Hearing impairment is common among Saami adults in Northern Finland.

The Saami are the only indigenous population in Europe and their traditional living area is northern Scandinavia. Hearing impairment (HI) among Saami has not been studied before. The objective was to investigate the presence and type of HI among Saami adults, aged 49-77 years (median age 61 years), living in northern Finland. In addition, the presence of self-reported hearing difficulties, difficulties to hear in background noise and tinnitus were studied. An epidemiological, cross-sectional study encompassing a structured interview, otological examination and audiometry was performed. Bilateral HI was present in 42.9% of men and 29.4% of women, when HI was defined as a pure tone average (PTA) of at least 20 dB hearing level (HL) or more at the frequencies of 0.5, 1, 2 and 4 kHz. In one or both ears (worse ear hearing level, WEHL0.5,1,2,4≥20 dB HL) HI was present in 61.8% of men and 42.2% of women. Sensorineural high frequency hearing impairment was found to be most common. Nearly half (46.9%) of the study subjects reported hearing problems and more than half (55.6%) reported difficulties in following conversation in background noise. Measured HI and subjective hearing difficulties are common among the Saami adults. The healthcare personnel working in this area should be aware of the hearing problems of the Saami population. ABBREVIATIONS: ARHI, Age-related hearing impairment; PTA, Pure tone average; HI, Hearing impairment; HL, Hearing level; BEHL, Better ear hearing level; WEHL, Worse ear hearing level; CI, Confidence interval.

A genome-wide analysis of population structure in the Finnish Saami with implications for genetic association studies.

The understanding of patterns of genetic variation within and among human populations is a prerequisite for successful genetic association mapping studies of complex diseases and traits. Some populations are more favorable for association mapping studies than others. The Saami from northern Scandinavia and the Kola Peninsula represent a population isolate that, among European populations, has been less extensively sampled, despite some early interest for association mapping studies. In this paper, we report the results of a first genome-wide SNP-based study of genetic population structure in the Finnish Saami. Using data from the HapMap and the human genome diversity project (HGDP-CEPH) and recently developed statistical methods, we studied individual genetic ancestry. We quantified genetic differentiation between the Saami population and the HGDP-CEPH populations by calculating pair-wise F(ST) statistics and by characterizing identity-by-state sharing for pair-wise population comparisons. This study affirms an east Asian contribution to the predominantly European-derived Saami gene pool. Using model-based individual ancestry analysis, the median estimated percentage of the genome with east Asian ancestry was 6% (first and third quartiles: 5 and 8%, respectively). We found that genetic similarity between population pairs roughly correlated with geographic distance. Among the European HGDP-CEPH populations, F(ST) was smallest for the comparison with the Russians (F(ST)=0.0098), and estimates for the other population comparisons ranged from 0.0129 to 0.0263. Our analysis also revealed fine-scale substructure within the Finnish Saami and warns against the confounding effects of both hidden population structure and undocumented relatedness in genetic association studies of isolated populations.

A genome-wide association study for age-related hearing impairment in the Saami.

This study aimed at contributing to the elucidation of the genetic basis of age-related hearing impairment (ARHI), a common multifactorial disease with an important genetic contribution as demonstrated by heritability studies. We conducted a genome-wide association study (GWAS) in the Finnish Saami, a small, ancient, genetically isolated population without evidence of demographic expansion. The choice of this study population was motivated by its anticipated higher extent of LD, potentially offering a substantial power advantage for association mapping. DNA samples and audiometric measurements were collected from 352 Finnish Saami individuals, aged between 50 and 75 years. To reduce the burden of multiple testing, we applied principal component (PC) analysis to the multivariate audiometric phenotype. The first three PCs captured 80% of the variation in hearing thresholds, while maintaining biologically important audiometric features. All subjects were genotyped with the Affymetrix 100 K chip. To account for multiple levels of relatedness among subjects, as well as for population stratification, association testing was performed using a mixed model. We summarised the top-ranking association signals for the three traits under study. The top-ranked SNP, rs457717 (P-value 3.55 x 10(-7)), was associated with PC3 and was localised in an intron of the IQ motif-containing GTPase-activating-like protein (IQGAP2). Intriguingly, the SNP rs161927 (P-value 0.000149), seventh-ranked for PC1, was positioned immediately downstream from the metabotropic glutamate receptor-7 gene (GRM7). As a previous GWAS of a European and Finnish sample set already suggested a role for GRM7 in ARHI, this study provides further evidence for the involvement of this gene.

Genome-wide SNP analysis reveals no gain in power for association studies of common variants in the Finnish Saami.

The Saami from Fennoscandia are believed to represent an ancient, genetically isolated population with no evidence of population expansion. Theoretical work has indicated that under this demographic scenario, extensive linkage disequilibrium (LD) is generated by genetic drift. Therefore, it has been suggested that the Saami would be particularly suited for genetic association studies, offering a substantial power advantage and allowing more economic study designs. However, no study has yet assessed this claim. As part of a GWAS for a complex trait, we evaluated the relative power for association studies of common variants in the Finnish Saami. LD patterns in the Saami were very similar to those in the non-African HapMap reference panels. Haplotype diversity was reduced and, on average, levels of LD were higher in the Saami as compared with those in the HapMap panels. However, using a 'hidden' SNP approach we show that this does not translate into a power gain in association studies. Contrary to earlier claims, we show that for a given set of common SNPs, genomic coverage attained in the Saami is similar to that in the non-African HapMap panels. Nevertheless, the reduced haplotype diversity could potentially facilitate gene identification, especially if multiple rare variants play a role in disease etiology. Our results further indicate that the HapMap is a useful resource for genetic studies in the Saami.