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In this article we argue for the utility of the life-course perspective as a tool for understanding and addressing health disparities across socioeconomic and racial or ethnic groups, particularly disparities that originate in childhood. Key concepts and terms used in life-course research are briefly defined; as resources, examples of existing literature and the outcomes covered are provided along with examples of longitudinal databases that have often been used for life-course research. The life-course perspective focuses on understanding how early-life experiences can shape health across an entire lifetime and potentially across generations; it systematically directs attention to the role of context, including social and physical context along with biological factors, over time. This approach is particularly relevant to understanding and addressing health disparities, because social and physical contextual factors underlie socioeconomic and racial/ethnic disparities in health. A major focus of life-course epidemiology has been to understand how early-life experiences (particularly experiences related to economic adversity and the social disadvantages that often accompany it) shape adult health, particularly adult chronic disease and its risk factors and consequences. The strong life-course influences on adult health could provide a powerful rationale for policies at all levels--federal, state, and local--to give more priority to investment in improving the living conditions of children as a strategy for improving health and reducing health disparities across the entire life course.

SUMMARY Eastern Sierra Nevada populations of the willow beetle Chrysomela aeneicollis commonly experience stressfully high and low environmental temperatures that may influence survival and reproduction. Allele frequencies at the enzyme locus phosphoglucose isomerase (PGI) vary across a climatic latitudinal gradient in these populations, with PGI allele 1 being most common in cooler regions and PGI allele 4 in warmer ones. PGI genotypes differ in heat and cold tolerance and in expression of a 70 kDa heat shock protein. Here we examine genetic, behavioral and environmental factors affecting a performance character, running speed, for willow beetles, and assess effects of consecutive cold and heat exposure on running speed and expression of Hsp70 in the laboratory. In nature, running speed depends on air temperature and is higher for males than females. Mating beetles ran faster than single beetles, and differences among PGI genotypes in male running speed depended on the presence of females. In the laboratory, exposure to cold reduced subsequent running speed, but the amount of this reduction depended on PGI genotype and previous thermal history. Effects of exposure to heat also depended on life history stage and PGI genotype. Adults possessing allele 1 ran fastest after a single exposure to stressful temperature, whereas those possessing allele 4 ran faster after repeated exposure. Larvae possessing allele 4 ran fastest after a single stressful exposure, but running speed generally declined after a second exposure to stressful temperature. The ranking of PGI genotypes after the second exposure depended on whether a larva had been exposed to cold or heat. Effects of temperature on Hsp70 expression also varied among PGI genotypes and depended on type of exposure, especially for adults (single heat exposure, two cold exposures: PGI 1-1>1-4>4-4;other multiple extreme exposures: 4-4>1-4>1-1). There was no consistent association between alleles at other polymorphic enzyme loci and running speed or Hsp70 expression. These data suggest that variation at PGI is associated with considerable plasticity in running speed. Differences in Hsp70 expression among PGI genotypes suggest that the heat-shock response may buffer differences in thermal tolerance and performance among genotypes and help maintain the PGI polymorphism in a thermally variable environment.

BACKGROUND: Systematic reviews for the US Preventive Services Task Force have found less high-quality evidence on psychological than physical harms of screening. To understand the extent of evidence on psychological harms, we developed an evidence map that quantifies the distribution of evidence on psychological harms for five adult screening services. We also note gaps in the literature and make recommendations for future research. METHODS: We systematically searched PubMed, PsycInfo, and CINAHL from 2002 to 2012 for studies of any research design that assessed the burden or frequency of psychological harm associated with screening for: prostate and lung cancers, osteoporosis, abdominal aortic aneurysm (AAA) and carotid artery stenosis (CAS). We also searched for studies that estimated rates of overdiagnosis (a marker for unnecessary labeling). We included studies published in English and used dual independent review to determine study inclusion and to abstract information on design, types of measures, and outcomes assessed. RESULTS: Sixty-eight studies assessing psychological harms met our criteria; 62 % concerned prostate cancer and 16 % concerned lung cancer. Evidence was scant for the other three screening services. Overall, only about one-third of the studies used both longitudinal designs and condition-specific measures (ranging from 0 % for AAA and CAS to 78 % for lung cancer), which can provide the best evidence on harms. An additional 20 studies that met our criteria estimated rates of overdiagnosis in lung or prostate cancer. No studies estimated overdiagnosis for the non-cancer screening services. DISCUSSION: Evidence on psychological harms varied markedly across screening services in number and potential usefulness. We found important evidence gaps for all five screening services. The evidence that we have on psychological harms is inadequate in number of studies and in research design and measures. Future research should focus more clearly on the evidence that we need for decision making about screening.