Metabolically healthy obesity across the life course: epidemiology, determinants and implications

In recent years, different subphenotypes of obesity have been described, including metabolically healthy obesity (MHO), in which a proportion of obese individuals, despite excess body fat, remain free of metabolic abnormalities and increased cardiometabolic risk. In the absence of a universally accepted set of criteria to classify MHO, the reported prevalence estimates vary widely. Our understanding of the determinants and stability of MHO over time and the associated cardiometabolic and mortality risks is improving, but many questions remain. For example, whether MHO is truly benign is debatable, and whether risk stratification of obese individuals on the basis of their metabolic health status may offer new opportunities for more personalized approaches in diagnosis, intervention, and treatment of diabetes remains speculative. Furthermore, as most of the research to date has focused on MHO in adults, little is known about childhood MHO. In this review, we focus on the epidemiology, determinants, stability, and health implications of MHO across the life course.

Risk factors across the life course and dementia in a Brazilian population: results from the Sao Paulo Ageing & Health Study (SPAH)

Background Several mechanisms have been suggested to explain the association between adversities across life and dementia. This study aimed to investigate the association between indicators of socioeconomic disadvantages throughout the life-course and dementia among older adults in Sao Paulo, Brazil and to explore possible causal pathways. Methods We used baseline data from the SPAH study which involved participants aged 65 years and older (n = 2005). The outcome of interest was prevalent dementia. Exposures included in the analyses were socioeconomic position (SEP) indicators in childhood (place of birth and literacy) and adulthood (occupation and income), anthropometric measurements as markers of intrauterine and childhood environment (head circumference and leg length), smoking, diabetes and hypertension. Logistic regression models were used to test the hypothesized pathways and to assess whether there was an association between cumulative adversities across the life course and prevalent dementia. Results Indicators of socioeconomic disadvantage in early life were associated with increased prevalence of dementia. This association was partially mediated through adulthood SEP. Head circumference and leg length were also clearly associated with dementia but there was no evidence that this association was mediated by early life socioeconomic disadvantage. There was an association between cumulative unfavourable conditions across the life course and dementia. Conclusions Early life disadvantages seem to operate through biological mechanisms associated with passive brain reserve and opportunities in life representing active cognitive reserve. Prevention of dementia should start early in life and continue through life span as seen with many other chronic diseases.

Examining life-course influences on chronic disease: the importance of birth cohort studies from low- and middle- income countries. An overview

The objectives of this overview are to describe the past and potential contributions of birth cohorts to understanding chronic disease aetiology; advance a justification for the maintenance of birth cohorts from low- and middle-income countries (LMIC); provide an audit of birth cohorts from LMIC; and, finally, offer possible future directions for this sphere of research. While the contribution of birth cohorts from affluent societies to understanding disease aetiology has been considerable, we describe several reasons to anticipate why the results from such studies might not be directly applied to LMIC. More than any other developing country, Brazil has a tradition of establishing, maintaining and exploiting birth cohort studies. The clear need for a broader geographical representation may be precipitated by a greater collaboration worldwide in the sharing of ideas, fieldwork experience, and cross-country cohort data comparisons in order to carry out the best science in the most efficient manner. This requires the involvement of a central overseeing body - such as the World Health Organization - that has the respect of all countries and the capacity to develop strategic plans for `global' life-course epidemiology while addressing such issues as data-sharing. For rapid progress to be made, however, there must be minimal bureaucratic entanglements.

Association between growth and blood pressure during the life course in children and adolescents

Background: Little is known on the relative importance of growth at different periods between birth and adolescence on blood pressure (BP). Objective: To assess the association between birth weight, change in body weight (growth) and BP across the entire span of childhood and adolescence. Methods: School-based surveys were conducted annually between 1998 and 2006 among all children in four school grades (kindergarten, 4th, 7th, and 10th year of compulsory school) in the Seychelles, Indian Ocean. Height and weight and BP were measured. Three cohorts of children examined twice were analyzed: 1606 children surveyed at age 5.5 and 9.1, 2557 at age 9.2 and 12.5, and 2065 at age 12.5 and 15.5, respectively. Weights at birth and at one year were extracted from medical files. Weights were expressed as Z-scores and growth was defined as a change in weight Z-scores (corresponding to weight centile crossing). The association between BP (at age 5.5, 9.2, 12.5, and 15.5) and weight at different times was assessed by linear regression. Using results of regression models of BP on all successive weights, life course plots were drawn by plotting regression coefficients against age at which weight was measured. The figure shows a life course plot of systolic BP in boys aged 15.5. Results: Without adjustment for current weight (at the time of BP measurement), birth weight was not associated with current BP, irrespective of age, excepted for girls at age 15.5 for whom a modest positive association was found. When adjusted for current weight, birth weight was negatively and modestly associated with current BP. BP was strongly associated with current weight, irrespective of age. Life course plots showed that BP was strongly associated with growth during the few preceding years but not with growth during earlier years, except for growth during the first year of life which tended to be associated with systolic BP. Conclusions: Our findings suggest that BP during childhood and adolescence is mainly determined by current body weight and recent growth.

Life-course socioeconomic status and DNA methylation of genes regulating inflammation

BACKGROUND: In humans, low socioeconomic status (SES) across the life course is associated with greater diurnal cortisol production, increased inflammatory activity and higher circulating antibodies for several pathogens, all suggesting a dampened immune response. Recent evidence suggests that DNA methylation of pro-inflammatory genes may be implicated in the biological embedding of the social environment. METHODS: The present study examines the association between life-course SES and DNA methylation of candidate genes, selected on the basis of their involvement in SES-related inflammation, in the context of a genome-wide methylation study. Participants were 857 healthy individuals sampled from the EPIC Italy prospective cohort study. RESULTS: Indicators of SES were associated with DNA methylation of genes involved in inflammation. NFATC1, in particular, was consistently found to be less methylated in individuals with low vs high SES, in a dose-dependent manner. IL1A, GPR132 and genes belonging to the MAPK family were also less methylated among individuals with low SES. In addition, associations were found between SES and CXCL2 and PTGS2, but these genes were consistently more methylated among low SES individuals. CONCLUSIONS: Our findings support the hypothesis that the social environment leaves an epigenetic signature in cells. Although the functional significance of SES-related DNA methylation is still unclear, we hypothesize that it may link SES to chronic disease risk.

Examining life-course influences on chronic disease: the Ribeirão Preto and São Luís birth cohort studies (Brazil)

More than any other low- and middle-income country, Brazil has the longest research tradition of establishing, maintaining and exploiting birth cohort studies. This research pedigree is highlighted in the present issue of the Brazilian Journal of Medical and Biological Research, which contains a series of twelve papers from the Ribeirão Preto and São Luis birth cohort studies from the Southeast and Northeast of Brazil, respectively. The topics covered in this raft of reports vary and include predictors of perinatal health and maternal risk factors, early life determinants of cardiovascular risk factors in childhood and adolescence, use of health services, and a description of dietary characteristics of young adults, amongst other topics. There is also a guide to the background, objectives, sampling and protocols employed across these studies, which, together with similar pieces published in past issues of the Brazilian Journal, serve as a very useful starting point, particularly for potential collaborators. In the fervent hope that further follow-up of these cohorts will take place - we provide our own justification for cohort maintenance and extension in this issue - future data collection could include: genetic material, atherosclerosis, ascertained, for instance, by intima-media thickness, and IQ testing in children - scores from which are emerging as potentially important predictors of adult health outcomes up to six decades later.

Early life course determinants of young adults' gambling behaviour. An Australian Longitudinal Study

Problem gambling represents a public concern as both a social and health issue. Available evidence shows problem gambling is associated with a range of psychological disorders, criminality, and disruption to families. While gambling itself may represent a pleasurable pursuit for the majority, for a proportion, gambling-related activities may assume many of the characteristics of an addiction and have the capacity to undermine individuals� mental and physical health, social relationships, financial independence, as well as the financial and psychological wellbeing of their families and/or friends. The objectives of this study are based on the need to increase our understanding of gambling behaviour, its antecedents, as well its influence on the health and wellbeing of gamblers and their families. One of the most important and unresolved issues in gambling research is whether the mental health and social/family correlates of gambling precede or follow gambling behaviour. This report focuses on this issue.

The Life Course Determinants of Vulnerability in Late Careers

Late career is often seen as a more vulnerable life-stage in the labour market, in which workers may experience a deterioration in job quality. Using a life course perspective and longitudinal data, this article analyses the vulnerability associated with late career by focusing on four occupational dimensions: working-time, career continuity, retirement timing and income change. The research is carried out using data from Switzerland, a country where the age profile of the labour force is an increasing issue. The paper also adopts a cumulative disadvantage perspective to examine the impact of previous work and family life experiences on work life vulnerability at older age. Our data come from the Survey of Health, Ageing and Retirement in Europe (SHARELIFE). The paper uses cluster analysis, sequence analysis and ordered logistic regression. Results show that women with previous family responsibilities resulting in long-term unemployment or caring, often with health complications, are more likely to be vulnerable to deterioration in job quality in late career. This suggests that experiences in the last period of the working life may be just as gendered as earlier periods.

Who benefits from parental leave in Spain? : a life course analysis

This paper analyses the extent to which individual and workplacecharacteristics and regional policies influence the use and duration ofparental leave in Spain. The research is based on a sample of 125,165people, and 6,959 parental leaves stemming from the ‘Sample ofWorking Life Histories’ (SWLH), 2006. The SWLH consists of administrative register data which include information from threedifferent sources: Social Security, Municipality and Income TaxRegisters. We adopt a simultaneous equations approach to analyse theuse (logistic regression) and duration (event history analysis) ofparental leave, which allows us to control for endogeneity and censoredobservations. We argue that the Spanish parental leave scheme increases gender and social inequalities insofar as reinforces genderrole specialization, and only encourages the reconciling of work andfamily life among workers with a good position in the labour market(educated employees with high and stable working status).

Sustainable and equitable retirement in a life course perspective

We argue that long term sustainability of social security systems requires not only better equilibrium between the proportion in retirement and in employment but also an equitable distribution of the additional financial burden that aging inevitably will require. We examine how a proportional fixed ratios model of burden sharing between the aged and non-aged will establish inter-generational equity. Additionally we address the question of intra-generational equity and argue that the positive association between lifetime income and longevity requires more progressive financing of pensions and of care for the elderly.