[Breastfeeding in Iceland: Changes in prevalence and duration over a century].

INTRODUCTION: Worldwide, the health-promoting effects of breastfeeding on children and their mothers are indisputable. The frequency and duration of breastfeeding varies greatly internationally but studies on prevalence and influencing factors of breastfeeding in Iceland are scanty and the published ones deal with small groups. The aim of this research is to describe the epidemiology of breastfeeding duration and its influencing factors in Iceland among a large cohort in a whole population over almost one century. MATERIAL AND METHODS: This is a historical cohort study, using data from The Cancer Detection Clinic Cohort of The Icelandic Cancer Society, collected retrospectively by questionnaires during the years 1964-2008. The data consisted of mothers´ reported information on breastfeeding of their 81,889 children, 36,537 first-borns and 45,352 younger siblings. The frequency and duration of breastfeeding was calculated and the effects of the following exposure variables were assessed: Maternal age, BMI (N=4950, data collected 1979-2008) and smoking (N=32.087, data collected 1995-2008), the child's year of birth and its order in the sibling group. RESULTS: The children were born in the period of 1917-2008. In the late 1970s, the average duration of breastfeeding began to increase, in all age groups of mothers, increasing rapidly from 3 months to 7-8 months. At about the same time, the breastfeeding duration increased depending on the birth order of the children, younger children were breastfed for longer than their older siblings. Women with normal weight (BMI 18.5 to 24.9) breastfed their babies the longest, while obese women breastfed the shortest. Women with any history of smoking reported shorter duration of breastfeeding than women who had never smoked. CONCLUSION: The increase in the average duration of breastfeeding in Iceland a few decades ago is in accordance with the information in the World Health Organization's database from European countries 1975-2000, where the Nordic countries and most Northern European countries promoted breastfeeding at a similar time. High BMI and maternal smoking are important variables when studying breastfeeding and this study indicates their negative association with the duration of breastfeeding.

A genetic risk factor for periodic limb movements in sleep.

BACKGROUND: The restless legs syndrome (RLS) is a common neurologic disorder characterized by an irresistible urge to move the legs. It is a major cause of sleep disruption. Periodic limb movements in sleep are detectable in most patients with RLS and represent an objective physiological metric. METHODS: To search for sequence variants contributing to RLS, we performed a genomewide association study and two replication studies. To minimize phenotypic heterogeneity, we focused on patients with RLS who had objectively documented periodic limb movements in sleep. We measured serum ferritin levels, since iron depletion has been associated with the pathogenesis of RLS. RESULTS: In an Icelandic discovery sample of patients with RLS and periodic limb movements in sleep, we observed a genomewide significant association with a common variant in an intron of BTBD9 on chromosome 6p21.2 (odds ratio, 1.8; P=2x10(-9)). This association was replicated in a second Icelandic sample (odds ratio, 1.8; P=4x10(-4)) and a U.S. sample (odds ratio, 1.5; P=4x10(-3)). With this variant, the population attributable risk of RLS with periodic limb movements was approximately 50%. An association between the variant and periodic limb movements in sleep without RLS (and the absence of such an association for RLS without periodic limb movements) suggests that we have identified a genetic determinant of periodic limb movements in sleep (odds ratio, 1.9; P=1x10(-17)). Serum ferritin levels were decreased by 13% per allele of the at-risk variant (95% confidence interval, 5 to 20; P=0.002). CONCLUSIONS: We have discovered a variant associated with susceptibility to periodic limb movements in sleep. The inverse correlation of the variant with iron stores is consistent with the suspected involvement of iron depletion in the pathogenesis of the disease.

Initiation of complementary feeding and duration of total breastfeeding: unlimited access to lactation consultants versus routine care at the well-baby clinics.

INTRODUCTION: Breastfeeding has several advantages for both mother and child. Lactation consultants may promote prolonged breastfeeding, but little is known about their impact on the initiation of complementary feeding. SUBJECTS AND METHODS: Dietary intake during the initial complementary feeding period from 5 to 6 months was collected on mother-infant pairs who had unlimited access to lactation consultants along with those mother-infant pairs who received routine care at the well-baby clinics. The total duration of breastfeeding in each study population was also recorded, and total breastfeeding durations of infants receiving complementary foods from 4 months and those exclusively breastfed for 6 months in each of the two study populations were compared. RESULTS: Higher proportion of infants of mothers with unlimited access to lactation consultants were fed vegetable and vegetable purées (p=0.05) and more than one food type (p=0.05) at 5 months. Furthermore, a lower percentage of them had three meals per day at 6 months (p=0.001) compared with those receiving routine care at the well-baby clinics. Infants exclusively breastfed for 6 months all had similar duration of total breastfeeding. CONCLUSIONS: Mother-infant pairs with unlimited access to lactation consultant had slower introduction of complementary foods at the initial complementary feeding period, according to number of infant's meals at 6 months of age. Furthermore, those exclusively breastfed for 6 months had more prolonged breastfeeding compared with mothers who began complementary feeding at 4 months regardless of exposure to lactation consultants.