Diversity of some gene frequencies in European and Asian populations. III. Spatial correlogram analysis

Effectiveness of a digitally supported care management programme to reduce unmet needs of family caregivers of people with dementia: study protocol for a cluster randomised controlled trial (GAIN)

Background

Up to two-thirds of dementia care is provided by family caregivers who often experience high burden, little support and adverse health outcomes. Enabling and supporting family caregivers to provide care at home prevents early institutionalisation of the person with dementia and alleviates the economic burden of dementia in the long term. General practitioners (GPs), as the first point of contact, have a key role in identifying and managing burden and care needs of family caregivers. However, in routine care, this opportunity is often limited by time constraints and even if caregiver needs are recognised, detailed information about regionally available support and advice on healthcare services is often lacking.

Methods

This is a cluster randomised, controlled trial investigating the clinical use and cost-effectiveness of a digitally supported care management programme for caregivers of people with dementia (PwD). Five hundred family caregivers will be randomised at GP offices, specialist practices and memory clinics, with about n=250 participants per arm. Participants are eligible if they are the primary family caregiver of a PwD, are at least 18 years of age and provide informed consent. Participants in the intervention group will receive an individualised care management plan, which will be carried out by qualified study nurses in collaboration with the treating GP. All participants will receive a baseline assessment and a 6-months follow-up assessment. Participants in the wait-list control group will receive usual care. Starting at the 6 months’ follow-up, the former controls will also receive an individualised management plan. Primary outcomes are the number of unmet needs (incl. the Camberwell Assessment of Need for the Elderly, CANE) and health-related quality of life (EQ-5D-5L) at 6 months. Secondary outcomes include caregiver burden (Zarit Burden Interview, ZBI), social support (Lubben Social Network Scale, LSNS), the use of medical and non-medical services (Questionnaire for the Use of Medical and Non-Medical Services, FIMA) and resource utilisation (Resource Utilisation in Dementia, RUD). The primary analysis will be based on intention-to-treat. Between- and within-group analyses and a cost-effectiveness analysis will be conducted to estimate the effect of the tablet PC-based care management programme. This trial is funded by the German Federal Joint Committee (G-BA) Innovation Fund.

Discussion

The findings of this trial will be useful in informing and improving current healthcare system structures and processes to support family dementia caregivers within routine care practices.

Trial registration

ClinicalTrials.gov NCT04037501. Registered on 30 July 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05290-w.

Indo-European origins: a computer-simulation test of five hypotheses

Allele frequency distributions were generated by computer simulation of five models of microevolution in European populations. Genetic distances calculated from these distributions were compared with observed genetic distances among Indo-European speakers. The simulated models differ in complexity, but all incorporate random genetic drift and short-range gene flow (isolation by distance). The best correlations between observed and simulated data were obtained for two models where dispersal of Neolithic farmers from the Near East depends only on population growth. More complex models, where the timing of the farmers' expansion is constrained by archaeological time data, fail to account for a larger fraction of the observed genetic variation; this is also the case for a model including late Neolithic migrations from the Pontic steppes. The genetic structure of current populations speaking Indo-European languages seems therefore to largely reflect a Neolithic expansion. This is consistent with the hypothesis of a parallel spread of farming technologies and a proto-Indo-European language in the Neolithic. Allele-frequency gradients among Indo-European speakers may be due either to incomplete admixture between dispersing farmers, who presumably spoke proto-Indo-European, and pre-existing hunters and gatherers (as in the traditional demic diffusion hypothesis), or to founder effects during the farmers' dispersal. By contrast, successive migrational waves from the East, if any, do not seem to have had genetic consequences detectable by the present comparison of observed and simulated allele frequencies.

Genetic variation in North Africa and Eurasia: neolithic demic diffusion vs. Paleolithic colonisation

The hypothesis that both genetic and linguistic similarities among Eurasian and North African populations are due to demic diffusion of neolithic farmers is tested against a wide database of allele frequencies. Demic diffusion of farming and languages from the Near East should have determined clines in areas defined by linguistic criteria; the alternative hypothesis of cultural transmission does not predict clines. Spatial autocorrelation analysis shows significant gradients in three of the four linguistic families supposedly affected by neolithic demic diffusion; the Afroasiatic family is the exception. Many such gradients are not observed when populations are jointly analyzed, regardless of linguistic classification. This is incompatible with the hypothesis that major cultural transformations in Eurasia (diffusion of related languages and spread of agriculture) took place without major demographic changes. The model of demic diffusion seems therefore to provide a mechanism explaining coevolution of linguistic and biological traits in much of the Old World. Archaeological, linguistic, and genetic evidence agree in suggesting a multidirectional process of gene flow from the Near East in the neolithic. However, the possibility should be envisaged that some allele frequency patterns can predate the neolithic and depend on the initial spread of Homo sapiens sapiens from Africa into Eurasia.

Genetic evidence on origin and dispersal of human populations speaking languages of the Nostratic macrofamily

Contemporary patterns of allele frequencies allow inferences on past evolutionary processes. L.L. CavalliSforza [(1988) Munibe 6, 129-137] and C. Renfrew [(1991) Cambridge Archaeol. J. 1, 3-23] proposed that neolithic farmers from the Near East propagated a group of related ancestral languages, from which three or four linguistic families developed. Here we show that genetic variation among Indo-European, Elamo-Dravidian, and Altaic speakers (grouped by some linguists in the Nostratic macrofamily) supports this hypothesis, whereas the evidence on Afro-Asiatic speakers is ambiguous. Gene-frequency clines within these linguistic families suggest that language diffusion was largely associated with population movements rather than with purely cultural transmission. Archeological, linguistic, and genetic evidence can be reconciled by envisaging a process of population growth and multidirectional dispersal from the Near East as the main factor shaping genetic and linguistic diversity in Eurasia and perhaps in North Africa.

Spatial patterns of human gene frequencies in Europe

The aims of this study of spatial patterns of human gene frequencies in Europe are twofold. One is to present new methodology developed for the analysis of such data. The other is to report on the diversity of spatial patterns observed in Europe and their interpretation as evidence of population processes. Spatial variation in 59 allele and haplotype frequencies (26 genetic systems) for polymorphisms in blood antigens, enzymes, and proteins is analyzed for an aggregate of 3,384 localities, using homogeneity tests, one-dimensional and directional spatial correlograms, and SYMAP interpolated surfaces. The data matrices are reduced to reveal the principal patterns by clustering techniques. The findings of this study can be summarized as follows: 1) There is significant heterogeneity in allele frequencies among the localities for all but one genetic system. 2) There are significant spatial patterns for most allele frequencies. 3) There is a substantial minority of clinal patterns in these populations. Clinal trends are found more frequently in HLA alleles than for other variables. North-south and northwest-southwest gradients predominate. 4) There is a strong decline in overall genetic similarity with geographic distance for most variables. 5) There are few, if any, appreciable correlations in pairs of allele frequencies over the continent, and there is little interesting correlation structure in the resulting correlation matrix. 6) Few spatial correlograms are markedly similar to each other, yet they form well-defined clusters. Spatial variation patterns, therefore, differ among allele frequencies. Patterns of human gene frequencies in modern Europe are diverse and complex. No single model suffices for interpretation of the observed genetic structure. Some clinal patterns reported here support the Neolithic demic-expansion hypothesis, others suggest latitudinal selection. Most of the clinal patterns are in HLA alleles, but there is also evidence from ABO for east-west migration diffusion. The majority of patterns are patchy, consistent with hypotheses of isolation by distance or of settlement of genetically differing, subsequently expanding ethnic groups. While undoubtedly there has been an ongoing stochastic process of differentiation consistent with the isolation-by-distance model, this has not obscured the directional patterns caused by migration (demic diffusion), and has perhaps only reinforced the contribution from settlement of ethnic units to patterns of genetic variation. However, the impact of the latter is most difficult to discern and requires further methodological developments.

Inferences on the inheritance of congenital anomalies from temporal and spatial patterns of occurrence

Most congenital anomalies are believed to result from interactions between genetic and environmental determinants, whose relative importance is not generally established. Temporal and spatial patterns allow inferences on the underlying transmission processes; in particular, it is possible to discriminate between sporadic and nonsporadic genetic factors, and to find evidence for the effects of environmental heterogeneity in time and space. We studied the occurrence of 14 anomalies in 14 registries of Western Europe. Four basic patterns have been identified: (1) Chromosomal abnormalities have uniform incidences and do not show significant geographical variation, in agreement with the expected consequences of randomly scattered nondisjunction events. (2) The homogeneous spatial distributions of three severe malformations (renal agenesis, oesophageal atresia, ano-rectal atresia) are consistent with both the effects of fresh mutation and segregation of detrimental alleles. (3) A decrease of similarity of incidences with distance has been observed for neural tube defects, and this is the expected consequence of isolation by distance on genetically determined traits. (4) For facial clefts, polydactyly, and hypospadias, all postulated processes poorly account for the observed temporal and spatial patterns.

Diversity of some gene frequencies in European and Asian populations. IV. Genetic population structure assessed by the variogram

Isolation-by-distance models of population structure predict an exponential decrease of genetic relatedness with distance. Under the Kimura-Weiss (1964) model the plots of gene frequency variance versus distance (variograms), computed at various loci, are expected to have equal slope and reach a common asymptote. The gene frequency distributions at eight loci in 192 European and Asian populations have been summarized by variograms. On the average, the Kimura-Weiss model seems to describe adequately allele frequency change up to 900 km, but gradients are apparent at greater distances for most markers studied. These patterns may result form either differential selection or long-range gene flow; however, the extensive clinal variation observed for glyoxalase, esterase D and 6-PGD cannot be entirely accounted for by the Neolithic radiation of early farmers in the Middle East and Europe.