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Biomedical subjects

J C Caldwell

Publications and source records attributed to J C Caldwell.

At least 19 recordsLinked to original sources
PubMed2001

Demographers and the study of mortality: scope, perspectives, and theory.

Demographers have for a long time adopted an empirical approach to the study of the levels and trends of mortality, fertility, and population size. They depend for their analyses on data, usually collected until recent times by government and often for other purposes. Modern demography had its origins in Britain in the second half of the seventeenth century. The major focus of demographers has usually been on mortality, although fertility studies predominated in the 1960s and 1970s. Mortality decline in the West only became certain in the late nineteenth century. Until the 1960s the fastest mortality declines were for the young, but an unheralded mortality decline among the old thereafter became important. The world, especially in economically advanced countries, is faced with an increasingly high proportion of old people, explained largely, not by mortality decline, but by fertility decline. Explanations for the mortality transition place different emphases on the role of modern medicine, better nutrition, and behavioral and social change, particularly rising levels of education. Even among the old, at least until 85 years of age, there are wide differentials in mortality by educational level. Analysts have divided the mortality transition into stages: (1) high, pretransitional mortality, (2) early transitional mortality with the decline explained by the conquest of infectious disease, and (3) late transitional mortality largely attributable to degenerative disease. Some have now added stage (4), the reduction or delay in death from degenerative causes. Attempts have been made to effect the convergence of demographic and epidemiological approaches to the analysis of mortality, and they have been more successful in the case of medical demographic than in social demographic approaches.

Adult↗
PubMed2000

Air toxics and health risks in California: the public health implications of outdoor concentrations.

Of the 188 hazardous air pollutants (HAPs) listed in the Clean Air Act, only a handful have information on human health effects, derived primarily from animal and occupational studies. Lack of consistent monitoring data on ambient air toxics makes it difficult to assess the extent of low-level, chronic, ambient exposures to HAPs that could affect human health, and limits attempts to prioritize and evaluate policy initiatives for emissions reduction. Modeled outdoor HAP concentration estimates from the U.S. Environmental Protection Agency's Cumulative Exposure Project were used to characterize the extent of the air toxics problem in California for the base year of 1990. These air toxics concentration estimates were used with chronic toxicity data to estimate cancer and noncancer hazards for individual HAPs and the risks posed by multiple pollutants. Although hazardous air pollutants are ubiquitous in the environment, potential cancer and noncancer health hazards posed by ambient exposures are geographically concentrated in three urbanized areas and in a few rural counties. This analysis estimated a median excess individual cancer risk of 2.7E-4 for all air toxics concentrations and 8600 excess lifetime cancer cases, 70% of which were attributable to four pollutants: polycyclic organic matter, 1,3 butadiene, formaldehyde, and benzene. For noncancer effects, the analysis estimated a total hazard index representing the combined effect of all HAPs considered. Each pollutant contributes to the index a ratio of estimated concentration to reference concentration. The median value of the index across census tracts was 17, due primarily to acrolein and chromium concentration estimates. On average, HAP concentrations and cancer and noncancer health risks originate mostly from area and mobile source emissions, although there are several locations in the state where point sources account for a large portion of estimated concentrations and health risks. Risk estimates from this study can provide guidance for prioritizing research, monitoring, and regulatory intervention activities to reduce potential hazards to the general population. Improved ambient monitoring efforts can help clarify uncertainties inherent in this analysis.

Acrolein↗
PubMed1998

The construction of adolescence in a changing world: implications for sexuality, reproduction, and marriage.

This article aims to show how the period now known as adolescence came into being and how it was shaped by international economic, institutional, and social influences. It considers premodern societies and argues that traditional culture has shaped contemporary adolescence even more than has global society. Explanations are offered for the enormous differences across the world in adolescent sexuality, reproduction, and marriage. The data are drawn mainly from research programs in Nigeria, Sri Lanka, India, and Bangladesh, and comparisons are made with other countries.

Adolescent↗
PubMed1997

Male and female circumcision in Africa from a regional to a specific Nigerian examination.

There is a strong relationship between male and female circumcision in traditional thought and, north of the equator, in their practice by ethnic groups. The Southwest Nigeria Study, a 1994-95 survey of 1749 males and 1976 females in Nigeria's Ondo, Oyo and Lagos States, is used to examine contemporary levels of circumcision, reasons for carrying out the practice, and the circumstances of the circumcision operations. These findings are compared with earlier southwest Nigerian and West African studies. The persistence of the practices is confirmed, but rapid change towards their medicalization is also established. Possible links with AIDS are discussed.

Africa↗
PubMed1997

Perceived male sexual needs and male sexual behaviour in southwest Nigeria.

Part of a research programme studying methods of combating the AIDS epidemic was a survey and accompanying qualitative research focused on attitudes toward male sexuality and male sexual behaviour outside marriage and the extent and success of female attempts to control it. A survey of 1749 males and 1976 females was conducted in urban and rural populations in three states of southwest Nigeria. The majority of the community believes that males are by nature sexually polygynous, although about half the community believes that male sexuality can and should be confined to marriage. These beliefs arise out of the nature of the traditional society and are being changed by new ways of life, education and imported religions. Nevertheless, sufficiently rapid change is unlikely, even if promoted by government, to successfully combat a major AIDS epidemic, and the major strategy should attempt to reduce the rate of transmission, especially in high-risk relationships.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Cell recruitment to the sperm granuloma which follows vasectomy in the rat.

Sperm granulomas are chronic inflammatory lesions at sites of extravasation of spermatozoa from the reproductive tract. Using light and transmission electron microscopy, monocytes were identified in the wall of the early granuloma of the vasectomized rat. Some young macrophages contained sperm fragments and scanning electron microscopy showed them to wrap around, and partially engulf, spermatozoa. T-lymphocytes predominated over B-lymphocytes in the granuloma wall, helper cells being more numerous than suppressor/cytotoxic cells. The percentage of lymphocytes of all classes among the cells of the granuloma wall was higher at 3 months than at 3 weeks and 6 months after vasectomy, reflecting the high immunological activity known to occur at this interval after vasectomy in the rat.

Animals↗
PubMed1996

The African AIDS epidemic.

In parts of sub-Saharan Africa, nearly 25 percent of the population is HIV-positive as a result of heterosexual transmission of the virus. Could lack of circumcision make men in this region particularly susceptible?

Acquired Immunodeficiency Syndrome↗