Health Status transitions in community-living elderly with complex care needs: a latent class approach.

ckground: For older persons with complex care needs, accounting for the variability and interdependency in how health dimensions manifest themselves is necessary to understand the dynamic of health status. Our objective is to test the hypothesis that a latent classification can capture this heterogeneity in a population of frail elderly persons living in the community. Based on a person-centered approach, the classification corresponds to substantively meaningful groups of individuals who present with a comparable constellation of health problems. Methods: Using data collected for the SIPA project, a system of integrated care for frail older people (n = 1164), we performed latent class analyses to identify homogenous categories of health status (i.e. health profiles) based on 17 indicators of prevalent health problems (chronic conditions; depression; cognition; functional and sensory limitations; instrumental, mobility and personal care disability) Then, we conducted latent transition analyses to study change in profile membership over 2 consecutive periods of 12 and 10 months, respectively. We modeled competing risks for mortality and lost to follow-up as absorbing states to avoid attrition biases. Results: We identified four health profiles that distinguish the physical and cognitive dimensions of health and capture severity along the disability dimension. The profiles are stable over time and robust to mortality and lost to follow-up attrition. The differentiated and gender-specific patterns of transition probabilities demonstrate the profiles' sensitivity to change in health status and unmasked the differential relationship of physical and cognitive domains with progression in disability. Conclusion: Our approach may prove useful at organization and policy levels where many issues call for classification of individuals into pragmatically meaningful groups. In dealing with attrition biases, our analytical strategy could provide critical information for the planning of longitudinal studies of aging. Combined, these findings address a central challenge in geriatrics by making the multidimensional and dynamic nature of health computationally tractable.This research was funded through a PhD dissertation grant supplied to the first author by the Quebec Network for Research on Aging

DNA adducts, cell proliferation and papilloma latency time in mouse skin after repeated dermal application of DMBA and TPA

The mouse skin tumor model was used to investigate whether the level of DNA adducts and/or the rate of cell division in the epidermis are indicators of the risk of cancer formation for an individual in an outbred animal population. A high risk was considered to be reflected by a short latency period for the appearance of a papilloma. Female NMRI mice were treated twice weekly with 2.5 nmol 7,12-dimethylbenz[a]anthracene (DMBA) and 3 nmol 12-O-tetradecanoylphorbol-13-acetate (TPA) and the appearance of papillomas was registered. The first papilloma appeared after 7.5 weeks. After 17 weeks, when 12 of 14 mice had at least one papilloma, an osmotic minipump delivering 5-bromo-2'-deoxyuridine (BrdU) was implanted into each mouse for 24 h. The mice were killed after 24 h and the epidermis was analyzed for DMBA-nucleotide adducts by 32P-postlabeling, for the cell number per unit skin length, and for the labeling index for DNA synthesis. Unexpectedly, DMBA-nucleotide adduct levels were highest in those animals which showed the longest latency periods. Adduct levels were negatively correlated with the labeling index, indicating that dilution of adducts by cell division was a predominant factor in determining average adduct concentrations. Individual tumor-latency time was not correlated with either cell number or labeling index. This could be due to the fact that the measurements only provided averaged data and gave no information on the specific situation in clones of premalignant cells. Under the conditions of this assay, therefore, neither DNA adduct levels nor information on the average kinetics of cell division had a predictive value for the individual cancer risk within a group of outbred animals receiving the same treatmen

Polarization of Broad Absorption Line QSOs I. A Spectropolarimetric Atlas

We present a spectropolarimetric survey of 36 broad absorption line quasi-stellar objects (BAL QSOs). The continuum, absorption trough, and emission line polarization of BAL QSOs yield clues about their structure. We confirm that BAL QSOs are in general more highly polarized than non-BAL QSOs, consistent with a more equatorial viewing direction for the former than the latter. We have identified two new highly-polarized QSOs in our sample (1232+1325 and 1333+2840). The polarization rises weakly to the blue in most objects, perhaps due to scattering and absorption by dust particles. We find that a polarization increase in the BAL troughs is a general property of polarized BAL QSOs, indicating an excess of scattered light relative to direct light, and consistent with the unification of BAL QSOs and non-BAL QSOs. We have also discovered evidence of resonantly scattered photons in the red wing of the C IV broad emission lines of a few objects. In most cases, the broad emission lines have lower polarization and a different position angle than the continuum. The polarization characteristics of low-ionization BAL QSOs are similar to those of high-ionization BAL QSOs, suggesting a similar BAL wind geometry.Comment: 39 pages, 6 figures (20 .gif files), accepted for publication in The Astrophysical Journal Supplement

Time-resolved optical spectroscopy of the pulsating DA white dwarf HS 0507+0434B: New constraints on mode identification and pulsation properties

We present a detailed analysis of time-resolved optical spectra of the ZZ Ceti white dwarf, HS 0507+0434B. Using the wavelength dependence of observed mode amplitudes, we deduce the spherical degree, l, of the modes, most of which have l=1. The presence of a large number of combination frequencies (linear sums or differences of the real modes) enabled us not only to test theoretical predictions but also to indirectly infer spherical and azimuthal degrees of real modes that had no observed splittings. In addition to the above, we measure line-of-sight velocities from our spectra. We find only marginal evidence for periodic modulation associated with the pulsation modes: at the frequency of the strongest mode in the lightcurve, we measure an amplitude of 2.6+/-1.0 km/s, which has a probability of 2% of being due to chance; for the other modes, we find lower values. Our velocity amplitudes and upper limits are smaller by a factor of two compared to the amplitudes found in ZZ Psc. We find that this is consistent with expectations based on the position of HS 0507+0434B in the instability strip. Combining all the available information from data such as ours is a first step towards constraining atmospheric properties in a convectionally unstable environment from an observational perspective.Comment: 16 pages, 12 figs.; accepted for publication in A&

The masses of the millisecond pulsar J1012+5307 and its white-dwarf companion

We report on spectroscopy of the white-dwarf companion of the millisecond radio pulsar PSR J1012+5307. We find strong Balmer absorption lines, as would be expected for a cool DA white dwarf. The profiles are much narrower than usual, however, and lines are seen up to H12, indicating that the companion has a low gravity and hence a low mass. This is consistent with the expectation---based on evolutionary considerations and on the mass function---that it is a low-mass white dwarf with a helium core. By comparing the spectra to model atmospheres, we derive an effective temperature $T_{\rm{}eff}=8550\pm25\,$K and a surface gravity $\log{}g=6.75\pm0.07$ (cgs units). Using the Hamada-Salpeter mass-radius relation for helium white dwarfs, with an approximate correction for finite-temperature effects, we infer a mass \mwd=0.16\pm0.02\,\msun. This is the lowest mass among all spectroscopically identified white dwarfs. We determine radial velocities from our spectra, and find a radial-velocity amplitude of 280\pm15\,\kms. With the pulsar's radial-velocity amplitude, the mass ratio \mpsr/\mwd=13.3\pm0.7. From all constraints, we find that with 95\% confidence 1.5<\mpsr/\msun<3.2.Comment: 6 pages of text and figures. Refereed version, resubmitted to ApJL. Needs aas2pp4.sty, epsf.st