Bone mineral density in adolescents. Higher values in a rural area--a population-based study of 246 subjects in southern Sweden

Molecular and cellular mechanisms linking air pollution and bone damage

Air pollution is the second most important risk factor associated with noncommunicable diseases after smoking. The effects of pollution on health are commonly attributable to particulate matter (PM), a complex mixture of particles suspended in the air. PM can penetrate the lower respiratory tract and has harmful direct and indirect effects on different organs and tissues. Direct effects are caused by the ability of PM components to cross the respiratory membrane and enter the bloodstream; indirect effects are systemic consequences of the local airway response. Recent work suggests that PM is an independent risk factor for low bone mineral density and osteoporosis-related fractures. Osteoporosis is a common age-related disease closely linked to bone fractures, with severe clinical consequences affecting quality of life, morbidity, and mortality. In this review, we discuss potential mechanisms behind the association between outdoor air pollution, especially PM, and bone damage. The discussion features four main mechanisms: 1) several different atmospheric pollutants can induce low-grade systemic inflammation, which affects bone metabolism through a specific effect of cytokines such as TNFα, IL-1β, IL-6, and IL-17 on osteoblast and osteoclast differentiation and function; 2) some pollutants, particularly certain gas and metal compounds, can cause oxidative damage in the airway and bone cells; 3) different groups of pollutants can act as endocrine disruptors when binding to the receptors in bone cells, changing their functioning; and 4) air pollution can directly and indirectly cause vitamin D deficiency. Characterizing these mechanisms will better define the physiopathology of bone damage, and recognizing air pollution as a modifiable risk factor for osteoporosis will inform environmental policies. Such knowledge will also guide the prevention of fractures due to fragility and help reduce health-related costs.

Bone mineral density in an urban and a rural children population-A comparative, population-based study in Enugu State, Nigeria

INTRODUCTION

Osteoporosis is one of the non-communicable diseases linked to urbanisation. The foundation of osteoporotic fractures stems from childhood. Therefore, studies that promote maximising peak bone mass are strongly advocated. Studies have shown that there are differences in the incidence of osteoporotic fractures in rural and urban communities. No study has investigated urban-rural differences in BMD of Nigerian children. This study, therefore, aimed to investigate urban-rural differences in BMD of Nigerian children and the association with physical activity, demographic and anthropometric variables.

METHODS

In a cross-sectional, study in Enugu, Nigeria, estimated bone mineral density (eBMD) was measured at the calcaneum using the QUS densitometer, Hologic Sahara, in 457 urban (Enugu metropolis) and 559 rural (Nsukka community) children aged 6-14 years. Height, weight and physical activity were measured. Independent sample t-test was used for comparative analysis while Pearson correlation coefficients and multiple regression models were used to examine the relationship between the eBMD and the other parameters.

RESULTS

The mean (S.D) eBMD of the urban children [0.52(0.09) g/cm²] were significantly higher (p < 0.05) than their age- and gender-matched counterparts in the rural areas [0.51(0.08) g/cm²]. Age and weight predicted (p < 0.05) the eBMD in the urban subjects while only age was the predictor (p < 0.05) in the rural subjects. The physical activity pattern had no relationship with eBMD in both urban and rural children in Enugu, Nigeria.

CONCLUSIONS

The eBMD of rural children is lower than that of their age- and gender-matched urban counterparts.

Rural older people had lower mortality after accidental falls than non-rural older people

Objective

This study aimed to investigate the mortality rate after falls of rural and non-rural older people and to explore the risk factors of mortality after falls among older people.

Patients and methods

This population-based case–control study identified two groups from a nationwide claim database (National Health Insurance Research Database in Taiwan): a rural group and a non-rural group, which included 3,897 and 5,541 older people, respectively, who were hospitalized for accidental falls (The International Classification of Diseases, Ninth Revision, Clinical Modification: E880–E888) during 2006–2009. Both groups were followed up for 4 years after falls. Four-year cumulative all-cause mortality rate after falls was calculated, and the demographic factor, comorbidity, and medications were considered as the potential risk factors of mortality after falls.

Results

The rural group had a significantly higher frequency of fall-related hospitalizations (7.4% vs 4.3%, P<0.001), but a lower 4-year cumulative all-cause mortality rate after falls than the non-rural group (8.8% vs 23.4%, P<0.001). After adjusting for age, gender, comorbidity, and medication use, the rural group had a significantly lower risk of mortality after falls than the non-rural group (adjusted odds ratio =0.32, 95% confidence interval =0.28–0.37, P<0.001). Age, gender, place of residence, comorbidity, number of medications, and inappropriate medication use were independent risk factors of mortality after falls.

Conclusion

The rural older people had a higher frequency of fall-related hospitalizations but lower mortality after falls than the non-rural older people. Fall prevention programs should be adjusted for difference in place of residence.

Rural-Urban Differences of Dietary Patterns, Overweight, and Bone Mineral Status in Chinese Students

China is an urban and rural social model country. In the past three decades, the developing speed of rural areas has been much slower than urban areas, which may lead to the differences in dietary patterns. This study aimed to investigate the disparities of dietary structures from urban and rural children, and to analyze the effects of different dietary patterns on their adverse outcome. Among 1590 students, aged 11 years to 17 years, from primary and middle schools, a cross-sectional study was conducted. There were three dietary patterns recognized: Westernization structure, meat diet structure, and Western and Chinese structure. Compared with rural students, more urban students were in the highest categories of the whole dietary patterns (p < 0.001). Overweight/obesity and central adiposity were more prevailing among urban students, while rural students had a more prevailing risk of bone fracture (p < 0.05). Through the adjustment for all confounding factors, the Westernization structure could increase the risk of overweight/obesity and central adiposity, the meat structure could increase the risk of elevated blood pressure/hypertension, while the risk of low bone mineral quality could be reduced by the Chinese and Western structure. In conclusion, a rural-urban disparity in dietary patterns was found in our study, and different dietary patterns were associated with the risk of some adverse outcomes. Therefore, there were different prevalences of the adverse outcomes between rural and urban students.

Rural vs. non-rural differences and longitudinal bone changes by DXA and pQCT in men aged 20-66 years: A population-based study

The purpose of this research was to determine whether there were differences in estimated means and rates of change in BMC, bone area, BMD and measures of bone geometry among men (n=544) from three distinct populations (Hutterite [rural], rural non-Hutterite, non-rural), and whether activity levels or calcium intake explain these population differences. Men were enrolled in the South Dakota Rural Bone Health Study and followed for 7.5 years to estimate means and rates of change in bone mass, density, size and geometry. Femoral neck (FN) and spine measurements were obtained every 18 months by DXA and distal radius (4% and 20%) measurements by pQCT. Activity measurements and calcium intake were obtained quarterly for the first 3 years and at 54, 72, and 90 months. Rural men had greater percent time in moderate plus vigorous activity (mean ± SD: 22 ± 10 vs. 15 ± 8%, p<0.001) and greater lean mass (69 ± 9 vs. 66 ± 10 kg, p=0.05) than non-rural men. Both rural populations (Hutterite and rural men) had larger femoral neck (FN) bone area and greater 20% radius cross-sectional area than non-rural men ([least square means ± SE] FN area: 5.90 ± 0.02 and 5.86 ± 0.02 vs. 5.76 ± 0.03 cm(2), p<0.001 and p=0.03 respectively and cross-sectional area: 171.0 ±1.3 and 165.5 ± 1.5 vs. 150.3 ± 1.6mm(2), both p<0.001). Despite lower cortical vBMD in Hutterite and rural men compared to non-rural men (1182 ± 2 and 1187 ± 2 vs. 1192 ± 2 mm(2), p<0.001 and p=0.06 respectively), bone strength (pSSI) was greater (429 ± 5 and 422 ± 5 vs. 376 ± 6 mm(3), both p<0.001). The rates of change in femoral neck BMC and aBMD and trabecular vBMD also differed by rural lifestyle, with greater losses among non-rural men in their 20s and 60s compared to both Hutterite and rural populations (time-by-age-by-group interactions, both p<0.01). Physical activity was not found to be a potential mediator of population differences. Baseline calcium intake was associated with FN aBMD (p=0.04), and increases in calcium intake were associated with spine BMC (p=0.04) and inversely associated with cortical area (p=0.02). There was some evidence for mediation by either baseline calcium intake or changes in calcium intake over the study period, but the influence on population differences were negligible. We speculate that rural-non-rural differences in bone occur earlier in life or are a result of factors that have not yet been identified.

Comparison of Bone Mineral Density between Urban and Rural Areas: Systematic Review and Meta-Analysis

BACKGROUND

Studies from high income countries (HIC) have generally shown higher osteoporotic fracture rates in urban areas than rural areas. Low bone mineral density (BMD) increases susceptibility to fractures. This review aimed to assess whether urbanicity is consistently associated with lower BMD globally.

METHOD

Ovid MEDLINE, EMBASE, and Global Health (-April 2013) were searched for articles investigating differences in bone mineral content (BMC) or BMD between urban and rural areas. Ratio of means (RoM) of BMD were used to estimate effect sizes in meta-analysis, with an exception for one study that only presented BMC data.

RESULTS

Fifteen articles from eleven distinct populations were included in the review; seven populations from four high income countries and four from three low and middle income countries (LMIC). Meta-analysis showed conflicting evidence for urban-rural difference in BMD; studies from high income countries generally showed higher BMD in rural areas while the results were more mixed in studies from low and middle income countries (HIC RoM = 0.05; 95% CI: 0.03 to 0.06; LMIC RoM = -0.04: 95% CI: -0.1 to 0.01).

CONCLUSIONS

Urban-rural differences of bone mineral density may be context-specific. BMD may be higher in urban areas in some lower income countries. More studies with robust designs and analytical techniques are needed to understand mechanisms underlying the effects of urbanization on bone mass accrual and loss.

Life-course determinants of bone mass in young adults from a transitional rural community in India: the Andhra Pradesh Children and Parents Study (APCAPS)

BACKGROUND

Undernutrition and physical inactivity are both associated with lower bone mass.

OBJECTIVE

This study aimed to investigate the combined effects of early-life undernutrition and urbanized lifestyles in later life on bone mass accrual in young adults from a rural community in India that is undergoing rapid socioeconomic development.

DESIGN

This was a prospective cohort study of participants of the Hyderabad Nutrition Trial (1987-1990), which offered balanced protein-calorie supplementation to pregnant women and preschool children younger than 6 y in the intervention villages. The 2009-2010 follow-up study collected data on current anthropometric measures, bone mineral density (BMD) measured by dual-energy X-ray absorptiometry, blood samples, diet, physical activity, and living standards of the trial participants (n = 1446, aged 18-23 y).

RESULTS

Participants were generally lean and had low BMD [mean hip BMD: 0.83 (women), 0.95 (men) g/cm²; lumbar spine: 0.86 (women), 0.93 (men) g/cm²]. In models adjusted for current risk factors, no strong evidence of a positive association was found between BMD and early-life supplementation. On the other hand, current lean mass and weight-bearing physical activity were positively associated with BMD. No strong evidence of an association was found between BMD and current serum 25-hydroxyvitamin D or dietary intake of calcium, protein, or calories.

CONCLUSIONS

Current lean mass and weight-bearing physical activity were more important determinants of bone mass than was early-life undernutrition in this population. In transitional rural communities from low-income countries, promotion of physical activity may help to mitigate any potential adverse effects of early nutritional disadvantage.

Bone mineral density and incidence of hip fracture in Swedish urban and rural women 1987-2002

BACKGROUND AND PURPOSE

Although the incidence of hip fracture during the past 50 years has increased, a break in this trend has been reported in the last decade. Whether this change is attributable to changes in bone mineral density (BMD) or whether it varies between urban and rural regions is unknown.

METHODS

We evaluated changes in annual hip fracture incidence in women aged > or = 50 years in one urban population (n = 51,757) and one rural population (n = 26,446) from 1987 to 2002. We also examined secular differences in BMD (mg/cm(2)), evaluated by single-photon absorptiometry at the distal radius, prevalence of osteoporosis, and several other risk factors for hip fracture in one population-based sample of urban women and one sample of rural women aged 50-80 years at two time points: 1988/89 (n = 257 and n = 180, respectively) and 1998/99 (n = 171 and n = 118, respectively).

RESULTS

No statistically significant changes were evident in annual age-adjusted hip fracture incidence per 10(4) when analyzing all women (-0.01 per year (95% CI: -0.37, 0.35)), rural women (-0.38 per year (-1.05, 0.28)), or urban women (0.19 per year (-0.28, 0.67)). BMD (expressed as T-score) was similar in 1988/99 and 1998/99 when analyzing all women (-0.09 (-0.26, 0.09)), urban women (-0.04 (-0.27, 0.19)), or rural women (-0.15 (-0.42, 0.13)) women.

INTERPRETATION

Since no changes in age-adjusted hip fracture incidence and no differences in BMD were found during the study period, changes evident in the other risk factors for hip fracture that we investigated (such as gait velocity and balance) are either of minor importance or are counteracted by changes in other risk factors.

Daily physical education in the school curriculum in prepubertal girls during 1 year is followed by an increase in bone mineral accrual and bone width--data from the prospective controlled Malmö pediatric osteoporosis prevention study

The aim of this study was to evaluate a general school-based 1-year exercise intervention program in a population-based cohort of girls at Tanner stage I. Fifty-three girls aged 7-9 years were included. The school curriculum-based exercise intervention program included 40 minutes/school day. Fifty healthy age-matched girls assigned to the general school curriculum of 60 minutes physical activity/week served as controls. Bone mineral content (BMC, g) and areal bone mineral density (aBMD, g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body (TB), lumbar spine (L2-L4 vertebrae), third lumbar vertebra (L3), femoral neck (FN), and leg. Volumetric bone mineral density (g/cm(3)) and bone width were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the TB scan. No differences at baseline were found in age, anthropometrics, or bone parameters when the groups were compared. The annual gain in BMC was 4.7 percentage points higher in the lumbar spine and 9.5 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in aBMD was 2.8 percentage points higher in the lumbar spine and 3.1 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in bone width was 2.9 percentage points higher in L3 in cases than in controls (P < 0.001). A general school-based exercise program in girls aged 7-9 years enhances the accrual of BMC and aBMD and increases bone width.

Contribution of lean tissue mass to the urban-rural difference in bone mineral density

While the urban-rural difference in bone mineral density (BMD) has been shown in some, but not all, Western populations, such a difference and the reason for the difference is largely unknown, particularly in developing countries. This cross-sectional, epidemiologic study was designed to examine the hypothesis that differences in measures of body composition such as lean mass (LM) and fat mass (FM) contribute to the urban-rural difference in BMD. Lean mass, fat mass, lumbar spine and femoral neck BMD were measured by DXA (GE Lunar Corp, Wis.) in 411 urban (Bangkok city) and 436 rural (Khon Kaen province) Thai subjects, aged 20-84 years. Rural men and women had significantly higher LM and lower FM than their urban counterparts. In multiple linear regression analysis, age, LM, menopausal status (in women) and residence were independent determinants of BMD. After adjusting for age, menopause and LM, rural subjects were found to have significantly higher femoral neck BMD, but not lumbar spine BMD, than urban subjects. Furthermore, to alleviate the potential effect of multicolinearity of LM and FM, each rural subject was matched with each urban subject for FM and age, which resulted in 46 pairs of men and 91 pairs of women. In this matched-pair analysis, the femoral necks in rural men and women were, respectively, 7.3+/-2.1% (mean+/-SE; P<0.01) and 6.3+/-2.8% (P<0.02) higher than in urban men and women. The urban-rural difference in LM accounted for approximately 23 and 5% of the urban-rural difference in femoral neck BMD in men and women, respectively. These data are thus consistent with the hypothesis that the urban-rural difference in BMD at a weight-bearing site is in part associated with the urban-rural difference in lean mass.

Forearm bone mineral density in an unselected population of 2,779 men and women--the HUNT Study, Norway

The fracture incidence in Norway is among the highest in Europe, presumably due to osteoporosis. As part of a multipurpose health study in the county of Nord-Trondelag, Norway (the HUNT study), a 5% randomly selected sample (n=4,646) of the population >19 years of age was invited to undergo single X-ray absorptiometry (SXA) of the forearm. A total of 1,274 men (50.5 years) and 1,505 women (49.9 years) participated (60%). The aim of the study was to describe the variation in bone mineral density (BMD) and the prevalence of forearm BMD 2.5 standard deviations (SD) below the mean value for young adults in an unselected population sample. In women the BMD remained stable until the age of 50 years, whereupon a strong decline in BMD was observed. In men, a BMD increase was observed until about the age of 40 years; the decline after the age of 65 was, however, similar to that in women. Based on age and gender-specific reference values, the age-adjusted prevalence of T-scores <-2.5 SD in women and men aged 50-69 years was 16.0% and 5.6%, respectively. In the age group of 70 years or older the prevalence was 65.8% and 30.6% for women and men, respectively. The accelerated BMD reduction in women aged 50-65 explains the higher prevalence of T-score <-2.5 SD in elderly women than in men. Further studies on bone loss and falls are required to explain the high fracture incidence in Norway.

Effect of urbanization on bone mineral density: a Thai epidemiological study

Background

The incidence of fractures in rural populations is lower than in urban populations, although the reason for this difference is unclear. This cross-sectional study was designed to examine the difference in bone mineral density (BMD), a primary predictor of fracture risk, between urban and rural Thai populations.

Methods

Femoral neck and lumbar spine BMD was measured by dual-energy X-ray absorptiometry (GE Lunar, Madison, WI) in 411 urban and 436 rural subjects (340 men and 507 women), aged between 20 and 84 years. Body mass index (BMI) was calculated from weight and height.

Results

After adjusting for age and body weight in an analysis of covariance model, femoral neck BMD in rural men and women was significantly higher than those in urban men and women (P < 0.001), but the difference was not observed at the lumbar spine. After stratifying by sex, age group, and BMI category, the urban-rural difference in femoral neck BMD became more pronounced in men and women aged <50 years and with BMI ≥ 25 kg/m².

Conclusions

These data suggest that femoral neck BMD in rural men and women was higher than their counterparts in urban areas. This difference could potentially explain part of the urban-rural difference in fracture incidence.