Development and evaluation of the physical activity questionnaire for elderly Japanese: the Nakanojo study

The Physical Activity Questionnaire for Elderly Japanese (PAQ-EJ) is a self-administered physical activity questionnaire for elderly Japanese; the authors report here on its repeatability and direct and indirect validity. Reliability was assessed by repeat administration after 1 month. Direct validation was based on accelerometer data collected every 4 s for 1 month in 147 individuals age 65-85 years. Indirect validation against a 10-item Barthel index (activities of daily living [ADL]) was completed in 3,084 individuals age 65-99 years. The test-retest coefficient was high (r = .64-.71). Total and subtotal scores for lower (transportation, housework, and labor) and higher intensity activities (exercise/sports) were significantly correlated with step counts and durations of physical activity <3 and >or=3 METs (r = .41, .28, .53), respectively. Controlling for age and ADL, scores for transportation, exercise/sports, and labor were greater in men, but women performed more housework. Sex- and ADL- or age-adjusted PAQ-EJ scores were significantly lower in older and dependent people. PAQ-EJ repeatability and validity seem comparable to those of instruments used in Western epidemiological studies.     

A Bayesian Learning Coefficient of Generalization Error and Vandermonde Matrix-Type Singularities

The coefficient of the main term of the generalization error in Bayesian estimation is called a Bayesian learning coefficient. In this article, we first introduce Vandermonde matrix type singularities and show certain orthogonality conditions of them. Recently, it has been recognized that Vandermonde matrix type singularities are related to Bayesian learning coefficients for several hierarchical learning models. By applying the orthogonality conditions of them, we show that their log canonical threshold also corresponds to the Bayesian learning coefficient for normal mixture models, and we obtain the explicit computational results in dimension one.     

Population-level analysis on reduction in equilibrium population size of the azuki bean beetle

Summary Responses of laboratory population of the azuki bean beetleCallosobruchus chinensis to temperature conditions of 30°C and 32°C are compared. Equilibrium population size was found to be lower at 32°C. A one-generation process examined by reproduction-curve experiments is divided into two consecutive life stages specified by different habitats, i.e., outside and inside beans. Modified logistic difference equations are used to describe these population-level responses at each life stages. Sensitivity analysis is used to determine parameters of importance, thus determining the main cause of the reduced equilibrium population size at 32°C. The reduction resulted from the decrease in maximum population size of emerged adults which have experienced inside-bean process. The application and limitation of this population-level analysis to different levels are discussed.     

What motivates single women to save? the case of Japan

Using Japanese panel data, we analyze precautionary savings due to staying single in the presence of income uncertainty. Our panel analysis finds that compared with young women who are likely to get married within 3 years, those who are not plan to have 44 percent more savings for precautionary purposes, and 108 percent more for retirement. These results suggest that in facing higher risk of income fluctuation due to choosing to marry late or remain unmarried, young women intend to have more wealth to mitigate the income risk inherent in single life.     

Yearlong physical activity and health-related quality of life in older Japanese adults: the Nakanojo Study

We hypothesized that the health-related quality of life (HRQOL) would be poorer in physically inactive older adults. This was tested in a sample of 73 male and 108 female free-living healthy Japanese participants, age 65-85 years. We measured accelerometer step counts and their metabolic equivalents (METs) throughout each 24-hr period for 1 year. At the end of the year, HRQOL was assessed. Physical activity was grouped into quartiles. HRQOL was poorer in the lowest quartiles of participants with respect to both step count and duration of activity >3 METs; however, our sample showed no better HRQOL in those participants exceeding minimum standards of daily physical activity, corresponding to counts of around 5,500 and 4,500 steps/day and durations of around 13 and 14 min/day in men and women, respectively. Causation cannot be demonstrated from this cross-sectional study, but nevertheless we suggest that elderly individuals should be encouraged to meet such standards of habitual physical activity.     

Sex, age, season, and habitual physical activity of older Japanese: the Nakanojo study

The interactions of sex, age, season, and habitual physical activity were examined in 41 male and 54 female Japanese age 65-83 yr, using a pedometer/accelerometer that determined step counts and amounts of physical activity (<3 and >3 metabolic equivalents [METs]) throughout each 24-hr period for an entire year. All 3 measures were greater in men than in women. In women, age was negatively correlated with step count and activity <3 METs, but in men, it was correlated with step count and activity >3 METs. Irrespective of sex or age, all 3 activity variables were low in the winter, peaking in spring or autumn. In the summer, step counts matched the annual average, but durations of activity <3 and >3 METs were, respectively, longer and shorter than in other seasons. These findings have practical implications for those promoting physical activity for older adults.     

Evolutionary character changes and population responses in an insect host-parasitoid experimental system

In an insect host (the cowpea weevilCallosobruchus maculatus)- parasitoidHeterospilus prosopidis) experimental system, the population densities of the component species oscillated for the first 20 generations and then abruptly stabilized as the parasitoid density decreased. Examination of the host and parasitoid after the 40th generation in the long-term experiment showed that (1) host larvae exhibited contest-type competition (killing other larvae inhabiting the same bean), in contrast to the founder population being scramble-type competitors and (2) the parasitoid attack rate on the host did not change. There was also an evolutionary trade-off between body size and the rates of larval survival and development, suggesting a cost of contest competition on larval survivorship and development. I tested model predictions (Tuda and Iwasa 1998) that (1) host equilibrium population size should gradually decrease as the proportion of the contest type increases and that (2) random attacks of the parasitoid on the host should reduce the rate of increase in proportion of the contest type, and the effect should become manifest especially during the first 20 generations. Two of three host-only replicates showed significant decrease in population sizes. Although the density of emerging adults per bean did not differ between replicates of the host-only and host-parasitoid systems, comparison of the host body size between them on day 270 (at the 13th generation) showed that the host was more contest-type in the host-only system than in the host-parasitoid system, as the model predicted, and later on day 650 the effect of the parasitoid had disappeared.     

Temporal/spatial structure and the dynamical property of laboratory host-parasitoid systems

The effects of spatial structure in terms of local capacity, or the maximum number of larvae surviving competition at resource patches, and temporal structure in terms of the period vulnerable to parasitoid attack in host populations on the persistence of host-parasitoid systems were quantitatively evaluated by laboratory experiments and well-parameterized model analyses. One of two bruchid beetles,Callosobruchus maculatus andC. phaseoli, were used as a host with Heterospilus prosopidis used as the parasitoid.C. maculatus, in which few larvae survive competition to become adults in each bean, andC. phaseoli, in which many larvae become adults in each bean, along with two kinds of beans, the mung and the azuki, were combined to construct four (2×2) resource-herbivorous host-parasitoid systems that differed in local capacity and vulnerable period. The mung-C. maculatus system with the parasitoid was the most persistent, i.e., took the longest time for extinction of either the host or parasitoid to occur. Since this resource-herbivorous host combination exhibited the lowest local capacity and the shortest vulnerable period, these two conditions possibly promoted the persistence of the system. A model incorporating the host population structure supported the observed persistence. Furthermore, the possible contribution of the timing of density-dependent competition of the host on the host-parasitoid persistence is predicted.     

Abating Stereotypical Attitudes: Views on Career Paths of an Asian American Comedian

An Asian American comedian, William Mar, provides an insightful commentary about his career choice. He believes that the comedy stage is a useful position to comment on stereotypes inherent to the American culture. Comedians must challenge the audience to think about the joke not only as amusement, but to examine the other implications involved.     

Density dependence depends on scale; at larval resource patch and at whole population

Summary A previous study (Tuda and Shimada, 1993) has shown that the equilibrium population size of the azuki bean beetle was lower at 32°C than at 30°C and that this difference was due to a reduced maximum population size of emerged progeny through inside-bean process. In this paper, these results were analyzed further on the scale of the individual bean where interaction among larvae took place. Per-bean numbers of deposited eggs, hatched eggs, and emerged adults have been recorded at seven different parental densities under the two temperature conditions. Three individual-bean-scale process hypotheses that may explain the reduced maximum emergence density on the whole population scale are suggested: (1) a lower maximum emergence per bean at 32°C than at 30°C, if the bean scale and the wholepopulation scale share the same density-dependent pattern in adult emergence, (2) a limited range of hatched egg number per bean at 32°C, resulting from the adult oviposition process outside beans, and (3) different patterns of density-dependent emergence between the two different scales. This study showed that the inside-bean pattern of responses on the bean scale was a simple saturated curve at 30°C, but one with a discontinuous decline at higher hatched egg densities at 32°C. On the contrary, during outside-bean process, the peak number of hatched eggs decreased on this scale as observed on the wholepopulation scale. I discuss why the extracted factor of inside-bean process on the whole-population in the previous study could not be applied to the bean-scale pattern.