Int J Geriatr Psychiatry

Objectives Hearing, vision, and cognitive impairment commonly co‐occur in older adults. Improving sensory function may positively impact outcomes in people with dementia (PwD). We developed a “sensory intervention” (SI) to support hearing and vision in PwD. Here, we report the findings of an international open‐label field trial, and nested case series, to explore the impact of the SI on dementia‐related outcomes. Methods This was a home‐based trial conducted in France, England, and Cyprus. Participants were people with mild‐to‐moderate dementia and hearing and/or vision impairment (n = 19) and their study partners (unpaid carers; n = 19). The “basic” SI included a hearing and vision assessment and provision of glasses and/or hearing aids. A subsample received the “extended” SI with additional weekly visits from a sensory support therapist (SST). Exploratory analyses of dementia‐related, health utility and resource utilisation outcomes were performed. Results Quality of life (QoL) and sensory functional ability improved. Change in QoL exceeded the threshold for a minimum clinically important difference. There was a modest improvement (in absolute terms) post intervention in behavioural disturbance, self‐efficacy, and relationship satisfaction. Study partner time assisting instrumental activities of daily living (iADL) and supervision decreased by about 22 and 38 hours per month, respectively, although time for personal ADL support increased. Qualitative data supported effectiveness of the intervention: PwD were more socially engaged, less isolated, less dependent on study partners, and had improved functional ability and communication. Conclusions These findings support the need for a definitive randomised controlled trial (RCT) to evaluate the effectiveness of the intervention

Diabetes and dementia risk

Le diabète de type 2 est un facteur de risque de démence mais aucun bénéfice d’un contrôle intensif de l’hyperglycémie n’a été démontré jusqu’à présent. Nous avons exploré plusieurs explications potentielles à ces résultats. Tout d’abord, le diabète étant une cause importante de mortalité, nous avons estimé le risque de démence associé au diabète en tenant compte du risque compétitif de décès, dans une cohorte en population générale âgée française. Le diabète était associé à un risque plus élevé de démence et à une réduction de 2 à 3 ans de l’espérance de vie sans démence, sans qu’aucune caractéristique modificatrice de l’effet du diabète ne soit identifiée. Ces résultats confirment l’intérêt de la prévention et du traitement du diabète pour la réduction du risque de démence, pour l’ensemble des personnes âgées diabétiques. Nous avons ensuite estimé le rôle de médiation joué par différentes modifications cérébrales dans l’association entre diabète et statut cognitif. D’une part, nous avons montré que l’effet délétère du diabète sur le risque de démence était significativement médié par un effet distinct sur l’atrophie cérébrale et les lésions cérébrovasculaires, en population générale âgée. D’autre part, nous avons montré que l’effet délétère du diabète sur les performances cognitives était significativement médié par une neurodégénérescence plus élevée, indépendamment des lésions cérébrovasculaires et des biomarqueurs de la maladie d’Alzheimer. Ces résultats concordants suggèrent l’importance de l’effet direct du diabète sur la neurodégénérescence. Les perturbations métaboliques liées au diabète pouvant expliquer cette association doivent être explorées.Type 2 diabetes is a risk factor for dementia, but no benefit of intensive glycaemic control has been identified so far. We explored several potential reasons for those conflicting findings. First, as diabetes is a major cause of mortality, we estimated the diabetes-associated risk of dementia considering the competing risk of death, in a population-based cohort of French older adults. Diabetes was associated with a higher dementia risk and a 2-to-3-year lower dementia-free life expectancy; no effect modification was shown. These results confirm the potential impact of diabetes prevention and treatment in reducing dementia risk. Second, we estimated the mediating effect of several brain biomarkers in the association of diabetes with cognitive status. We found that (1) brain atrophy and cerebrovascular lesions had a significant and independent mediating effect in the diabetes-dementia association in community-dwelling older adults, and (2) the association of diabetes with lower cognition was significantly mediated by higher neurodegeneration, independently of cerebrovascular lesions and Alzheimer’s disease biomarkers. These consistent results suggest the importance of the direct effect of diabetes on neurodegeneration. Diabetes-associated metabolic alterations that may explain this association should be explored

Diabète et risque de démence

Type 2 diabetes is a risk factor for dementia, but no benefit of intensive glycaemic control has been identified so far. We explored several potential reasons for those conflicting findings. First, as diabetes is a major cause of mortality, we estimated the diabetes-associated risk of dementia considering the competing risk of death, in a population-based cohort of French older adults. Diabetes was associated with a higher dementia risk and a 2-to-3-year lower dementia-free life expectancy; no effect modification was shown. These results confirm the potential impact of diabetes prevention and treatment in reducing dementia risk. Second, we estimated the mediating effect of several brain biomarkers in the association of diabetes with cognitive status. We found that (1) brain atrophy and cerebrovascular lesions had a significant and independent mediating effect in the diabetes-dementia association in community-dwelling older adults, and (2) the association of diabetes with lower cognition was significantly mediated by higher neurodegeneration, independently of cerebrovascular lesions and Alzheimer’s disease biomarkers. These consistent results suggest the importance of the direct effect of diabetes on neurodegeneration. Diabetes-associated metabolic alterations that may explain this association should be explored.Le diabète de type 2 est un facteur de risque de démence mais aucun bénéfice d’un contrôle intensif de l’hyperglycémie n’a été démontré jusqu’à présent. Nous avons exploré plusieurs explications potentielles à ces résultats. Tout d’abord, le diabète étant une cause importante de mortalité, nous avons estimé le risque de démence associé au diabète en tenant compte du risque compétitif de décès, dans une cohorte en population générale âgée française. Le diabète était associé à un risque plus élevé de démence et à une réduction de 2 à 3 ans de l’espérance de vie sans démence, sans qu’aucune caractéristique modificatrice de l’effet du diabète ne soit identifiée. Ces résultats confirment l’intérêt de la prévention et du traitement du diabète pour la réduction du risque de démence, pour l’ensemble des personnes âgées diabétiques. Nous avons ensuite estimé le rôle de médiation joué par différentes modifications cérébrales dans l’association entre diabète et statut cognitif. D’une part, nous avons montré que l’effet délétère du diabète sur le risque de démence était significativement médié par un effet distinct sur l’atrophie cérébrale et les lésions cérébrovasculaires, en population générale âgée. D’autre part, nous avons montré que l’effet délétère du diabète sur les performances cognitives était significativement médié par une neurodégénérescence plus élevée, indépendamment des lésions cérébrovasculaires et des biomarqueurs de la maladie d’Alzheimer. Ces résultats concordants suggèrent l’importance de l’effet direct du diabète sur la neurodégénérescence. Les perturbations métaboliques liées au diabète pouvant expliquer cette association doivent être explorées

Using satellite scatterometers to monitor continental surfaces

International audienc

Characterization of west African land surface state autumn to summer evolution regarding Sahelian rainfall variability.

Avril 2005The ERS backscattering coefficient (0) and CMAP rainfall datasets are analyzed over period 1992-2000 to document the autumn to summer soil-vegetation water content evolution in West Africa regarding Sahelian rainfall variability. A composite analysis performed over 0 field averaged between longitudes 10°W- 10°E shows that the wettest (driest) July-September Sahelian rainy seasons have been preceded by negative (positive) anomalies of soil-vegetation water content over the Sudanian belt in June and positive (negative) ones over Guinea from winter to spring. While the former anomalies are linked to synchronous rainfall deficits, sign of delayed northward jump of the ITCZ, the latter do not coincide with any synchronous signal in precipitations. A 'Granger causality' analysis reveals that spring (March- May) anomalies of soil-vegetation water content are rather due to those recorded in rainfall during the preceding autumn (September-November) than to a persistence of winter 0 anomalies. These findings argue for inter-season memory effects in West Africa held by land surface state. Lastly, the positive anomalies of soil-vegetation water content from winter to spring over the Guinea belt induce a steeper (a flatter) meridional gradient over the subcontinent: it has been shown that the meridional arrangement of biosphere and soil water content over West Africa is critical for monsoon dynamics

Characterization of west African land surface state autumn to summer evolution regarding Sahelian rainfall variability.

Avril 2005The ERS backscattering coefficient (0) and CMAP rainfall datasets are analyzed over period 1992-2000 to document the autumn to summer soil-vegetation water content evolution in West Africa regarding Sahelian rainfall variability. A composite analysis performed over 0 field averaged between longitudes 10°W- 10°E shows that the wettest (driest) July-September Sahelian rainy seasons have been preceded by negative (positive) anomalies of soil-vegetation water content over the Sudanian belt in June and positive (negative) ones over Guinea from winter to spring. While the former anomalies are linked to synchronous rainfall deficits, sign of delayed northward jump of the ITCZ, the latter do not coincide with any synchronous signal in precipitations. A 'Granger causality' analysis reveals that spring (March- May) anomalies of soil-vegetation water content are rather due to those recorded in rainfall during the preceding autumn (September-November) than to a persistence of winter 0 anomalies. These findings argue for inter-season memory effects in West Africa held by land surface state. Lastly, the positive anomalies of soil-vegetation water content from winter to spring over the Guinea belt induce a steeper (a flatter) meridional gradient over the subcontinent: it has been shown that the meridional arrangement of biosphere and soil water content over West Africa is critical for monsoon dynamics

Analysis of the linkages between rainfall and land surface conditions in the West African monsoon through CMAP, ERS-WSC, and NOAA-AVHRR data

International audienceThe European Remote Sensing Wind Scatterometer (ERS-WSC) backscattering coefficient, NOAA Advanced Very High Resolution Radiometer (NOAA-AVHRR) Normalized Difference Vegetation Index (NDVI), and Climate Prediction Center Merged Analysis Precipitation ( CMAP) precipitation data sets are studied over the period August 1991 to December 2000 to document ( 1) the interannual and intra-annual evolutions of vegetation photosynthetic activity and soil-vegetation water content over West Africa and ( 2) their two-way links with precipitation. Over the Sahel, at interannual timescales the strongest relationships between vegetation, soil moisture, and precipitation are observed from July to October and when 1-month lag is considered between the parameters. This delay reflects the vegetation response time to the moisture pulses that follow precipitation events. The high correlation between NDVI and sigma_0 at interannual timescales confirms the importance of vegetation in the backscattering coefficient. However, sigma_0 shows stronger statistical links with precipitation, suggesting that this product contains additional useful information related in particular to upper soil moisture. Over Guinea, large differences are observed between the two remote sensing products, and their relationship with precipitation at interannual timescales is weaker. Sigma_ 0 is significantly linked to precipitation from July to November, whereas NDVI does not show any significant relationship with precipitation. NDVI and sigma_0 serial correlations over the Sahel and Guinea suggest that a 2-month memory usually characterizes vegetation photosynthetic activity and soil-vegetation water content anomalies. However, anomalies disappearance in winter then reappearance in the following spring also suggests an interseason memory held by deep soil moisture reservoirs and deep-rooted plants. A composite analysis reveals that the wettest Sahelian rainy seasons were preceded by positive anomalies of soil-vegetation water content over Guinea from winter to spring. Cross correlations and Granger causality analyses partly relate these winter to spring land surface anomalies to those recorded in precipitation during the previous autumn. Spring soil-vegetation water content anomalies strengthen the meridional gradient of soil-vegetation water content over the subcontinent. This gradient is thought to contribute to the gradient of entropy that drives the West African monsoon

Comparison of ERS wind-scatterometer and SSM/I data for sahelian vegetation monitoring

International audienceERS wind scatterometer (WSC) and SSM/I data are compared for monitoring the seasonal variation of herbaceous vegetation over a sahelian region. Temporal evolution of polarization difference brightness temperatures derived from SSM/I data and WSC backscattering coefficient acquired at 45 degrees of incidence angle over four different sites during the period 1992-1993, exhibits a marked seasonality with opposite and symmetrical trends, Observed differences between both signals are mainly attributed to atmospheric effects affecting SSM/I data. The use of a semi-empirical model during the 1992 rainy season shows that Delta T temporal evolution is mainly due to the variation of integrated water vapor content of the atmosphere, surface, and air temperature, soil moisture content, and bare soil fraction area. In order to retrieve biomass from SSM/I data, an inversion procedure is performed and compared to previous results obtained with ERS WSC data. The absence of accurate atmospheric data over the Sahel, combined with the sensitivity of the passive model to soil moisture leads to poor results with regard to biomass retrieval from SSM/I data

Land surface parameter monitoring with ERS scatterometer data over the Sahel: A comparison between agro-pastoral and pastoral areas

International audienceThis paper deals with ERS wind scatterometer (WSC) data for land surface monitoring over the Sahel on a regional scale. Past studies have shown that WSC is particularly well suited for monitoring Sahelian pastoral regions consisting of large homogeneous herbaceous steppes (Jarlan et al., 2002a and Jarlan et al., 2002b). On the other hand, Sahelian agro-pastoral areas are more heterogeneous in terms of WSC spatial cell resolution owing to different land use caused by anthropic pressure. The objective of this paper is to assess the suitability of WSC data in such a heterogeneous landscape. To this end, WSC data for an agro-pastoral area are compared with results presented in Jarlan et al., 2002b which focused on 4 pastoral sites, located in Mali. The agro-pastoral area concerned is in the Fakara region (Niger), for which numerous in situ measurements are available for the 1994–2000 period over a 500 km2 area. WSC temporal signatures acquired at a 45° incidence angle, σ0(45°), show the typical behaviour observed over the Sahelian areas. σ0(45°) values are higher than those observed by Jarlan et al. (2002b) over Northern Sahelian sites, especially during the dry season, and exhibit a lower yearly amplitude variability. The effect of land use heterogeneity on the radar signal is investigated by comparing WSC profiles acquired at a 21° incidence angle, σ0(21°), with ERS SAR data during the year 1995. The observations are interpreted by combining a radiative transfer model and a vegetation growth model in a similar approach to the one developed by Frison et al., 1998 and Jarlan et al., 2002a, Jarlan et al., 2002b and Jarlan et al., 2003. The results indicate that at an incidence angle of 21°, soil contribution is largely predominant, representing 90% of the radar signal, thus explaining the similar behaviour of radar signatures observed despite different land uses. At a 45° incidence angle, even though annual vegetation and bare soil are the two main factors influencing the temporal evolution of the radar signal, the bare soil contribution is still the most significant. It is shown that over the present study site, characterised by low annual vegetation fraction cover and high σ0(45°) values during the dry season, vegetation makes no significant contribution to the yearly amplitude of the radar signal, σadr0(45°). The latter can be explained by the bare soil contribution alone. Consequently, limited soil moisture due to small field capacity accounts for the small σadr0(45°) variability observed. An inversion method to retrieve the volumetric soil moisture content, Hv, using σ0(45°) data is then developed. It appears that vegetation has a negligible influence over estimated Hv. As a result, the soil moisture content can be retrieved from WSC data alone, by representing the present scene as being composed of bare soil only. These results differ from those obtained over pastoral Sahelian sites, where both vegetation and soil moisture play significant roles in radar response. Moreover, the comparison between WSC σ0(45°) retrieved soil moisture with existing soil moisture derived from passive microwave radiometer SSM/I measurements shows a fairly good overall match

Analysis of L and C-bands SAR images time series over a Sahelian area

International audienceThis paper presents an analysis of two Synthetic Aperture Radar (SAR) images time-series over a Sahelian area, located in the Gourma region, Mali. The first one is acquired at C band by the ENVISAT - Advanced SAR (ASAR) sensor in Wide-Swath (WS) mode, and the second one at L band by the ALOS - Phased Array type L-band SAR (PALSAR) in Fine, Dual, and WS modes. A change detection method based on random projection and the Hue-Saturation-Value (HSV) transform appears to be very well appropriated to detect the temporal changes appearing on both data sets. The results illustrate the higher penetration depth of L band over such sandy soils. The C band time series is found to be very sensitive to surface changes (soil moisture and vegetation growth). By contrast, the L band time series appear to be very stable over the sandy soils, the only temporal changes occurring over temporary or permanent ponds