Einkenni mjaðmabrotahóps meðal eldri einstaklinga í sjálfstæðri búsetu

Abstract Background: Hip fractures in older adults are strongly associated with reduced health and quality of life. Loss of bone mass, physical function and muscle mass are thought to be main causes of hip fractures at older age. Associations between vitamin D status and bone mineral density (BMD) and hip-fractures have also been extensively explored in epidemiological studies. The observed strength for the association between vitamin D status and hip fractures often appears stronger than what would be expected by associations reported between vitamin D status and BMD alone. Fewer studies have, however, examined the possible role of factors reflecting physical function and mobility at older age in relation to hip-fractures. That is, factors that may be modifiable through healthy diet and physical exercise. Aims: To characterize differences between older adults that experience hip fractures compared to those who do not, with an emphasis on measures of bone mass on one hand and physical function on the other. Furthermore, to determine to what extent measures of volumetric BMD (vBMD) of the femoral neck and physical function may be associated with vitamin D status. Results: In paper-I baseline (2002-2006) characteristics of those who experienced hip fractures over the follow-up period (until 2012) versus those who did not were compared. Males that experienced hip fractures had significantly poorer measures of physical function, including performance in balance test and the time up and go test compared to males that did not experience hip fracture. These differences were still significant after adjustment for age and vBMD. Similar differences were not observed in females. In contrast, female hip fracture cases had lower body mass index, fat- and fat free mass compared to those that did not experience hip fractures. However, similarities between both sexes included lower vitamin D status (~5 nmol/L lower concentration of serum 25(OH)D), and lower leg strength among hip fracture cases compared to non-cases. In paper II the association between vitamin D status and vBMD at baseline as well as incident hip fractures were explored, taking measures of physical function into consideration as possible explanatory factors. After adjustment for age and BMI, deficient (serum 25(OH)D concentrations <30 nmol/L) compared to sufficient status (≥50 nmol/L) vitamin D was associated with lower vBMD of the femoral neck at baseline in both males -17 mg/cm3 vi (95% confidence interval (CI): -26, -8) and females -7 mg/cm3 (95%CI: -14, - 1). Deficient versus sufficient vitamin D status was also significantly associated with higher risk of incident hip fractures in males [Hazard ratio (HR): 3.1 (95%CI: 1,9, 5.2)] and females [1.8 (95%CI: 1.3, 2.5)]. After further adjustment for vBMD and measures of physical function the association became non-significant for males [HR: 1.3 (95%CI: 0.6, 2.5)] but remained significant for females [HR: 1.7 (1.1, 2.4)]. Further analyses suggested that these sex specific differences might relate to lower bone mass among females due to smaller bone volume that made the adjustment of vBMD and physical function less influential for females. In the third and final paper, the association between consumption of milk and cultured milk products with incident hip fractures was explored. Those participants who consumed less than half a portion of milk products per day (one portion ~250 mL) had significantly higher risk of incident hip fractures compared to those consuming ≥2 portions per day [HR 1.46 (95%CI 1.01, 2.11)], which is the amount that official dietary recommendations advocate. Conclusions: Sex specific differences were observed between hip fracture cases and non-cases. Measures of physical function and balance were more pronounced for males, while measures of body composition were more pronounced for females. Vitamin D status and consumption of milk and cultured milk products showed a relatively strong and protective association with incident hip fractures in Icelandic older adults. The possible causes for these observed associations appeared to differ between males and females.Ágrip Bakgrunnur: Mjaðmabrot fela í sér verulega skerðingu á heilsu og lífsgæðum. Orsakaþættir mjaðmabrota meðal aldraða eru m.a aukið tap á beinmassa, hreyfifærni og vöðvamassa með hækkandi aldri. Tengsl D vítamíns búskaps við styrk beina og mjaðmabrota hafa verið skoðuð ítarlega í fyrri rannsóknum. Þau tengsl virðast oft sterkari en búast mætti við út frá tengslum D vítamíns við beinþéttni. Færri rannsóknir hafa hins vegar verið gerðar sem skoða tengsl hreyfigetu við mjaðmabrot. Þ.e.a.s. færni sem að hluta til er hægt að hafa áhrif á með réttu mataræði og hreyfingu. Markmið: Að kortleggja hvað einkennir aldraða einstaklinga sem mjaðmabrotna frá þeim sem brotna ekki með áherslu á að skoða áhættuþætti sem tengjast skertri beinþéttni annars vegar og skertri hreyfigetu hins vegar; og meta hvernig þessir þættir tengjast D vítamín hag þátttakenda. Aðferðir: Notast var við gögn úr Öldrunarrannsókn Hjartaverndar (AGESReykjavík) sem samanstendur af 5764 þátttakendum sem skráðir voru í rannsóknina á árunum 2002 til 2006. Umfangsmiklum upplýsingum um heilsu og lífstíl þátttakenda var safnað við skráningu; þar á meðal mælingum á beinþéttni og mælingum á D vítamínhag í blóði, ásamt öðrum lífmerkjum. Upplýsingum um mjaðmabrot til loka árs 2012 var safnað úr sjúkraskrám. Niðurstöður: Grein 1: Einkenni þátttakenda í Öldrunarrannsókn Hjartaverndar við upphaf rannsóknar (2002-2006) voru skoðuð með m.t.t. líkamssamsetningar, mælinga á hreyfifærni, styrkleika, D vítamín hag í blóði ásamt öðrum lífmerkjum. Þær mælingar voru bornar saman milli þátttakenda sem mjaðmabrotnuðu eða brotnuðu ekki á meðan eftrirfylgni stóð (til loka 2012). Það sem einkenndi karlmenn sem brotnuðu var marktæk skert hreyfigeta við upphaf rannsóknar sem kom fram í verri gildum við mælingum á jafnvægi og hraða í svokölluðu “Timed Up and Go“ prófi. Einnig var styrkur í lærlegg minni meðal karlmanna sem brotnuðu. Þessi munur var greinilegur þó leiðrétt væri fyrir bæði aldri og beinþéttni við upphaf rannsóknar. Það sem einkennir konur sem mjaðmabrotna var marktækt lægri líkamsþyngdarstuðull, minni fitu- og vöðvamassi ásamt því að minni styrkur mældist í lærlegg. Styrkur D vítamíns í blóði (serum 25(OH)D) var marktækt lægri (~5 nmol/L) við upphaf rannsóknar hjá báðum kynjum sem brotnuðu. iv Grein 2: Hér voru tengsl D vítamín hags við upphaf rannsóknar skoðuð nánar með tilliti til beinþéttni annars vegar og mjaðmabrota hins vega ásamt því að taka þætti sem mæla hreyfigetu til greina. Eftir að hafa leiðrétt fyrir bæði aldri og líkamsþyngdarstuðli þá var ófullnægjandi D vítamín hagur í blóði við upphaf rannsóknar (