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Even though sunlight is viewed as the most important determinant of 25-hydroxyvitamin D (25(OH)D) status, several European studies have observed higher 25(OH)D concentrations among north-Europeans than south-Europeans. We studied the association between geographical latitude (derived from ecological data) and 25(OH)D status in six European countries using harmonised immunoassay data from 81 084 participants in the Biomarkers for Cardiovascular Risk Assessment in Europe (BiomarCaRE) project (male sex 48·9 %; median age 50·8 years; examination period 1984–2014). Quantile regression models, adjusted for age, sex, decade and calendar week of sampling and time from sampling to analysis, were used for between-country comparisons. Up until the median percentile, the ordering of countries by 25(OH)D status (from highest to lowest) was as follows: Sweden (at 65·6–63·8°N), Germany (at 48·4°N), Finland (at 65·0–60·2°N), Italy (at 45·6–41·5°N), Scotland (at 58·2–55·1°N) and Spain (at 41·5°N). From the 75th percentile and upwards, Finland had higher values than Germany. As an example, using the Swedish cohort as a comparator, the median 25(OH)D concentration was 3·03, 3·28, 5·41, 6·54 and 9·28 ng/ml lower in the German, Finnish, Italian, Scottish and Spanish cohort, respectively (P -value < 0·001 for all comparisons). The ordering of countries was highly consistent in subgroup analyses by sex, age, and decade and season of sampling. In conclusion, we confirmed the previous observation of a north-to-south gradient of 25(OH)D status in Europe, with higher percentile values among north-Europeans than south-Europeans. [ABSTRACT FROM AUTHOR]

Aim: A high participation rate is considered as a prerequisite for representative survey results, especially when it is known that non-participation is selective. In many countries migration is increasing and the proportion of people speaking other language(s) than the official language(s) of the country is also increasing. How does this affect survey participation rates? Methods: Data from four cross-sectional health examination surveys (the FINRISK Study) were used to evaluate the effect of the registered mother tongue to participation in the survey. Results: Finland has two official languages (Finnish and Swedish). Between 1997 and 2012, the proportion of the population with some other language as their registered mother tongue has increased significantly. Participation rates in the health surveys have been highest among the Finnish language group (68% in men in 1997 and 76% in women in 1997), while lowest among the foreign language group (43% in men in 1997 and 57% in women in 1997). In 2012, the participation rates had declined in all language groups: for men, 58%, 62% and 41% for Finnish, Swedish and foreign groups respectively, and for women 68%, 75% and 56%. Conclusions: The participation rate for the foreign language group was significantly lower than for the Finnish and Swedish groups. In future surveys it will be important to include actions to promote participation, e.g. providing survey material in several languages. These actions will increase costs but will be essential to ensure high participation rates and reliable results for the total population. [ABSTRACT FROM AUTHOR]