Patterns of twinning for Swedish women, 1961-1999

The Nordic population registers provide a unique possibility to study the demographic behavior of small population groups and rare events. In this paper, we study the childbearing behavior of Swedish mothers of twins between 1961 and 1999, inclusive. The twinning rate has increased since the mid-1970s in response to a growing use of fertility-stimulating treatments such as in-vitro fertilization. Such medical procedures are applied mainly to women beyond prime childbearing ages. Nevertheless, we find no simple age pattern in twinning rates. They do not just increase with the woman´s age. Our most consistent finding is that mothers of twins wait noticeably longer than women with singletons before they have another child. This apart, mothers with twins at their first birth have next-birth fertility patterns very similar to women who have two singletons at their first two births. This commonality in childbearing behavior does not extend to higher-order births, though. For mothers with a singleton and a pair of twins, the progression to a third birth depends very much on whether the twins came first or second. We also discover that at parities beyond 3, twinning rates increase with parity, especially at very short durations since the previous birth.vital events

Childbearing patterns for Swedish mothers of twins, 1961-1999

The Nordic population registers provide a unique possibility to study the demographic behavior of very small population groups and rare events. In this paper, we study the childbearing behavior of Swedish mothers of twins between 1961 and 1999, inclusive. Our most consistent finding is that mothers of twins wait noticeably longer than women with singletons before they have another child. This apart, mothers with twins at their first birth have next-birth fertility patterns very similar to women who have two singletons at their first two births. This commonality in child-bearing behavior does not extend to higher-order births. For mothers with a singleton and a pair of twins, the progression to a third birth depends very much on whether the twins came first or second. Beside these main results our fascinating material also provides a number of descriptive findings. The Swedish twinning rate has increased since the mid-1970s in response to a growing use of fertility-stimulating treatments such as in-vitro fertilization, in parallel with similar developments in many other countries. Such medical procedures are applied mainly to women beyond prime childbearing ages. Nevertheless, we find no simple age pattern in twinning rates. Even in recent years they do not just in-crease with the woman’s age. By way of contrast, at parities beyond 3 twinning rates increase with parity when we control for calendar period, time since last previous birth, and (NB) the woman’s own age.Sweden, twin studies

Childbearing patterns for Swedish mothers of twins, 1961-1999

The Nordic population registers provide a unique possibility to study the demographic behavior of very small population groups and rare events. In this paper, we study the childbearing behavior of Swedish mothers of twins between 1961 and 1999, inclusive. Our most consistent finding is that mothers of twins wait noticeably longer than women with singletons before they have another child. This apart, mothers with twins at their first birth have next-birth fertility patterns very similar to women who have two singletons at their first two births. This commonality in child-bearing behavior does not extend to higher-order births. For mothers with a singleton and a pair of twins, the progression to a third birth depends very much on whether the twins came first or second. Beside these main results our fascinating material also provides a number of descriptive findings. The Swedish twinning rate has increased since the mid-1970s in response to a growing use of fertility-stimulating treatments such as in-vitro fertilization, in parallel with similar developments in many other countries. Such medical procedures are applied mainly to women beyond prime childbearing ages. Nevertheless, we find no simple age pattern in twinning rates. Even in recent years they do not just in-crease with the woman’s age. By way of contrast, at parities beyond 3 twinning rates increase with parity when we control for calendar period, time since last previous birth, and (NB) the woman’s own age

Patterns of twinning for Swedish women, 1961-1999

The Nordic population registers provide a unique possibility to study the demographic behavior of small population groups and rare events. In this paper, we study the childbearing behavior of Swedish mothers of twins between 1961 and 1999, inclusive. The twinning rate has increased since the mid-1970s in response to a growing use of fertility-stimulating treatments such as in-vitro fertilization. Such medical procedures are applied mainly to women beyond prime childbearing ages. Nevertheless, we find no simple age pattern in twinning rates. They do not just increase with the woman's age. Our most consistent finding is that mothers of twins wait noticeably longer than women with singletons before they have another child. This apart, mothers with twins at their first birth have next-birth fertility patterns very similar to women who have two singletons at their first two births. This commonality in childbearing behavior does not extend to higher-order births, though. For mothers with a singleton and a pair of twins, the progression to a third birth depends very much on whether the twins came first or second. We also discover that at parities beyond 3, twinning rates increase with parity, especially at very short durations since the previous birth

Patterns of twinning for Swedish women, 1961-1999

'The Nordic population registers provide a unique possibility to study the demographic behavior of small population groups and rare events. In this paper, we study the childbearing behavior of Swedish mothers of twins between 1961 and 1999, inclusive. The twinning rate has increased since the mid-1970s in response to a growing use of fertility-stimulating treatments such as in-vitro fertilization. Such medical procedures are applied mainly to women beyond prime childbearing ages. Nevertheless, we find no simple age pattern in twinning rates. They do not just increase with the woman's age. Our most consistent finding is that mothers of twins wait noticeably longer than women with singletons before they have another child. This apart, mothers with twins at their first birth have next-birth fertility patterns very similar to women who have two singletons at their first two births. This commonality in childbearing behavior does not extend to higher-order births, though. For mothers with a singleton and a pair of twins, the progression to a third birth depends very much on whether the twins came first or second. We also discover that at parities beyond 3, twinning rates increase with parity, especially at very short durations since the previous birth.' (author's abstract)Die nordischen Bevoelkerungsregister bieten eine einzigartige Moeglichkeit, das demografische Verhalten kleiner Bevoelkerungsgruppen und seltener Ereignisse naeher zu untersuchen. Im vorliegenden Arbeitspapier wird das Geburtenverhalten von schwedischen Muettern von Zwillingen im Zeitraum 1961 bis 1999 analysiert. Die Geburtenrate von Zwillingen ist allgemein seit Mitte der 70er Jahre durch eine zunehmende Anwendung von fruchtbarkeitsfoerdernden Methoden, wie die In-Vitro-Fertilisation, gestiegen. Obwohl solche medizinischen Massnahmen meist bei Frauen, die das geburtsfaehige Alter ueberschritten haben, angewandt werden, kann nach den Ergebnissen kein einfaches Altersmuster bei den Zwillingsraten festgestellt werden. Diese steigen nicht automatisch mit dem Alter der Frau an. Hingegen wird festgestellt, dass Muetter von Zwillingen im Unterschied zu Muettern von Einzelkindern deutlich laenger warten, bevor sie sich fuer die Geburt eines weiteren Kindes entscheiden. Fuer Muetter mit einem Einzelkind und einem Zwillingspaar haengt die Entscheidung fuer eine dritte Geburt wesentlich davon ab, ob die Zwillinge an erster oder an zweiter Stelle zur Welt gekommen sind. (ICIUebers)German title: Muster von Zwillings-Geburten bei schwedischen Muettern 1961-1999Available from http://www.demogr.mpg.de/papers/working/wp-2002-031.pdf / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Delprogrammet cancerframkallande ämnen i tätortsluft, personlig exponering och bakgrundsmätningar. : Utveckling av metoder för personburen mätning av PAH.

I denna studie har olika metoder för analys av partikulära polycykliska aromatiska kolväten (PAH) efter provtagning på filter utvärderats. Två metoder för ultraljudsextraktion, ett traditionellt ultraljudsvattenbad samt en ultraljudsextraktor specialdesignad för PAH-extraktion (Sonicator) samt två olika analysmetoder gaskromatografi-masspektrometri (GC/MS) och vätskekromatografi med fluorescensdetaktion (LC/Fluo) har studerats. För testerna användes bl.a certifierade referensmaterial av typen Urban Dust och Fly Ash. Sonicatorn gav för Urban Dust en avvikelse på mellan 5-35 % med GC/MS-analys och med LC/Fluo-analys var avvikelsen endast 3 % från det certifierade värdet. För extraktion av Fly Ash med Sonicatorn var avvikeslen <10 % med GC/MS-metoden medan LC/Fluo-metoden endast var ca 30 % av det certifierade värdet, vilket inte är acceptabelt. Extraktion med traditionellt ultraljudsvattenbad följt av LC/Fluo-analys gav för Urban Dust en avvikelse på ca 32%. Filterprover tagna i stadsmiljö analyserade med bägge metoderna gav likvärdiga resultat för B[a]P oberoende av analysmetod. Studien visar att båda analysmetoderna är användbara för mätningar där dammet är av typen Urban Dust, dvs. från utomhus- och tätortsmiljöer. I denna studie har fokus legat på analys av högmolekylära, partikulära PAH-komponenter och då framför allt B[a]P. Förutom B[a]P kan flertalet andra PAH-komponenter analyseras med bägge metoderna, dock har i detta projekt endast B[a]P studerats med LC-fluo-metoden eftersom detta ämne är prioriterat i EU-direktiven. En stor fördel med LC/Fluo-metoden är att den inte kräver lika omfattande provupparbetning före analys. LC/Fluo-metoden har något bättre känslighet, men bägge metoderna är tillräckligt känsliga för dessa analyser. Det är viktigt att påpeka att PAH i allmänluften domineras av PAH med 3-4 ringar dvs PAH som finns i gasfas. PAH-komponenterna fenantren, pyren och fluoranten är till 80-90% i gas fas vid 20°C. Vill man mäta sanna halter av PAH i både gasfas och partikelfas måste någon form av denuder eller motsvarande provtagningsmetod användas. För att få en bra uppfattning om totala mängden gas + partiklar och en ungefärlig uppfattning om fördelning gas/partiklar kan en enkel uppsättning av 13-mm-filter av glasfiber i kombination med adsorbentrör med XAD-2 användas [9-10]. Denna provtagningsutrustning är lättanvänd för personburna mätningar där man inte specifikt behöver mäta PM2,5 och kan användas både för GC-MS-analys och LC-Fluo-analys [9-10]. Ett intressant alternativ för att mäta gasfas-PAH är passiva provtagningstekniker som PUF (polyurethane foam disks) och SPMDs (semipermeable membrane devices) som idag används som tidsintegrerade (2-6 veckor) semikvantitativa provtagare i olika miljöövervakningsprogram för gasfas PAH både i Europa och globalt [11-13]. Det är därför viktigt att också utveckla och validera enkla och billiga metoder och gärna diffusionsprovtagare för att kunna mäta gasfas-PAH både stationärt och personburet. Lagring av prover testades inte i denna studie. Vid långtidslagring kan det vara viktigt att lagra filtren i kylskåp. PAH-föreningar med 5 eller 6 ringar anses dock vara stabila även vid lagring i rumstemperatur [7]. Sammanfattningsvis har utvärderingen visat att det är möjligt att analysera 8 av de 16 PAH-föreningar som EPA anger på personburna teflonfilter provtagna med PM2.5cykloner. Inom HÄMI-luft programmet kan man därmed vid samma provtagningstillfälle få svar på partikelmassekoncentrationen och koncentrationen av ett flertal svårflyktiga PAH-föreningar, däribland benso(a)pyren

New insights into the genetic etiology of Alzheimer’s disease and related dementias

Characterization of the genetic landscape of Alzheimer’s disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/‘proxy’ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele