Lumbar disc herniation (LDH) is common and often debilitating. Microdiscectomy of herniated lumbar discs (LDHsurg) is performed on the most severe cases to resolve the resulting sciatica. Here we perform a genome-wide association study on 4,748 LDHsurg cases and 282,590 population controls and discover 37 highly correlated markers associating with LDHsurg at 8q24.21 (between CCDC26 and GSDMC), represented by rs6651255[C] (OR=0.81; P=5.6 × 10−12) with a stronger effect among younger patients than older. As rs6651255[C] also associates with height, we performed a Mendelian randomization analysis using height polygenic risk scores as instruments to estimate the effect of height on LDHsurg risk, and found that the marker's association with LDHsurg is much greater than predicted by its effect on height. In light of presented findings, we speculate that the effect of rs6651255 on LDHsurg is driven by susceptibility to developing severe and persistent sciatica upon LDH.

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In this study, we examined the prevalence of specific (dental) phobia among a sample of the Icelandic population. In addition to dental anxiety we explored factors that could be related to dental anxiety. In the period 1972-73, a stratified sample of 1641 schoolchildren in Reykjavík was selected for a study on malocclusion, dental maturation and other factors. Twenty-two years later (1995), a postal survey conducted in this group looked at many variables relating to oral health, including orofacial pain, functional oral disorders, self-perception of dental and general appearance and need for orthodontic treatment. Out of 1529 individuals contacted, 1192 completed questionnaires were returned (response rate 78%). Questions based on DSM-IV criteria of specific (dental) phobia (DP) were included. Ninety-six participants reported that they had avoided dental treatment during the previous 6 months. Twenty-one respondents fulfilled DSM-IV criteria for specific (dental) phobia (DP) and 75 admitted to many symptoms of dental anxiety (DA). Specific (dental) phobia (DP) was more prevalent among women than among men. The divorced or widowed were most at risk, as were non-salaried respondents. Most respondents attributed the onset of their phobias to a specific painful or fearful experience. There was a significant difference between the total dentally anxious (TDA = DA + DP) and the not dentally anxious (NDA) with regard to sex (women--higher TDA) and marital status (divorced or widowed--higher TDA). The TDA had statistically fewer teeth than the NDA and received dental treatment less frequently.

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