Physical capability, physical activity, and their association with femoral bone mineral density in adults aged 40 years and older: The Tromsø study 2015-2016

Since muscles can influence bone growth and vice versa, we examined if level of physical activity and physical capability tests can predict areal bone mineral density (aBMD). Both high activity level and good test performance were associated with higher aBMD, especially in women.

INTRODUCTION

Muscle influences bone formation and vice versa. Tests of physical capability and level of physical activity reflect various muscle qualities. We assessed the associations between total hip aBMD and physical activity as well as a range of standardized physical capability tests in an adult general population.

METHODS

A total of 3 533 women and men aged 40-84 years, participating in the population-based cross-sectional Tromsø study in Norway in 2015-2016, were included. Linear regression was used to assess associations between aBMD and physical activity and the physical capability tests grip strength, Timed Up and Go (TUG), Short Physical Performance Battery (SPPB), and standing balance. Non-linear associations were examined in cubic spline models. Standardized regression coefficients were calculated to compare effect sizes across physical capability measures.

RESULTS

In fully adjusted models, higher physical activity was positively associated with total hip aBMD in both sexes compared to a sedentary lifestyle. All tests of physical capability were associated with aBMD in women, SPPB showing the strongest association although effect sizes were too small to indicate clinically significant differences (1 point increase corresponded to an aBMD increase of 0.009 g/cm², CI = 0.005 to 0.012). In men, SPPB and its subtests were associated with aBMD with chair rises showing the strongest association (1 s increase in execution time corresponded to an aBMD decrease of 0.005 g/cm², CI = 0.008 to 0.002).

CONCLUSION

Physical activity was associated with aBMD, and tests of physical capability can account for some of the aBMD variations in adults aged 40 years and older, especially in women.

Does treatment with bisphosphonates protect against fractures in real life? The HUNT study, Norway

Bisphosphonates reduce fractures in randomized controlled trials (RCT); however, there is less information from real life. In our population including 14,990 women and 13,239 men, use of bisphosphonates reduced risk of fractures in hip and forearm in women. The magnitude of the effect was comparable to results from RCT.

INTRODUCTION

The objective was to examine if treatment with bisphosphonates (BPs) was associated with reduced risk of fractures in the hip and forearm in women and men in the general population.

METHODS

In a cohort study based on data from the third wave of the population-based HUNT Study (HUNT3), the fracture registry in Nord-Trøndelag, and the Norwegian Prescription Database, 14,990 women and 13,239 men 50-85 years were followed from the date of participating in HUNT3 (2006-2008) until the date of first fracture in the hip or forearm, death, or end of study (31 December 2012). Hazard ratios with 95% confidence intervals for hip and forearm fracture according to use of BPs were estimated using Cox proportional hazards models with time-dependent exposure. Adjustment for individual FRAX® fracture risk assessment scores was included.

RESULTS

BPs, predominantly alendronate, were used by 9.4% of the women and 1.5% of the men. During a median of 5.2 years of follow-up, 265 women and 133 men had a hip fracture, and 662 women and 127 men had a forearm fracture. Compared with non-users of BPs, the hazard ratios with 95% confidence interval for a fracture among users of BPs adjusted for age and FRAX® were 0.67 (0.52-0.86) for women and 1.13 (0.50-2.57) for men. Among users of glucocorticoids, the corresponding figures were 0.35 (0.19-0.66) and 1.16 (0.33-4.09), respectively.

CONCLUSIONS

Use of BPs was associated with reduced risk of fractures in hip and forearm in women, and the magnitude of effect is comparable to results from RCTs.

Contribution of elevation and residential proximity to the coast in explaining geographic variations in hip fracture incidence. A Norwegian Epidemiologic Osteoporosis Studies (NOREPOS) study

A higher risk of hip fracture was found in areas of Norway at higher elevation and farther from the coast. However, the previously seen county variations could not be explained by these geographical factors.

INTRODUCTION

Norway is an elongated country extending north of the Arctic Circle with substantial coast-inland variation in topography and climate. Differences in hip fracture incidence between counties and a distinct seasonal variation have previously been shown. The aim of the current study was to explore these variations further by considering associations of height above sea level (elevation) and distance to the coast with hip fracture incidence.

METHODS

All patients with hip fractures admitted to Norwegian hospitals in the period 2009-2018 were included. Individual residential elevation and distance to the coast was calculated in Geographic Information Systems and combined with individual-level population data on all Norwegians 50 years of age or older during the observation period, including hospital information on fractures. Age-standardized incidences rate and incidence rate ratios with 95% confidence intervals (IRR, 95% CI) according to elevation and coastal proximity were estimated. The associations were tested using Poisson models adjusting for sex, urban/rural location of residency, country of birth, and season of hip fracture occurrence.

RESULTS

From 2009 to 2018, there were 85,776 first hip fractures. There was an increasing risk with higher residential elevation (above versus below mean) for women: IRR = 1.04, 95% CI: 1.02, 1.05), but not for men (IRR = 1.00, 95% CI: 0.97, 1.02). Incidence of hip fracture increased with distance from the coast. Women residing the farthest away from the coast (above versus below mean distance) had a higher age-adjusted incidence of hip fracture compared to those living closer to the coast (IRR = 1.04 (95% CI: 1.02, 1.06), whereas no association was found in men (IRR = 1.00 (95% CI: 1.00, 1.01). Combining elevation and distance to coast showed a higher incidence in women living at high elevation far from the coast compared with women living at low elevation near the coast (IRR = 1.07, 95% CI: 1.04, 1.10). A similar result was found in men but only for hip fractures occurring during March-May (IRR = 1.07, 95% CI: 1.00, 1.15). The previously shown patterns of county differences and seasonal variations were unchanged when considering geography.

CONCLUSION

We found a somewhat higher incidence of hip fracture in inland residents living in areas of high elevation, as compared to those living in more coastal proximity; however, the geographic variation did not explain county and seasonal differences in fracture incidence in Norway. More in-depth analyses on temperature and climate factors may give further clues.

Geographic variations in hip fracture incidence in a high-risk country stretching into the Arctic: a NOREPOS study

There are geographic variations in hip fracture incidence rates across Norway, with a lower incidence in the coastal areas of the southwest and in the Arctic north, contrary to what may be expected with regard to vitamin D exposure from sunlight. The regional differences have become smaller in recent years.

INTRODUCTION

To investigate geographic variation in hip fracture incidence within Norway and regional differences in time trends.

METHODS

All hip fractures treated in Norwegian hospitals 2002-2013 were included, and demographic information was obtained from Statistics Norway. Age-standardized incidence rates were calculated separately for 19 counties. Incidence rate ratios with 95% confidence intervals for county differences and time trends were estimated using Poisson regression.

RESULTS

Age-standardized number of hip fractures per 10,000 person-years varied between counties from 69 to 84 in women and from 34 to 41 in men. The highest rates were observed in the southeastern capital city of Oslo, while rates were low in the four northernmost counties. There was an east-west gradient, with lower incidence in the coastal southwest compared with the southeast. Women showed a statistically significant decline during 2002-2013 in almost all counties (up to 31%). In men, only a few counties showed a decline. In both genders, hip fracture rates at age 80 in the combined five counties with the highest rates were significantly higher than in the combined five counties with the lowest rates across the period, although the trends converged over time.

CONCLUSIONS

In Norway, the hip fracture incidence was lower in the north compared with the south. In addition, we observed an east-west gradient with the highest incidence in the southeast and lower incidence in the coastal southwest. While there has been an overall declining trend in hip fracture incidence over time, regional differences are still apparent.

Grip strength in men and women aged 50-79 years is associated with non-vertebral osteoporotic fracture during 15 years follow-up: The Tromsø Study 1994-1995

In 50-79-year-olds who participated in the Tromsø Study (1994-1995), the risk of non-vertebral osteoporotic fractures during 15 years follow-up increased by 22% in men and 9% in women per 1 SD lower grip strength. The strongest association was observed in men aged 50-64 years.

INTRODUCTION

We aimed to explore whether low grip strength was associated with increased risk of non-vertebral osteoporotic fracture in the population-based Tromsø Study 1994-1995.

METHODS

Grip strength (bar) was measured by a Martin Vigorimeter and fractures were retrieved from the X-ray archives at the University Hospital of North Norway between 1994 and 2010. At baseline, weight and height were measured, whereas information on the other covariates were obtained through self-reported questionnaires. Cox regression was used to estimate the hazard ratio (HR) of fracture in age- and gender-specific quintiles of grip-strength, and per 1 SD lower grip strength. Similar analyses were done solely for hip fractures. Adjustments were made for age, height, body mass index (BMI), marital status, education, smoking, physical activity, use of alcohol, self-perceived health, and self-reported diseases.

RESULTS

In 2891 men and 4002 women aged 50-79 years, 1099 non-vertebral osteoporotic fractures-including 393 hip fractures-were sustained during the median 15 years follow-up. Risk of non-vertebral osteoporotic fracture increased with declining grip strength: hazard ratios per SD decline was 1.22 (95% CI 1.05-1.43) in men and 1.09 (95% CI 1.01-1.18) in women. HR for fracture in lower vs. upper quintile was 1.58 (95% CI 1.02-2.45) in men and 1.28 (95% CI 1.03-1.59) in women. The association was most pronounced in men aged 50-64 years with HR = 3.39 (95% CI 1.76-6.53) in the lower compared to the upper quintile.

CONCLUSIONS

The risk of non-vertebral osteoporotic fracture increased with declining grip-strength in both genders, particularly in men aged 50-64 years.

The association between alcohol consumption and risk of hip fracture differs by age and gender in Cohort of Norway: a NOREPOS study

The association between alcohol consumption and hip fracture differed by gender: Men aged 30-59 years drinking frequently or 14+ gl/week had higher risk than moderate drinkers. No significant association was seen in older men. Women not drinking alcohol had higher risk than those drinking moderately both regarding frequency and amount.

INTRODUCTION

We aimed to examine alcohol consumption and risk of hip fracture according to age and gender in the population-based Cohort of Norway (1994-2003).

METHODS

Socio-demographics, lifestyle, and health were self-reported and weight and height were measured in 70,568 men and 71,357 women ≥ 30 years. Information on subsequent hip fractures was retrieved from hospitals' electronic patient registries during 1994-2013. Frequency of alcohol consumption was categorized: never/seldom, moderate (≤ 2-3 times/week), or frequent (≥ 4 times/week), and amount as number of glasses per week: 0, 1-6, 7-13, 14-27, and 28+. Type of alcohol (wine vs. beer/hard liquor) was also examined. Cox's proportional hazards regression was used to estimate hazard ratios (HRs) stratified on gender and baseline age < 60 and ≥ 60 years.

RESULTS

During median 15-year follow-up, 1558 men and 2511 women suffered a hip fracture. Using moderate drinkers as reference, men < 60 years drinking frequently had multivariable adjusted HR = 1.73 (CI 1.02-2.96) for hip fracture and more than 2.5 times higher risk if they consumed 14+ glasses compared to 1-6 glasses per week. In other groups of age and gender, no statistically significant increased risk was found in those consuming the highest levels of alcohol. Compared to women with moderate or frequent alcohol use, never/seldom-drinking women had the highest fracture risk. In women, use of wine was associated with lower fracture risk than other types of alcohol.

CONCLUSIONS

Risk of hip fracture was highest in men < 60 years with the highest frequency and amount of alcohol consumption and in non-drinking women.

Osteoporosis and osteopenia in the distal forearm predict all-cause mortality independent of grip strength: 22-year follow-up in the population-based Tromsø Study

Low bone mineral density (BMD) gives an increased risk of fractures, which can lead to premature death. Can BMD of the wrist predict mortality? BMD consistent with osteopenia and osteoporosis gave a significantly increased risk of death for both men and women in a general population in Tromsø, Norway.

INTRODUCTION

To investigate if bone mineral density (BMD) levels of the distal forearm, consistent with osteopenia and osteoporosis, can predict mortality and if grip strength is an effect modifier.

METHODS

The study population constituted 6565 participants aged 50-79 years at baseline in the Tromsø Study wave 4 conducted in 1994-1995. Forearm BMD measured by SXA was categorized as "normal," "osteopenia," or "osteoporosis" following WHO's definition. Cox regression with all-cause mortality as the outcome over 22 years of follow-up was performed for men and women separately, adjusting for health-related factors, as well as BMD by grip strength interaction. A secondary analysis with a 15-year follow-up also adjusted for hip fractures and osteoporotic fractures.

RESULTS

During follow-up, 3176 of participants died (47%). Those categorized as osteoporotic had higher mortality hazard ratio (HR) compared to those with normal BMD; men HR = 1.37 (95% confidence interval (CI) 1.19, 1.58) and women HR = 1.32 (1.14, 1.53) were adjusted for age, body mass index, physical activity, smoking habits, education, health status, chronic diseases, and grip strength. Corresponding HRs for osteopenia were men HR = 1.13 (1.00, 1.27) and women HR = 1.17 (1.01, 1.35). Further adjustments for fractures did only marginally attenuate the results, and HRs were still significant. There was no grip strength by BMD interaction.

CONCLUSION

Men and women with low distal forearm BMD values, consistent with osteoporosis or osteopenia, had an increased mortality compared to normal BMD participants. High grip strength did not modify this association, and the association remained after adjustment for a range of health-related factors.

Excess mortality following hip fracture: impact of self-perceived health, smoking, and body mass index. A NOREPOS study

Self-perceived health, smoking, and body mass index measured years before the hip fracture predicted excess post-hip fracture mortality, and even hip fracture patients with the most favorable levels of these risk factors had higher mortality than subjects who did not fracture.

INTRODUCTION

This study aimed to investigate the impact of pre-fracture self-perceived health, smoking, and body mass index (BMI) on excess post-hip fracture mortality using matched peers without hip fracture as reference.

METHODS

The study was based on the Cohort of Norway (CONOR) consisting of 10 regional health studies (1994-2003) and the NOREPOS hip fracture database (1994-2008). A matched cohort design was used to compare survival between hip fracture patients and subjects without fracture (matched on gender, age at participation in CONOR, and study site). Subjects aged ≥60 years were included. Hazard ratios were estimated using stratified Cox regression. Age-standardized mortality was also calculated.

RESULTS

Overall, hip fracture patients (N = 3177) had a 2.26-fold (95 % CI 2.13, 2.40) increased mortality compared to matched subjects (N = 20,282). The highest excess mortality was found in hip fracture patients reporting poor health (HR 4.08, 95 % CI 3.17, 5.26) and daily smoking (HR 3.25, 95 % CI 2.89, 3.66) and in patients with BMI <18.5 (HR 3.07, 95 % CI 2.11, 4.47) prior to the fracture. However, excess mortality was also observed in hip fracture patients in all other categories of BMI, self-perceived health, and smoking.

CONCLUSIONS

Information on self-perceived health, smoking, and BMI collected years before hip fracture predicted excess post-hip fracture mortality, and even hip fracture patients with the most favorable levels of these risk factors had higher mortality than the matched subjects who did not fracture. This suggests that both pre-fracture health status and factors related to the hip fracture itself might affect post-hip fracture mortality.

Continued decline in hip fracture incidence in Norway: a NOREPOS study

The previously reported decline in age-adjusted hip fracture rates in Norway during 1999-2008 continued after 2008. The annual number of hip fractures decreased in women and increased in men.

INTRODUCTION

Norway has among the highest hip fracture incidence rates ever reported despite previously observed declining rates from 1999 through 2008. The aim of the present study was to investigate whether this downward trend continued through 2013, and to compare gender-specific trends in 5 year age-groups during three time periods: 1999-2003, 2004-2008, and 2009-2013.

METHODS

All hip fractures (cervical, trochanteric, and sub-trochanteric) admitted to Norwegian hospitals were retrieved. Annual age-standardized incidence rates of hip fracture per 10,000 person-years by gender were calculated for the period 1999-2013. Time trends were tested by age-adjusted Poisson regression.

RESULTS

From 1999 through 2013 there were 140,136 hip fractures in persons aged 50 years and above. Age-adjusted hip fracture incidence rates declined by 20.4 % (95 % CI: 18.6-20.1) in women and 10.8 % (95 % CI: 7.8-13.8) in men, corresponding to an average annual age-adjusted decline of 1.5 % in women and 0.8 % in men. Except for the oldest men, hip fracture rates declined in all age-groups 70 years and older. The average annual number of fractures decreased in women (-0.3 %) and increased in men (+1.1 %).

CONCLUSIONS

During the past 15 years, hip fracture rates have declined in Norway. The forecasted growing number of older individuals might, however, cause an increase in the absolute number of fractures, with a substantial societal economic and public health burden.

25-Hydroxyvitamin D in pregnancy and genome wide cord blood DNA methylation in two pregnancy cohorts (MoBa and ALSPAC)

The aim of the study was to investigate whether maternal mid-pregnancy 25-hydroxyvitamin D concentrations are associated with cord blood DNA methylation. DNA methylation was assessed using the Illumina HumanMethylation450 BeadChip, and maternal plasma 25-hydroxyvitamin D was measured in 819 mothers/newborn pairs participating in the Norwegian Mother and Child Cohort (MoBa) and 597 mothers/newborn pairs participating in the Avon Longitudinal Study of Parents and Children (ALSPAC). Across 473,731CpG DNA methylation sites in cord blood DNA, none were strongly associated with maternal 25-hydroxyvitamin D after adjusting for multiple tests (false discovery rate (FDR)>0.5; 473,731 tests). A meta-analysis of the results from both cohorts, using the Fisher method for combining p-values, also did not strengthen findings (FDR>0.2). Further exploration of a set of CpG sites in the proximity of four a priori defined candidate genes (CYP24A1, CYP27B1, CYP27A1 and CYP2R1) did not result in any associations with FDR<0.05 (56 tests). In this large genome wide assessment of the potential influence of maternal vitamin D status on DNA methylation, we did not find any convincing associations in 1416 newborns. If true associations do exist, their identification might require much larger consortium studies, expanded genomic coverage, investigation of alternative cell types or measurements of 25-hydroxyvitamin D at different gestational time points.

A combination of low serum concentrations of vitamins K1 and D is associated with increased risk of hip fractures in elderly Norwegians: a NOREPOS study

The present study investigated the risk of incident hip fractures according to serum concentrations of vitamin K1 and 25-hydroxyvitamin D in elderly Norwegians during long-term follow-up. The results showed that the combination of low concentrations of both vitamin D and K1 provides a significant risk factor for hip fractures.

INTRODUCTION

This case-cohort study aims to investigate the associations between serum vitamin K1 and hip fracture and the possible effect of 25-hydroxyvitamin D (25(OH)D) on this association.

METHODS

The source cohort was 21,774 men and women aged 65 to 79 years who attended Norwegian community-based health studies during 1994-2001. Hip fractures were identified through hospital registers during median follow-up of 8.2 years. Vitamins were determined in serum obtained at baseline in all hip fracture cases (n = 1090) and in a randomly selected subcohort (n = 1318). Cox proportional hazards regression with quartiles of serum vitamin K1 as explanatory variable was performed. Analyses were further performed with the following four groups as explanatory variable: I: vitamin K1 ≥ 0.76 and 25(OH)D ≥ 50 nmol/l, II: vitamin K1 ≥ 0.76 and 25(OH)D < 50 nmol/l, III: vitamin K1 < 0.76 and 25(OH)D ≥ 50 nmol/l, and IV: vitamin K1 < 0.76 and 25(OH)D < 50 nmol/l.

RESULTS

Age- and sex-adjusted analyses revealed an inverse association between quartiles of vitamin K1 and the risk of hip fracture. Further, a 50 % higher risk of hip fracture was observed in subjects with both low vitamin K1 and 25(OH)D compared with subjects with high vitamin K1 and 25(OH)D (HR 1.50, 95 % CI 1.18-1.90). The association remained statistically significant after adjusting for body mass index, smoking, triglycerides, and serum α-tocopherol. No increased risk was observed in the groups low in one vitamin only.

CONCLUSION

Combination of low concentrations of vitamin K1 and 25(OH)D is associated with increased risk of hip fractures.

Abdominal obesity increases the risk of hip fracture. A population-based study of 43,000 women and men aged 60-79 years followed for 8 years. Cohort of Norway

BACKGROUND

The question as to whether abdominal obesity has an adverse effect on hip fracture remains unanswered. The purpose of this study was to investigate the associations of waist circumference, hip circumference, waist-hip ratio, and body mass index with incident hip fracture.

METHODS

The data in this prospective study is based on Cohort of Norway, a population-based cohort established during 1994-2003. Altogether 19,918 women and 23,061 men aged 60-79 years were followed for a median of 8.1 years. Height, weight, waist and hip circumference were measured at baseline using standard procedures. Information on covariates was collected by questionnaires. Hip fractures (n = 1,498 in women, n = 889 in men) were identified from electronic discharge registers from all general hospitals in Norway between 1994 and 2008.

RESULTS

The risk of hip fracture decreased with increasing body mass index, plateauing in obese men. However, higher waist circumference and higher waist-hip ratio were associated with an increased risk of hip fracture after adjustment for body mass index and other potential confounders. Women in the highest tertile of waist circumference had an 86% (95% CI: 51-129%) higher risk of hip fracture compared to the lowest, with a corresponding increased risk in men of 100% (95% CI 53-161%). Lower body mass index combined with abdominal obesity increased the risk of hip fracture considerably, particularly in men.

CONCLUSION

Abdominal obesity was associated with an increased risk of hip fracture when body mass index was taken into account. In view of the increasing prevalence of obesity and the number of older people suffering osteoporotic fractures in Western societies, our findings have important clinical and public health implications.

Low serum concentrations of alpha-tocopherol are associated with increased risk of hip fracture. A NOREPOS study

We investigated the risk of hip fracture according to circulating alpha-tocopherol, a plant-derived substance with antioxidant properties, in community-dwelling older Norwegians. We found a linear increasing risk of hip fracture with lower serum alpha-tocopherol concentrations, with a 51% higher risk in the lowest compared to the highest quartile.

INTRODUCTION

Oxidative stress is a suggested contributing cause of osteoporosis and fractures. Vitamin E (α-tocopherol) has potent antioxidant properties in humans. The relationship between circulating α-tocopherol and fracture risk is not established. The aim of this study was to investigate the association between serum α-tocopherol concentrations and risk of hip fracture during up to 11 years of follow-up.

METHODS

We performed a case-cohort analysis among 21,774 men and women aged 65-79 years who participated in four community-based health studies in Norway 1994-2001. Serum α-tocopherol concentrations at baseline were determined in 1,168 men and women who subsequently suffered hip fractures (median follow-up 8.2 years) and in a random sample (n = 1,434) from the same cohort. Cox proportional hazard regression adapted for gender-stratified case-cohort data was performed.

RESULTS

Median (25, 75 percentile) serum α-tocopherol was 30.0 (22.6, 38.3) μmol/L, and it showed a linear inverse association with hip fracture: hazard ratio (HR) 1.11 (95% confidence interval (CI) 1.04-1.20) per 10-μmol/L decrease in serum α-tocopherol, adjusted for gender and study center. The lowest compared to the highest quartile conferred an HR of 1.51 (95% CI 1.17-1.95), adjusted for gender and study center. Adjustment for smoking, month of blood sample, BMI, education, physical inactivity, self-rated health, and serum 25-hydroxyvitamin D (25(OH)D) yielded similar results. Taking serum total cholesterol concentration into account attenuated the association somewhat: HR of hip fracture was 1.37 (95% CI 1.05-1.77) in first versus fourth quartile of serum α-tocopherol/total cholesterol ratio.

CONCLUSIONS

Low serum concentrations of α-tocopherol were associated with increased risk of hip fracture in older Norwegians.

Procollagen type 1 amino-terminal propeptide (P1NP) and risk of hip fractures in elderly Norwegian men and women. A NOREPOS study

The current study aimed to assess a possible association between the bone turnover marker procollagen type 1 amino-terminal propeptide (P1NP) and future hip fractures in elderly Norwegian men and women and to elucidate the relation between P1NP, bone mineral density and 25-hydroxyvitamin D (25(OH)D). Men and women aged 71 to 77 from two population based health studies in Norway (1999-2001) were followed for a median period of 7.3 years with respect to hip fractures. The study was designed as a case-cohort study. P1NP and 25(OH)D were analysed in frozen serum samples obtained at baseline in hip fracture patients (n=340) and in randomly selected sex stratified sub-cohorts. Bone mineral density was measured by dual-energy X-ray absorptiometry (DXA) in a subset of participants. Cox proportional hazards regression with inverse probability weighting and robust variance was performed. No significant correlation between 25(OH)D and P1NP was found. A negative correlation between P1NP and BMD was observed in women (Rho=-0.36, p=0.001). A similar trend was observed in men. No association between quartiles of P1NP and rate of subsequent hip fractures was found. Spline analyses suggested a higher rate of hip fracture at P1NP levels above 60 μg/L in both men and women. A higher hip fracture rate, which was independent of BMD, was also indicated in women with very low levels of P1NP.

Prevalence and predictors of vitamin D deficiency in five immigrant groups living in Oslo, Norway: the Oslo Immigrant Health Study

OBJECTIVE

To study the prevalence of vitamin D deficiency and to identify possible predictors of vitamin D deficiency in five main immigrant groups in Oslo.

DESIGN

Cross-sectional, population-based.

SETTING

City of Oslo.

SUBJECTS

In total, 491 men and 509 women with native countries Turkey, Sri Lanka, Iran, Pakistan and Vietnam living in the county of Oslo.

RESULTS

Median serum 25(OH)D level (s-25(OH)D) was 28 nmol/l, ranging from 21 nmol/l in women born in Pakistan to 40 nmol/l in men born in Vietnam. Overall prevalence of vitamin D deficiency defined as s-25(OH)D<25 nmol/l was 37.2%, ranging from 8.5% in men born in Vietnam to 64.9% in women born in Pakistan. s-25(OH)D did not vary significantly with age. s-25(OH)D was higher in blood samples drawn in June compared to samples obtained in April, but not significantly for women. Reported use of fatty fish and cod liver oil supplements showed a strong positive association with s-25(OH)D in all groups. Education length was positively associated with s-25(OH)D in women, whereas body mass index (BMI) was inversely associated with s-25(OH)D in women. These two variables were not related to vitamin D deficiency in men.

CONCLUSIONS

There is widespread vitamin D deficiency in both men and women born in Turkey, Sri Lanka, Iran, Pakistan and Vietnam residing in Oslo. The prevalence of vitamin D deficiency is higher in women than in men, and it is higher in those born in Pakistan and lower in those born in Vietnam compared to the other ethnic groups. Fatty fish intake and cod liver oil supplements are important determinant factors of vitamin D status in the groups studied. BMI and education length are also important predictors in women.