Socioeconomic inequalities in health: individual or area level; does it matter?

In the last decades we have accumulated substantial knowledge about the risk factors that lead to cardiovascular disease. Despite this progress, in this issue of BMC Public Health we learn that little improvement has been made towards reducing inequalities in these risk factors in the UK. Characterizing changes over time can help understanding the mechanisms that underpin health inequalities. These pathways are complex and operate at different levels, from the individual to the context where someone lives. In this commentary I highlight some of the issues and uncertainties that may arise when individual and area level measures are used indistinctively.

Are there socioeconomic inequalities in cardiovascular risk factors in childhood, and are they mediated by adiposity? Findings from a prospective cohort study.

BACKGROUND: Socioeconomic gradients in adiposity were not present during childhood for previous generations, but have emerged in contemporary children. It is unknown whether this translates to socioeconomic gradients in associated cardiovascular risk factors in children, with consequent implications for inequalities in coronary heart disease (CHD) and diabetes when these children reach adulthood. METHODS: Using data from 7772 participants aged 10-years from the Avon Longitudinal Study of Parents and Children, we examined the association between maternal education and a large number of cardiovascular risk factors (cholesterol, triglycerides, high-density lipoprotein, apolipoprotein, adiponectin, leptin, C-reactive protein (CRP), interleukin-6 (IL-6) and systolic and diastolic blood pressure), and examined whether inequalities were mediated by adiposity, measured by dual energy X-ray absorptiometry (DXA)-assessed total fat mass. RESULTS: There were socioeconomic differences in a number of the cardiovascular risk factors (apolipoprotein B, systolic and diastolic blood pressure, CRP, leptin and IL-6). Inequalities were greater in girls than boys. Inequalities in CRP and leptin were completely mediated by adiposity. Inequalities in other cardiovascular risk factors were partially mediated by adiposity. CONCLUSION: This study showed important socioeconomic inequalities in adiposity and associated cardiovascular risk factors in a contemporary UK population of 10-year-old children. Differences between contemporary children and previous generations in the socioeconomic patterning of cardiovascular risk factors suggest future adults may have greater inequalities in diabetes and CHD than current adults. These findings highlight the importance of interventions aimed at preventing obesity in childhood, particularly among those of lower socioeconomic position.

Is the association between childhood socioeconomic circumstances and cause-specific mortality established? Update of a systematic review.

OBJECTIVE: To update a systematic review on the association between childhood socioeconomic circumstances and cause-specific mortality. Studies published since 2003 include a far greater number of deaths than was previously available justifying an update of the previous systematic review. METHODS: Individual-level studies examining childhood socioeconomic circumstances and adult overall and cause-specific mortality published between 2003 and April 2007. RESULTS AND CONCLUSIONS: The new studies confirmed that mortality risk for all causes was higher among those who experienced poorer socioeconomic circumstances during childhood. As already suggested in the original systematic review, not all causes of death were equally related to childhood socioeconomic circumstances. A greater proportion of new studies included women and showed that a similar pattern is valid for both genders. In addition, the new studies show that this association persists among younger birth cohorts, despite temporal general improvements in childhood conditions across successive birth cohorts. The difficulties of establishing a particular life-course model were highlighted.

Association between early life history of respiratory disease and morbidity and mortality in adulthood.

BACKGROUND: Early life exposure to respiratory diseases is associated with lung impairment in adulthood. The objective of this study was to investigate morbidity, and respiratory and other cause specific mortality, among people who reported a medical history of bronchitis, pneumonia and asthma early in life. METHODS: We studied an historical cohort of male students who attended Glasgow University between 1948 and 1968 and for whom long term follow-up and cause specific mortality were available (9544 students, 1553 deaths). A medical history of respiratory diseases, including bronchitis, pneumonia and asthma, along with other disease risk factors and socioeconomic conditions, were collected during university health examinations. A subsample responded to a postal follow-up in adulthood (n = 4044), which included respiratory and other chronic disease questions. RESULTS: A medical history of a respiratory disease (bronchitis, pneumonia and asthma) in early life was associated with a 57% greater risk of overall respiratory disease mortality in adulthood and a more than twofold increase in chronic obstructive pulmonary disease mortality (fully adjusted hazard ratio (HR) 2.37; 95% CI 1.16, 4.83). In addition, students reporting a history of bronchitis had a 38% higher risk of cardiovascular disease mortality (95% CI 1.06, 1.80). Respiratory disease in early life was also associated with a higher risk in adulthood of chronic phlegm, dyspnoea and doctor's diagnosis of asthma, bronchitis and emphysema (adjusted odds ratios ranging from 1.40 to 6.95 for these outcomes). CONCLUSION: An early life history of respiratory diseases is associated with higher mortality and morbidity risk in adulthood in men, the associations being seen particularly for respiratory related and cardiovascular deaths among those with a history of bronchitis. All early life respiratory diseases appeared to be negatively associated with later adult respiratory health.

Association between number of siblings and cause-specific mortality in the Glasgow alumni cohort study.

In the Glasgow University Alumni cohort, students with no siblings experienced higher respiratory disease mortality. This risk diminished after accounting for potential confounders. We did not find strong evidence of an association with all cause, coronary heart disease, stroke or stomach cancer mortality. Number of siblings is a proxy for other exposures and exploring its association with specific disease outcomes can help disentangle some of the pathways relating early life exposures to adult mortality.

Association between sibship size and allergic diseases in the Glasgow Alumni Study.

BACKGROUND: Recent epidemiological studies consistently report an inverse association between sibship size and allergic disease, but evidence from individuals born before the 1980s is inconsistent. As information on relative permanence of this finding may offer clues to its biological explanation, the association between sibship size and allergic disease in individuals born between 1918 and 1952 was investigated. METHODS: Cross sectional surveys conducted by the Student Health Service at the University of Glasgow (1948-68) provided data on 14 140 men and women aged 16-30 years at the time of examination. The main outcome measures studied were self-reported asthma, eczema-urticaria, and hay fever. RESULTS: A total of 1677 individuals (11.9%) provided a positive history of at least one of the three allergic diseases: 457 (3.2%) asthma, 594 (4.2%) eczema-urticaria, and 885 (6.3%) hay fever. Compared with those without siblings (reference odds ratio = 1), the odds ratios (95% confidence intervals) for having any allergic disease among those with one, two or three siblings were 0.86 (0.75 to 0.99), 0.80 (0.69 to 0.93), and 0.70 (0.60 to 0.83), respectively (p(trend)<0.001). Increasing birth order and low socioeconomic position in childhood were associated with a lower risk of allergy. Adjustment for birth order, year of birth, age, sex, socioeconomic position in childhood, and family history of allergy did not materially alter the results. CONCLUSIONS: There is a robust inverse association between sibship size and allergic disease even among people born in the first half of the 20th century. These results favour relatively time-independent explanations for this phenomenon (such as the hygiene hypothesis or parity related changes in the intrauterine environment) over new environmental exposures.

Trends in resting pulse rate among students attending Glasgow University between 1948 and 1968: analyses of cross sectional surveys.

Evidence on long-term trends in physical activity is limited. We report that resting pulse rates--a proxy indicator of physical activity and fitness--increased among young adults attending Glasgow University between 1948 and 1968.

Lifecourse weight patterns and adult-onset diabetes: the Glasgow Alumni and British Women's Heart and Health studies.

OBJECTIVE: To examine the association between body weight measures across the lifecourse and the risk of adult-onset diabetes. METHODS: We analysed data from the Glasgow Alumni Cohort and the British Women's Heart and Health Study (BWHHS). The former included 5,571 men and women who had height and weight measured at university, and reported birthweight, mid- and later-life weight in a postal questionnaire. The BWHHS analysis included 4,280 women who had height and weight measured in later adulthood and recalled their birthweight and early adult height and weight. Adult-onset diabetes was defined as doctor-diagnosed disease after age 30, either self-reported or abstracted from medical records. RESULTS: Thirty nine women and 209 men (Glasgow Alumni study) and 314 women (BWHHS) had diabetes. Those with diabetes had lower mean birthweight than those without, although the differences were small. Individuals with diabetes were also shorter and heavier at all ages than those without diabetes. Being overweight during at least one time period in adult life was associated with an increased risk of diabetes, compared to those who were never overweight. While there was no age at which being overweight was particularly detrimental, the risk associated with being overweight was cumulative across the lifecourse. CONCLUSIONS: Being overweight at any point during life is associated with an increased risk of adult-onset diabetes. The cumulative nature of this association reinforces the need to prevent the development of excess weight at an early age to reduce diabetes prevalence in coming decades.

Acne in adolescence and cause-specific mortality: lower coronary heart disease but higher prostate cancer mortality: the Glasgow Alumni Cohort Study.

Androgen level or androgen activity is implicated in several health outcomes, but its independent role remains controversial. This study investigated the association between history of acne in young adulthood, a marker of hormone activity, and cause-specific mortality in the Glasgow Alumni Cohort Study. Male students who attended Glasgow University between 1948 and 1968 and participated in voluntary health checks reported history of acne (n = 11,232). Vital status has been traced, and risk factors in adulthood are known for about 50% of the participants. Those with a history of acne were more often nonsmokers while university students and tended to be from a lower socioeconomic position. The two groups did not differ in other adolescent (height, body mass index, blood pressure, and number of siblings) or in most adult risk factors. Students who reported a history of acne had a lower risk of all-cause (hazard ratio = 0.89, 95% confidence interval (CI): 0.76, 1.04) and coronary heart disease (hazard ratio = 0.67, 95% CI: 0.48, 0.94) mortality but had some evidence of a higher risk of prostate cancer mortality (hazard ratio = 1.67, 95% CI: 0.79, 3.55). This study shows that androgen activity during adolescence may protect against coronary heart disease but confer a higher risk of prostate cancer mortality.

Measuring the habitat as an indicator of socioeconomic position: methodology and its association with hypertension.

STUDY OBJECTIVES: (1) to develop an indicator of socioeconomic position based on the social standing of the habitat (SSH), that is, the residential building, its immediate surroundings, and local neighbourhood; (2) to assess the relation of SSH to two usual markers of socioeconomic position (education and occupation) and a known, socially determined health outcome (hypertension). DESIGN: Population survey measuring SSH, detailed educational and occupational histories, and blood pressure. The SSH is a standardised assessment of the external and internal aspects of someone's building (or house), and of the characteristics of its immediate surroundings and local neighbourhood. SETTING: A sample of participants to the Bus Santé survey between 1993 and 1998, in Geneva, Switzerland. PARTICIPANTS: 588 men and women, aged 35 to 74. MAIN RESULTS: The SSH index was highly reproducible (kappa=0.8). Concordance of SSH with education or occupation was good for people of either high or low socioeconomic position, but not for those with medium education and/or occupation. There was a higher prevalence of hypertension in the lowest compared with the highest groups, defined on the basis of education or occupation, but the SSH was the only indicator that showed a higher prevalence of hypertension among people in the middle of the social spectrum. CONCLUSIONS: People of medium education or occupation are heterogeneous with respect to their habitat. Those living in habitats of medium social standing may be most affected by hypertension but this association could not be revealed on the basis of education and occupation alone. The habitat seems to capture different aspects of the socioeconomic position compared with the usual indicators of social class.

Influence of occupational exposure to latex on the prevalence of sensitization and allergy to latex in a Swiss hospital.

BACKGROUND: Replacement of powdered latex gloves has been recommended in order to prevent the development of latex allergy in health care workers. The conclusion that occupational exposure to latex gloves represents a risk factor for latex allergy is mainly based on studies without exposure controls. Atopy is also thought to be a risk factor for the development of latex allergy. OBJECTIVE: To determine the prevalence of atopy, sensitization to latex, and symptoms following latex exposure in professionally exposed and nonexposed hospital personnel by means of a cross-sectional study. METHODS: Six hundred randomly sampled individuals working in medicine and surgery departments and in surgery theaters and 300 sex- and age-matched individuals classified as administrative personnel were selected from the employee data base of the Geneva University Hospital. A questionnaire about exposure to latex and symptoms following this exposure was sent to all individuals. Skin prick test reactions and serum IgE to latex as well as standard environmental allergens were determined in both groups. RESULTS: Respiratory and skin (local) symptoms but not objective tests of latex sensitization (positive skin prick test and specific IgE to latex) were significantly associated with occupational exposure to latex (p < 0.001). Only among atopics subjects was 15 years or more of occupational exposure associated with a significantly higher prevalence of local symptoms than among those who were exposed from 1 to 9 years (odds ratio: 3.2; 95% confidence interval: 1.6-6.5). Atopy was significantly associated with sensitization to latex (odds ratio: 10.3; 95% confidence interval: 4.0-26.6) but not with local symptoms. Tests of latex sensitization were both frequently positive, less frequently negative, resulting in low kappa values. CONCLUSION: These results support the current preventive health care recommendation to replace powdered latex gloves. In atopics, increasing years of occupational exposure increase the risk of developing latex allergy. In contrast to questionnaires about local symptoms, skin prick tests and specific serum IgE to latex are of limited value in epidemiologic studies of latex allergy.

Can the declining prevalence of left-handedness with age be due to smoking?

The objective of this study was to assess whether smoking habits can explain the decline in left-handedness prevalence with age. Subjects participating in a population-based survey (n = 3,071) in Geneva, Switzerland, completed a questionnaire on innate hand preference, current hand preference for writing and smoking habits. The prevalence of innate left-handedness in the Geneva population was 9.4% in men and 7.4% in women. There was no association between smoking and left-handedness. It is concluded that smoking is not associated with hand preference and is an unlikely cause of overmortality in left-handed subjects.

Diet and socioeconomic position: does the use of different indicators matter?

OBJECTIVES: To describe the association of diet and socioeconomic position and to assess whether two different indicators, education and occupation, independently contribute in determining diet. METHODS: A community-based random sample of men and women residents of Geneva canton, aged 35 to 74, participated in a survey of cardiovascular risk factors conducted annually since 1993. Lifetime occupational and educational history and a semi-quantitative food frequency questionnaire were obtained from 2929 men and 2767 women. RESULTS: Subjects from lower education and/or occupation consumed less fish and vegetables but more fried foods, pasta and potatoes, table sugar and beer. Iron, calcium, vitamin A and vitamin D intake were lower in the lower educational and occupational groups. Both indicators significantly contributed to determining a less healthy dietary pattern for those from low social class. The effects of education and occupation on dietary habits were usually additive and synergistic for some food groups. CONCLUSION: Assessing both education and occupation, improves the description of social class inequalities in dietary habits, as they act, most of the time, as independent factors.

The differential effect of education and occupation on body mass and overweight in a sample of working people of the general population.

PURPOSE: To assess whether two indicators of social class, education and occupation, have independent and/or synergistic effects in determining the body mass and overweight. METHODS: Body mass index (BMI), education, and occupation were assessed in a survey of 1767 men and 1268 women from a representative sample of currently working people of the general population of Geneva, Switzerland. Education and occupation were categorized as low, medium, and high. Overweight was defined as BMI > or = 25 kg/m(2). RESULTS: The prevalence of overweight was 52.1% in men and 28.7% in women. Men with overweight were more likely to have low education while women with overweight had lower education and lower occupation. Education and occupation were inversely related to BMI in both genders and, in women, had a synergistic effect (p-value for the interaction = 0.03). CONCLUSIONS: Education and occupation have independent and, in women, synergistic effects on BMI. The two indicators may express different mechanisms through which low social class is related to high body mass.

Incidence of status epilepticus in French-speaking Switzerland: (EPISTAR).

BACKGROUND: To determine the incidence, risk factors, and case fatality rate of status epilepticus (SE) in the French-speaking part of Switzerland. METHODS: Between October 1, 1997 and September 30, 1998 all cases of SE referred to all the hospitals in the six cantons of the French-speaking part of Switzerland were identified by physicians working in emergency rooms, intensive care units, and electroencephalography departments; neurologists; and pediatricians from all hospitals in the area. Each case was validated and classified according to seizure type and etiology. RESULTS: Over 1 year, 172 cases were identified, of whom 74 had a history of epilepsy (42.4%). The crude and standardized annual incidence rate were 9.9/100,000 (95% CI, 8.4 to 11.4) and 10.3/100,000 (95% CI, 8.7 to 11.9). The incidence rate was higher among children < 1 year of age and adults > 65 years, and among men than women. There were 108 cases of acute symptomatic SE (incidence: 6.2 per 1000), 49 cases of remote symptomatic SE, and 15 cases of unknown etiology. Case fatality rate was 7.6%. CONCLUSIONS: The standardized incidence rate of SE in the French-speaking part of Switzerland was lower than that reported in Rochester, MN (18.3/100,000) and in the white population of Richmond, VA (20/100,000). The discrepancy may stem from the lack of a homogeneous, rigorous, and pragmatic definition of SE and the efficient management of acute repetitive seizures in this area.

The association between switching hand preference and the declining prevalence of left-handedness with age.

OBJECTIVES: This study determined the prevalence of left-handedness and of switching hand preference among innately left-handed subjects. METHODS: Subjects of Swiss nationality (n = 1692), participating in a population-based survey in Geneva, Switzerland, completed a questionnaire on innate hand preference and current hand preference for writing. RESULTS: From 35 to 44 years of age to 65 to 74 years of age, the prevalence of innate left-handedness declined from 11.9% to 6.2% (trend P = .007). In these same age groups, the proportion of innately left-handed subjects who switched to the right hand for writing increased from 26.6% to 88.9% (trend P = .0001). CONCLUSIONS: Across generations, we found an increase in the prevalence of switching hand preference among innately left-handed subjects. This phenomenon could be explained by social and parental pressure to use the right hand.

Effect of the method of administration, mail or telephone, on the validity and reliability of a respiratory health questionnaire. The Spanish Centers of the European Asthma Study.

The European Community Respiratory Health Survey (ECRHS), a multinational survey, assesses and compares the prevalence of asthma among subjects, aged 20 to 44, in several European areas. In Spain, some participating centers have used mail and telephone as methods of questionnaire administration. The objective of the present study was to determine whether the validity and reliability of the questionnaire differed by method of administration. Reliability of the questionnaire was measured with the kappa index and the odds ratio of agreement, and validity with the sensitivity and specificity. This study found differences in the reliability of the questionnaires although these differences were more related to the questions themselves than to the method of administration. Among men, but not women, mailed questionnaires were more sensitive and telephone questionnaires more specific. We hypothesize that these differences in validity were due to the self-selection to more severe symptomatic subjects replying earlier and therefore to the mailed questionnaire. Combining different methods of administration was useful as it increased participation and was an adequate procedure to obtain information of good quality.