Registrar General's decennial supplements on occupational mortality provide only limited information on mortality in the armed forces in the United Kingdom. Mortality has therefore been studied among a group of 30,619 United Kingdom servicemen who served abroad in tropical or desert areas in the 1950s and 1960s, and who remained in the services for a total of at least five years. Mortality from all causes of death, all neoplasms, and all other known non-violent causes was lower than that expected from rates for all men in England and Wales, whereas mortality from accidents and violence was raised. These differences remained after adjustment for social class, affected both officers and other ranks, and had not disappeared even after the men had been followed up for at least 20 years. When mortality from 20 specific cancers and 10 other disease groups was examined there were significant excesses for cancers of the oesophagus (standardised mortality ratio (SMR) = 146; p = 0.03) and prostate (SMR = 156; p = 0.03), and significant deficits for cancers of the lung (SMR = 73; p less than 0.001), stomach (SMR = 66; p = 0.002), bladder (SMR = 53; p = 0.02), other specified neoplasms (SMR = 48; p = 0.001), coronary heart disease (SMR = 76; p less than 0.001), bronchitis, emphysema, and chronic obstructive lung disease (SMR = 42; p less than 0.001), and for five further groups of diseases unrelated to smoking or alcohol. Examination of mortality in each of the three services separately identified two specific hazards in the Royal Navy; seven deaths from mesothelioma occurred compared with less than 2.06 expected (p less than 0.005), and there was also an excess of neoplasms and of other diseases associated with alcohol (SMRs of 181 and 229; p = 0.002 and less than 0.001). Mortality from smoking related diseases other than those associated with alcohol was low in all three services, particularly among officers.

Medical morbidity of the homeless.

A prospective study was carried out over a three year period to assess the morbidity pattern of the homeless in Manchester. A principal diagnosis was recorded for each patient consultation during the delivery of primary health care to this population. The diagnoses were grouped and analysed in comparison with expected levels in the general population, both with and without adjustment for social class. Although the total numbers of annual consultations were similar to those expected, the morbidity pattern was very different. High consultation rates in some groups (psychiatric and dermatological conditions) were balanced by low consultation rates in other groups (cardiovascular and musculoskeletal conditions). Thus the provision of primary health care to the homeless is shown to be no greater than to the general population, after adjustment for social class.

Is social class standardisation appropriate in occupational studies?

Social class standardisation has been proposed as a method for separating the effects of occupation and "social" or "lifestyle" factors in epidemiological studies, by comparing workers in a particular occupation with other workers in the same social class. The validity of this method rests upon two assumptions: (1) that social factors have the same effect in all occupational groups in the same social class, and (2) that other workers in the same social class as the workers being studied are free of occupational risk factors for the disease of interest. These assumptions will not always be satisfied. In particular, the effect of occupation will be underestimated when the comparison group also has job-related exposures which cause the disease under study. Thus, although adjustment for social class may minimise bias due to social factors, it may introduce bias due to unmeasured occupational factors. This difficulty may be magnified when occupational category is used as the measure of social class. Because of this potential bias, adjustment for social class should be done only after careful consideration of the exposures and disease involved and should be based on an appropriate definition of social class. Both crude and standardised results should be presented when such adjustments are made.

Type A behaviour and ischaemic heart disease in middle aged British men.

The Bortner questionnaire, which measures aspects of type A (coronary prone) behaviour was completed by 5936 men aged 40-59 selected at random from one general practice in each of 19 British towns. The presence of ischaemic heart disease was determined at initial examination and the men were followed up for an average of 6.2 years for morbidity and mortality from myocardial infarction and for sudden cardiac death. Non-manual workers had significantly higher scores (more type A) than manual workers and the score decreased (less type A) with increasing age. After adjustment for social class and age men with higher scores had higher prevalences of ischaemic heart disease less marked for electrocardiographic evidence and more marked for response to a chest pain questionnaire (angina or possible myocardial infarction). A man's recall of a doctor's diagnosis of ischaemic heart disease, however, did not relate to his Bortner score. There was no significant relation between the Bortner score and the attack rate or incidence of major ischaemic heart disease events. In this study type A behaviour, as measured by the Bortner questionnaire, did not predict major ischaemic heart disease events in British middle aged men.

Unemployment, birthweight, and growth in the first year.

In a cross sectional sample of 655 Glasgow babies the mean birthweight, after adjusting for other factors, of those with unemployed fathers was 150 g less (P less than 0.02) than for babies whose fathers were employed. A longitudinal study of 107 babies from 2 contrasting areas in Glasgow one of which was a socially deprived area was carried out concurrently. The deficit in length of 2.6% for infants from the deprived area at age 12 months was completely explained by adjusting for length at 1 month, father's height, and father's employment status (P less than 0.01). The effect of unemployment on the babies' birthweight was not affected by adjustment for social class. Unemployment may be related to poor infant growth in inner city areas and a national study is needed to see if the recent rise in unemployment has affected this association.

ALCOHOL CONSUMPTION, PREGNANCY, AND LOW BIRTHWEIGHT

The relation between alcohol consumption during pregnancy and birthweight was investigated prospectively in 900 white women. With adjustment for social class and cigarette smoking, women drinking more than 100 g alcohol a week had a risk of delivering a baby on or below the 10th centile more than double that of women drinking less than 50 g a week. The effect of alcohol was synergistic with that of smoking. Drinking at about the time of conception seems to be important for this effect; therefore, health education should be directed at reducing alcohol consumption before pregnancy.

Contribution of social class to differences between single and married men in mortality from peptic ulcer.

SummaryMortality from peptic ulcer among middle-aged Canadian males in the period 1959–63 has been analysed by marital status and social class. Adjustment for social class reduced only slightly the mortality disadvantage of single males compared with married males.