Maximum entropy and the state-variable approach to macroecology.

The biodiversity scaling metrics widely studied in macroecology include the species-area relationship (SAR), the scale-dependent species-abundance distribution (SAD), the distribution of masses or metabolic energies of individuals within and across species, the abundance-energy or abundance-mass relationship across species, and the species-level occupancy distributions across space. We propose a theoretical framework for predicting the scaling forms of these and other metrics based on the state-variable concept and an analytical method derived from information theory. In statistical physics, a method of inference based on information entropy results in a complete macro-scale description of classical thermodynamic systems in terms of the state variables volume, temperature, and number of molecules. In analogy, we take the state variables of an ecosystem to be its total area, the total number of species within any specified taxonomic group in that area, the total number of individuals across those species, and the summed metabolic energy rate for all those individuals. In terms solely of ratios of those state variables, and without invoking any specific ecological mechanisms, we show that realistic functional forms for the macroecological metrics listed above are inferred based on information entropy. The Fisher log series SAD emerges naturally from the theory. The SAR is predicted to have negative curvature on a log-log plot, but as the ratio of the number of species to the number of individuals decreases, the SAR becomes better and better approximated by a power law, with the predicted slope z in the range of 0.14-0.20. Using the 3/4 power mass-metabolism scaling relation to relate energy requirements and measured body sizes, the Damuth scaling rule relating mass and abundance is also predicted by the theory. We argue that the predicted forms of the macroecological metrics are in reasonable agreement with the patterns observed from plant census data across habitats and spatial scales. While this is encouraging, given the absence of adjustable fitting parameters in the theory, we further argue that even small discrepancies between data and predictions can help identify ecological mechanisms that influence macroecological patterns.

Prostate cancer: demographic and behavioral correlates of stage at diagnosis among blacks and whites in North Carolina.

OBJECTIVES: Although stage at diagnosis is one of the most important predictors of survival from prostate cancer, demographic factors, screening practices, and knowledge and beliefs associated with stage at diagnosis have not been well documented, particularly by race. METHODS: We conducted telephone interviews with 117 black and 114 white men diagnosed with prostate cancer to identify the demographic factors, healthcare-seeking behaviors, and prostate cancer-related knowledge, attitudes, and practices associated with stage. The sample was stratified by stage at diagnosis and was composed of men 50 to 74 years old who resided in a contiguous 63-county region in North Carolina and who were diagnosed at 1 of 16 participating hospitals. RESULTS: Among blacks, stage was inversely correlated with income (P = 0.04) and health insurance status (P < or = 0.001); among whites, stage was not associated with income or health insurance status, but approached significance with marital status (P = 0.06). Awareness of prostate cancer before diagnosis tended to decline with advancing stage among black men (P = 0.07), but was high for all stages (greater than 93%) among whites. Report of a prostate-specific antigen screen was inversely correlated with stage among black men (P = 0.01); a trend was observed among whites but was not significant (P = 0.20). Knowledge of prostate cancer risk factors was not significantly associated with stage for blacks or whites. Less than one third of men in each race and stage group knew that black men are at increased risk of prostate cancer. CONCLUSIONS: Demographic and other factors vary with stage and should be considered when designing and targeting interventions to reduce late diagnosis of prostate cancer.

Treatment options, selection, and satisfaction among African American and white men with prostate carcinoma in North Carolina.

BACKGROUND: In the U.S., prostate carcinoma mortality is greatest among African Americans. In North Carolina, the state with the fourth largest population of African Americans, the prostate carcinoma mortality rate is 2.5 times greater among African Americans than among whites and is the highest reported rate for any state in the nation. To explore potential reasons for the racial differential in mortality, a study was undertaken to determine whether differences related to treatment existed between African American and white men who were diagnosed with prostate carcinoma during the period 1994-1995. METHODS: Cases were selected from 16 institutions within a region comprising 63 contiguous counties where the overall population was >20% African American. A stratified design was employed to accrue subjects into groups of even size according to race and disease stage (n = 231). A telephone survey was conducted, which assessed treatment options discussed by patients with their physicians, treatment(s) received, factors influencing treatment, satisfaction with treatments discussed and options given, and sociodemographic information. RESULTS: All measures related to treatment were consistently associated with stage at diagnosis (P < 0.001) rather than other variables measured (i.e., race, age, income, comorbidity, education, and residential status). Furthermore, most subjects reported that their physicians presented several treatment options (65%), that they were satisfied with the options presented (90%), and that the physician was the most important factor influencing their treatment decision (57%). CONCLUSIONS: These data suggest that African American and white men in North Carolina receive comparable treatment for prostate carcinoma. Therefore, efforts to reduce the racial disparity in mortality should be directed toward lessening the high incidence of later stage disease at diagnosis and exploring potential biologic differences that may increase the risk of more aggressive disease among African Americans.

Nutritional supplementation during the preschool years and physical work capacity in adolescent and young adult Guatemalans.

A follow-up study (1988-89) was carried out in 364 rural Guatemalans, 11-27 y of age, who earlier had participated in a nutritional supplementation experiment. Among its objectives was the assessment of the long-term effects of the nutrition intervention on physical work capacity. Subjects and their mothers from two villages had available a high-energy, high-protein supplement (Atole: 163 kcal/682 kJ and 6.4 g protein per serving or 180 mL), whereas in two other villages a low-energy, no-protein supplement (Fresco: 59 kcal/247 kJ per 180 mL) was provided. Consumption was ad libitum. Maximum oxygen consumption (VO2max) at follow-up was significantly greater in Atole compared with Fresco subjects of both sexes. In subjects 14-19 y, exposed to supplementation throughout gestation and the first 3 y of life, Atole males had a significantly higher VO2max (2.62 L/min) than Fresco males (2.24 L/min), the differences remaining significant even after controlling for body weight and fat-free mass; also, there was a significant positive relationship between amount of supplement consumed and VO2max. The supplementation effect in females of similar age was not statistically significant. It is concluded that early nutritional improvements can have long-lasting effects on physical performance.

The status of local smoking regulations in North Carolina following a state preemption bill.

OBJECTIVE: To determine the number and protectiveness of local smoking regulations adopted before the implementation of a preemptive statewide smoking control bill. METHOD: Review of local smoking control regulations from all 100 counties and 85 municipalities with populations greater than 5000 in North Carolina. MAIN OUTCOME MEASURES: Adoption of local smoking control regulations before and during the 3-month delay in enactment of the preemptive bill. Protectiveness of regulations was based on restrictions on smoking and requirements for separate ventilation systems at private work sites: none (smoking unrestricted); minimal (smoking restricted to designated areas); partial (smoking restricted to designated areas served by separate ventilation systems); and complete (smoking prohibited). Because some regulations would be phased in gradually over the next 5 years, we evaluated the requirements that will be in effect by January 1, 2000. RESULTS: Between July 15 and October 15, 1993, the number of local smoking regulations in North Carolina increased from 16 to 105. By the year 2000, 59% of private employees still will not be guaranteed any protection from work site environmental tobacco smoke; 19% will have minimal protection, 22% will have partial protection, and none will have complete protection. CONCLUSIONS: The 3-month delay in preemption created an unnatural time frame for communities to organize, debate, and adopt smoking restrictions. Despite the adoption of 89 new regulations, no private employees will be guaranteed complete protection from work site environmental tobacco smoke by the year 2000; new regulations can no longer be adopted. HB 957 has been a setback for public health in North Carolina.

Predicting body composition from anthropometry and bioimpedance in marginally undernourished adolescents and young adults.

Body-composition prediction equations were developed using data from a sample of 201 female and male Guatemalan ladinos (ie, people of Amerindian-European descent) aged 11-25 y. Fat-free mass (FFM) values were estimated from body density by using the two-component model and age- and sex-specific values for the density of FFM. The root-mean-square error (RMSE) of the best model predicting FFM from a set of simple anthropometric variables was 1.59 kg for females and 1.90 kg for males. The addition of more extensive anthropometry to the set of candidate predictors reduced the RMSE to 1.42 kg for females and 1.88 kg for males. The subsequent addition of a bioelectrical impedance measure (Ht2/R) further reduced the RMSE to 1.32 kg for females and 1.82 kg for males. These results suggest that for a marginally undernourished population with relatively little body fat, simple anthropometrics are as useful as more sophisticated measures for the prediction of body composition.