Socioeconomic Factors and All Cause and Cause-Specific Mortality among Older People in Latin America,India, and China: A Population-Based Cohort Study

Background

Even in low and middle income countries most deaths occur in older adults. In Europe, the effects of better education and home ownership upon mortality seem to persist into old age, but these effects may not generalise to LMICs. Reliable data on causes and determinants of mortality are lacking.

Methods and Findings

The vital status of 12,373 people aged 65 y and over was determined 3–5 y after baseline survey in sites in Latin America, India, and China. We report crude and standardised mortality rates, standardized mortality ratios comparing mortality experience with that in the United States, and estimated associations with socioeconomic factors using Cox''s proportional hazards regression. Cause-specific mortality fractions were estimated using the InterVA algorithm. Crude mortality rates varied from 27.3 to 70.0 per 1,000 person-years, a 3-fold variation persisting after standardisation for demographic and economic factors. Compared with the US, mortality was much higher in urban India and rural China, much lower in Peru, Venezuela, and urban Mexico, and similar in other sites. Mortality rates were higher among men, and increased with age. Adjusting for these effects, it was found that education, occupational attainment, assets, and pension receipt were all inversely associated with mortality, and food insecurity positively associated. Mutually adjusted, only education remained protective (pooled hazard ratio 0.93, 95% CI 0.89–0.98). Most deaths occurred at home, but, except in India, most individuals received medical attention during their final illness. Chronic diseases were the main causes of death, together with tuberculosis and liver disease, with stroke the leading cause in nearly all sites.

Conclusions

Education seems to have an important latent effect on mortality into late life. However, compositional differences in socioeconomic position do not explain differences in mortality between sites. Social protection for older people, and the effectiveness of health systems in preventing and treating chronic disease, may be as important as economic and human development. Please see later in the article for the Editors'' Summary     

Characterization of a heat-shock-inducible hsp70 gene of the green alga Volvox carteri

The green alga Volvox carteri possesses several thousand cells, but just two cell types: large reproductive cells called gonidia, and small, biflagellate somatic cells. Gonidia are derived from large precursor cells that are created during embryogenesis by asymmetric cell divisions. The J domain protein GlsA (Gonidialess A) is required for these asymmetric divisions and is believed to function with an Hsp70 partner. As a first step toward identifying this partner, we cloned and characterized V. carteri hsp70A, which is orthologous to HSP70A of the related alga Chlamydomonas reinhardtii. Like HSP70A, V. carteri hsp70A contains multiple heat shock elements (HSEs) and is highly inducible by heat shock. Consistent with these properties, Volvox transformants that harbor a glsA antisense transgene that is driven by an hsp70A promoter fragment express Gls phenotypes that are temperature-dependent. hsp70A appears to be the only gene in the genome that encodes a cytoplasmic Hsp70, so we conclude that Hsp70A is clearly the best candidate to be the chaperone that participates with GlsA in asymmetric cell division.     

The role of GlsA in the evolution of asymmetric cell division in the green alga<Emphasis Type="Italic"> Volvox carteri</Emphasis>

Volvox carteri, a green alga in the order Volvocales, contains two completely differentiated cell types, small motile somatic cells and large reproductive cells called gonidia, that are set apart from each other during embryogenesis by a series of visibly asymmetric cell divisions. Mutational analysis has revealed a class of genes (gonidialess, gls) that are required specifically for asymmetric divisions in V. carteri, but that are dispensable for symmetric divisions. Previously we cloned one of these genes, glsA, and showed that it encodes a chaperone-like protein (GlsA) that has close orthologs in a diverse set of eukaryotes, ranging from fungi to vertebrates and higher plants. In the present study we set out to explore the role of glsA in the evolution of asymmetric division in the volvocine algae by cloning and characterizing a glsA ortholog from one of the simplest members of the group, Chlamydomonas reinhardtii, which does not undergo asymmetric divisions. This ortholog (which we have named gar1, for glsA related) is predicted to encode a protein that is 70% identical to GlsA overall, and that is most closely related to GlsA in the same domains that are most highly conserved between GlsA and its other known orthologs. We report that a gar1 transgene fully complements the glsA mutation in V. carteri, a result that suggests that asymmetric division probably arose through the modification of a gene whose product interacts with GlsA, but not through a modification of glsA itself.     

Abdominal Tubercles of Adult Male Camel Crickets, Pristoceuthophilus marmoratus Rehn (Orthoptera: Rhaphidophoridae), Produce Cues Attractive to Females

In contrast to many crickets and katydids, adult male camel crickets (Orthoptera: Raphidophoridae) do not stridulate and do not produce audible air-borne calling songs to attract females for mating. The mating behavior of most camel cricket species is undescribed; how pair-formation occurs is unknown, but chemical cues seem one likely possibility. In the camel cricket Pristoceuthophilus marmoratus Rehn, we test (1) the role of chemical cues in conspecific attraction, and (2) the role of the abdominal tubercles of adult males in producing those cues. We show (1) that virgin adult females are attracted to paper towels previously exposed to adult males, and (2) that paper towels previously exposed to adult males with exposed tubercles are more attractive than paper towels previously exposed to adult males with experimentally closed tubercles. In addition, we present Scanning Electron Microscope photos of adult male tubercle structure that are consistent with their putative role in producing chemical cues.