Biomedical subjects

Burton H Singer

Publications and source records attributed to Burton H Singer.

40 records · Page 3Linked to original sources

PubMed2002

The potential of intermittent irrigation for increasing rice yields, lowering water consumption, reducing methane emissions, and controlling malaria in African rice fields.

Rice production in sub-Saharan Africa has more than doubled in the last 3 decades and the potential to further develop rice-harvested areas is considerable. Several studies have demonstrated that the transformation of arable land into rice irrigation might create suitable habitats for large populations of disease vectors. Prominent among those are anopheline mosquitoes responsible for transmission of malaria. The method of irrigation on an intermittent basis during the rice-cropping calendar has gained renewed interest as a potentially effective malaria control strategy since the early 1980s. We review the experiences of the past 80 years with intermittent irrigation in the cultivation of rice. This method has been shown to reduce significantly the density of malaria vectors by curtailing their larval development. Furthermore, reduced methane emissions and water savings with at least equal yields were achieved in intermittently irrigated rice fields. We explore and discuss under what conditions intermittent irrigation might be beneficial in new rice-growing areas and identify steps that have to be taken to expand such programs in the future.

Africa South of the Sahara↗

PubMedDate not supplied

Social relationships, gender, and allostatic load across two age cohorts.

OBJECTIVE: This article addresses the question of biological pathways through which social integration and support may affect morbidity and mortality risks. A new concept of cumulative biological risk, allostatic load, is used to test the hypothesis that social experiences affect a range of biological systems. Data from two community-based cohorts are examined to evaluate the consistency of findings across two different age groups. METHODS: One cohort included older adults aged 70 to 79 years (N = 765); the other cohort included persons aged 58 to 59 years (N = 106). Allostatic load was assessed using identical protocols in the two cohorts. Measures of social experience were similar but not identical, reflecting levels of social integration and support for the older cohort vs. childhood and adult experiences of loving/caring relationships with parents and spouse for the younger cohort. Gender-specific analyses were examined to evaluate possible gender differences in patterns of association. RESULTS: In the younger cohort, positive cumulative relationship experiences were associated with lower allostatic load for men and women. In the older cohort, men who were more socially integrated and those reporting more frequent emotional support from others had lower allostatic load scores; similar but nonsignificant associations were seen for women. CONCLUSIONS: Evidence from two cohorts provides support for the hypothesis that positive social experiences are associated with lower allostatic load. These findings are consistent with the hypothesis that social experiences affect a range of biological systems, resulting in cumulative differences in risks that in turn may affect a range of health outcomes.

Aged↗

PubMedDate not supplied

Lifelong menstrual histories are typically erratic and trending: a taxonomy.

OBJECTIVE: Menstrual cycles are composites of complex events; the data describing them are correspondingly rich. We seek to quantitatively represent menstrual histories from menarche to menopause and to evaluate the clinical belief that regular and stable cycle lengths are the most normative histories. DESIGN: Using prospective data from the Tremin Trust, we classified the menstrual histories of 628 women as very stable (type I), stable but with greater variability in cycle lengths (type II), oscillating and erratic with a downward trend in cycle length (type III), oscillating and erratic with no downward trend in cycle length (type IV), or highly erratic and variable (type V). Classification criteria were created by examining basic summary statistics of menstrual cycle lengths. Specifically, we identified key features describing variability of median cycle length, the mean of the interquartile range, the consistency of the interquartile range, the slope of median cycle lengths, and the number of stable 5-year intervals between ages 15 and 45+. RESULTS: We present the first characterization of full menstrual histories. Our taxonomy captures the essential features of menstrual bleeding patterns for a heterogeneous population. Persistently stable histories (types I and II) were seen in only 28% of the women; erratic histories (types III through V) characterized 72%. When examining all participants, significant differences were seen in age at menarche (P < 0.05), age at menopause (P < 0.01), and number of births (P < 0.01) between these stable and erratic groups. CONCLUSIONS: Although clinicians have traditionally thought of "normal" menstrual histories as being regular and stable, the distribution of women in our five categories suggest that variable histories are most common. Clinically, these results may suggest the need for a paradigm shift in what gynecologists view as normal and abnormal menstrual cycle histories.

Algorithms↗

PubMedDate not supplied

Reduction in allostatic load in older adults is associated with lower all-cause mortality risk: MacArthur studies of successful aging.

OBJECTIVES: To study the association between change in allostatic load (a risk score constructed from multiple biological markers) over a 2.5-year period and mortality in the following 4.5 years in older adults. METHODS: We measured 10 physiologic parameters at baseline (1988) in a cohort of 171 high-functioning, community-dwelling, 70- to 79-year-old adults. These measurements were repeated 2.5 years later, in 1991. Summary allostatic load scores for 1988 and 1991 were created as the weighted sum of the 10 biological markers and their second-order terms. Mortality status (alive or dead) for participants was determined 4.5 years later, in 1995. The association between change in allostatic load score (1988-1991) and subsequent mortality (1991-1995) was studied using logistic regression. RESULTS: Compared with participants whose allostatic load score decreased between 1988 and 1991, individuals whose allostatic load score increased had higher risk of all-cause mortality between 1991 and 1995 (15% versus 5%, p = .047). Adjusted for age and baseline allostatic load, each unit increment in the allostatic load change score was associated with mortality odds ratio of 3.3 (95% confidence interval, 1.1-9.8). CONCLUSION: Our results suggest that even in older ages, change in risk scores can be followed to improve assessment of mortality risk.

Aged↗