Differences in the progression of disability: a U.S.-Mexico comparison

Objectives: This article seeks to document the progression of disability in a developing country by implementing a model to examine how this process compares to a developed country. Methods: Data come from the Mexican Health and Aging Study (MHAS), including a baseline survey in 2001 and a follow-up in 2003, and from the U.S. Health and Retirement Study (HRS), using the 2000 and 2002 waves. An ordinal logistic regression approach is used to examine a progression of disability that considers (a) no disability, (b) mobility problems, (c) mobility plus limitations with instrumental activities of daily living, (d) mobility plus limitations with activities of daily living (ADLs), (e) limitations in all three areas and (f) death. Results: In both data sets, approximately 44% of the sample remained in the same level of disability at the 2-year follow-up. However, the progression of limitations with two disabilities differs by gender in the MHAS but is consistent for both men and women in the HRS. Discussion: Our model reflects the importance of ADLs in the disablement process in Mexico. We speculate that the difference in lifetime risk profiles and cultural context might be responsible for the divergence in the progression of disability by gender. Keywords: Gender differences; HRS, Mexico; MHAS; Progression of disability; USA</p

Cross-national health comparisons using the Rasch model: findings from the 2012 US Health and Retirement Study and the 2012 Mexican Health and Aging Study

Purpose Cross-national comparisons of patterns of population aging have emerged as comparable national micro-data have become available. This study creates a metric using Rasch analysis and determines the health of American and Mexican older adult populations. Methods Secondary data analysis using representative samples aged 50 and older from 2012 U.S. Health and Retirement Study (n&thinsp;=&thinsp;20,554); 2012 Mexican Health and Aging Study (n&thinsp;=&thinsp;14,448). We developed a function measurement scale using Rasch analysis of 22 daily tasks and physical function questions. We tested psychometrics of the scale including factor analysis, fit statistics, internal consistency, and item difficulty. We investigated differences in function using multiple linear regression controlling for demographics. Lastly, we conducted subgroup analyses for chronic conditions. Results The created common metric demonstrated a unidimensional structure with good item fit, an acceptable precision (person reliability&thinsp;=&thinsp;0.78), and an item difficulty hierarchy. The American adults appeared less functional than adults in Mexico (&beta;&nbsp;=&thinsp;&minus;&thinsp;0.26, p&thinsp;&lt;&thinsp;0.0001) and across two chronic conditions (arthritis, &beta;&nbsp;=&thinsp;&minus;&thinsp;0.36; lung problems, &beta;&nbsp;=&thinsp;&minus;&thinsp;0.62; all p&thinsp;&lt;&thinsp;0.05). However, American adults with stroke were more functional than Mexican adults (&beta;&nbsp;=&thinsp;0.46, p&thinsp;=&thinsp;0.047). Conclusions The Rasch model indicates that Mexican adults were more functional than Americans at the population level and across two chronic conditions (arthritis and lung problems). Future studies would need to elucidate other factors affecting the function differences between the two countries.</p

Disability Measurement for Korean Community-Dwelling Adults With Stroke: Item-Level Psychometric Analysis of the Korean Longitudinal Study of Ageing

Objective: To investigate the psychometric properties of the activities of daily living (ADL) instrument used in the analysis ofKorean Longitudinal Study of Ageing (KLoSA) dataset.Methods: A retrospective study was carried out involving 2006 KLoSA records of community-dwelling adults diagnosed withstroke. The ADL instrument used for the analysis of KLoSA included 17 items, which were analyzed using Rasch modelingto develop a robust outcome measure. The unidimensionality of the ADL instrument was examined based on confirmatoryfactor analysis with a one-factor model. Item-level psychometric analysis of the ADL instrument included fit statistics, internalconsistency, precision, and the item difficulty hierarchy.Results: The study sample included a total of 201 community-dwelling adults (1.5% of the Korean population with an age over 45years; mean age=70.0 years, SD=9.7) having a history of stroke. The ADL instrument demonstrated unidimensional construct. Twomisfit items, money management (mean square [MnSq]=1.56, standardized Z-statistics [ZSTD]=2.3) and phone use (MnSq=1.78,ZSTD=2.3) were removed from the analysis. The remaining 15 items demonstrated good item fit, high internal consistency (personreliability=0.91), and good precision (person strata=3.48). The instrument precisely estimated person measures within a widerange of theta (-4.75 logits &lt; q &lt; 3.97 logits) and a reliability of 0.9, with a conceptual hierarchy of item difficulty.Conclusion: The findings indicate that the 15 ADL items met Rasch expectations of unidimensionality and demonstrated goodpsychometric properties. It is proposed that the validated ADL instrument can be used as a primary outcome measure forassessing longitudinal disability trajectories in the Korean adult population and can be employed for comparative analysis ofinternational disability across national aging studies

Specialized proteomic responses and an ancient photoprotection mechanism sustain marine green algal growth during phosphate limitation

Marine algae perform approximately half of global carbon fixation, but their growth is often limited by the availability of phosphate or other nutrients 1,2 . As oceans warm, the area of phosphate-limited surface waters is predicted to increase, resulting in ocean desertification 3,4 . Understanding the responses of key eukaryotic phytoplankton to nutrient limitation is therefore critical 5,6 . We used advanced photo-bioreactors to investigate how the widespread marine green alga Micromonas commoda grows under transitions from replete nutrients to chronic phosphate limitation and subsequent relief, analysing photosystem changes and broad cellular responses using proteomics, transcriptomics and biophysical measurements. We find that physiological and protein expression responses previously attributed to stress are critical to supporting stable exponential growth when phosphate is limiting. Unexpectedly, the abundance of most proteins involved in light harvesting does not change, but an ancient light-harvesting-related protein, LHCSR, is induced and dissipates damaging excess absorbed light as heat throughout phosphate limitation. Concurrently, a suite of uncharacterized proteins with narrow phylogenetic distributions increase multifold. Notably, of the proteins that exhibit significant changes, 70 are not differentially expressed at the mRNA transcript level, highlighting the importance of post-transcriptional processes in microbial eukaryotes. Nevertheless, transcript-protein pairs with concordant changes were identified that will enable more robust interpretation of eukaryotic phytoplankton responses in the field from metatranscriptomic studies. Our results show that P-limited Micromonas responds quickly to a fresh pulse of phosphate by rapidly increasing replication, and that the protein network associated with this ability is composed of both conserved and phylogenetically recent proteome systems that promote dynamic phosphate homeostasis. That an ancient mechanism for mitigating light stress is central to sustaining growth during extended phosphate limitation highlights the possibility of interactive effects arising from combined stressors under ocean change, which could reduce the efficacy of algal strategies for optimizing marine photosynthesis. © 2018 The Author(s)