Dose-related effect of urinary cotinine levels on bone mineral density among Korean females

Association of secondhand smoke with fracture risk in community-dwelling nonsmoking adults in Korea

Although the detrimental effects of active smoking on bone health have been widely recognized, the impact of secondhand smoke exposure on fracture risk in non-smokers remains less understood. A total of 4843 nonsmokers aged 40-69 yr, who participated in the Korean Genome and Epidemiology Study from 2001 to 2018, were analyzed. The participants were categorized into two groups based on their exposure status to secondhand smoke: currently exposed and unexposed. The exposure group was subsequently divided into two subgroups based on the median weekly exposure time (high vs low). The incidence of new fractures was determined using self-reported questionnaires. The identified fractures were categorized according to the fracture site: overall, vertebral, hip, non-vertebral, and non-vertebral non-hip fractures. The mean age of the participants was 52.4 yr (84.1% women). Exposure to secondhand smoke was associated with an increased risk of fracture (adjusted hazard ratio [aHR]: 1.27, P = 0.028) after adjusting for multiple covariates including age, sex, BMI, household income, bone density of mid-shaft tibia, C-reactive protein, alcohol consumption, and fracture history. Secondhand smoke remained as a significant risk factor for fracture, independent of the major osteoporotic fracture probabilities estimated using a fracture risk assessment tool (aHR: 1.24, P = 0.038). The high exposure group had higher risk of fracture than that of the unexposed group (aHR: 1.33, P = 0.025), whereas the fracture risk did not differ significantly between low exposure and unexposed groups (aHR: 1.18, P = 0.253), suggesting a potential dose-response relationship. Secondhand smoke showed robust association with increased risk of non-vertebral (aHR: 1.37, P = 0.008) or non-vertebral non-hip fractures (aHR: 1.36, P = 0.013), while its association with vertebral fracture was attenuated (aHR: 1.03, P = 0.908). Secondhand smoke was associated with an elevated risk of fracture in nonsmokers, independent of clinical risk factors.

Association between blood cadmium levels and the risk of osteopenia and osteoporosis in Korean post-menopausal women

We aimed to investigate the association between cadmium levels and the risk of osteopenia and osteoporosis in Korean post-menopausal women. There was a significant positive association between cadmium levels and the risk of osteopenia and osteoporosis, but further studies for dose response are required.

PURPOSE

Cadmium exposure can exert detrimental effects on bone health, particularly in post-menopausal women. However, previous studies have failed to report an association in Korean post-menopausal women. We aimed to investigate the association between cadmium levels and the risk of osteopenia and osteoporosis in Korean post-menopausal women.

METHODS

In total, 5432 participants from the 4th and 5th Korean National Health and Nutrition Examination Survey (KNHANES) were randomly sampled for measurements of heavy metal concentrations in the blood, bone mass density (BMD), and nutrient intake. We analyzed data for 1031 post-menopausal women ≥50 years of age. Blood cadmium levels were categorized into quartiles, and a multinomial logistic regression model was used for analysis.

RESULTS

There was a significant positive association between cadmium levels and the risk of osteopenia and osteoporosis, but the odds ratio (OR) at the 4th level was lower than that at the 3rd level (OR and 95% confidence interval (CI) for osteopenia: 2nd quartile: 1.24, 0.88-1.74; 3rd quartile: 3.22, 2.24-4.64; 4th quartile: 1.27, 0.87-1.85; P for trend <0.001; OR and 95% CI for osteoporosis: 2nd quartile: 1.54, 1.05-2.25; 3rd quartile: 3.63, 2.31-5.69; 4th quartile: 1.70, 1.03-2.81; P for trend <0.001). This trend was consistent in the sensitivity analysis.

CONCLUSION

Our findings suggest that there is an association between blood cadmium levels and the risk of osteopenia and osteoporosis in Korean post-menopausal women. However, further prospective studies are required to determine whether there is a dose-response relationship and address potential selection bias, especially in patients with femoral neck osteoporosis.

Smoking cessation increases levels of osteocalcin and uncarboxylated osteocalcin in human sera

Smoking is thought to be a risk factor for osteoporosis development; however, the consequences of stopping smoking for bone homeostasis remain unknown. Here we conducted two separate human studies and show that bone mineral density was significantly lower in smokers than in non-smokers. The first was an observational study of pre- and post-menopausal healthy female smokers and non-smokers; the second included 139 current smokers determined to stop smoking. In the second study, levels of bone formation markers such as osteocalcin and uncarboxylated osteocalcin significantly increased after successful smoking cessation, as verified by significantly reduced levels of serum cotinine, a nicotine metabolite. Moreover, nicotine administration to mice reduced bone mineral density and significantly increased the number of osteoclasts in bone. Reduced bone mass phenotypes seen in nicotine-treated mice were significantly increased following nicotine withdrawal, an outcome accompanied by significantly reduced serum levels of tartrate-resistant acid phosphatase, a bone resorption marker. Taken together, our findings suggest that bone homeostasis is perturbed but can be rescued by smoking cessation.

Differential association of dietary fat intake with DXA-based estimates of bone strength according to sex in the KNHANES IV population

The higher the dietary fat intake is in men, the worse their bone strength. By contrast, in women, both low and high fat intakes have negative impacts on bone strength. Dietary fat intake may be a modifiable factor affecting bone health, but this needs to be reconfirmed in further studies.

PURPOSE

Despite the general belief that higher fat intake may be harmful for bone health, its impact on bone strength has not been thoroughly studied.

METHODS

We conducted a population-based cross-sectional study derived from the Korea National Health and Nutrition Examination Surveys, including 2590 participants. Composite indices of femoral neck strength, such as the compression strength index (CSI), bending strength index (BSI), and impact strength index (ISI), were generated by combining bone mineral density, weight, and height with the femoral axis length and width. Nutritional status was assessed using a 24-h dietary recall questionnaire.

RESULTS

Dietary fat intake (%: energy from fat intake/total energy intake × 100) was inversely related to CSI and ISI in men, but not in women. Men in the highest three fat intake quintiles had lower CSI, BSI, and/or ISI than those in the lowest quintile (P = 0.003-0.041). In women, compared with participants in the third fat intake quintile, those in the other four quintiles had lower CSI, BSI, and/or ISI (P = 0.004-0.049). When participants were allocated to three groups according to the dietary reference intake of fat in Koreans [low (< 15%), moderate (15-30%), or high (≥ 30%)], men with a moderate or high fat intake had significantly lower ISIs than those with a low fat intake (P = 0.045 and 0.040, respectively). By contrast, compared with women consuming a moderate amount of fat, those with a high intake had lower CSI, BSI, and ISI (P = 0.024-0.048).

CONCLUSION

Higher fat intake in men may contribute to deteriorations in bone strength. However, this finding and the observed sex differences need to be reconfirmed using established methods for assessment of dietary intake other than the 24-h dietary recall method employed in this study.

Fixed night workers and failed smoking cessation

Background

The objective of this study was to examine the relationship between employee work schedule and failure in smoking cessation.

Methods

Logistic regression was used to estimate the association between work schedule and failed smoking cessation rate among 4927 male workers who had attempted smoking cessation. The data was obtained from the annual Korean National Health and Nutrition Examination Survey from 2007 to 2015 (excluding data from 2013). An adjusted model, including demographic and occupational variables, was constructed after stratifying the data into two subgroups by age (the 19- to 40-year-old group and the 41- to 60-year-old group).

Results

The percentage of smoking-cessation failure varied according to work schedule and age. The failure rate in the 19- to 40-year-old group was generally higher for all work schedule categories than in the 41- to 60-year-old group. In particular, the highest percentage (90.9%) of smoking-cessation failure was in the fixed overnight work group. After adjusting for demographic characteristics and work organization variables, the odds ratio for failed smoking cessation across all ages was 3.30 (95%CI 2.23–4.86) among the fixed overnight workers compared to the daytime workers. Both of the age-stratified subgroups maintained this relationship, with a notably higher OR in the 19- to 40-year-old group (OR 3.74, 95% CI 1.80–7.77).

Conclusions

Fixed overnight work is likely to negatively affect smoking cessation compared to other work schedules. Tailored anti-smoking intervention programs are required based on work schedule.

Impact of smoking on thyroid gland: dose-related effect of urinary cotinine levels on thyroid function and thyroid autoimmunity

Cigarette smoking is believed to affect thyroid function and autoimmune thyroid disease. However, there is little information to analyze their association using objective biomarkers. The aim of this study was to investigate the dose-related effect of smoking on thyroid hormones and thyroid peroxidase antibody (TPO Ab) using urinary cotinine levels and a population-based cohort. The present study used the thyroid hormone and urinary cotinine dataset from sixth Korean National Health and Nutrition Examination Survey in 2014 and 2015, and a total of 4249 participants were included. Dose-response relationships between thyroid hormone (free T4, TSH, and TPO Ab) and urinary cotinine levels were estimated using ANCOVA after adjustment for all variables (age, height, weight, alcohol, exercise, and log- transformed iodine in urine). Urinary cotinine level was negatively correlated with TSH. The estimated coefficients were −0.0711 in males and −0.0941 in females (p < 0.0001). TPO Ab titer was positively correlated with cotinine levels in males (p < 0.0001). Our findings indicated a significant dose-related effect of urinary cotinine level on thyroid function, and thyroid autoimmunity.

The Effect of Tobacco Smoking on Musculoskeletal Health: A Systematic Review

This systematic review explored associations between smoking and health outcomes involving the musculoskeletal system. AMSTAR criteria were followed. A comprehensive search of PubMed, Web of Science, and Science Direct returned 243 articles meeting inclusion criteria. A majority of studies found smoking has negative effects on the musculoskeletal system. In research on bones, smoking was associated with lower BMD, increased fracture risk, periodontitis, alveolar bone loss, and dental implant failure. In research on joints, smoking was associated with increased joint disease activity, poor functional outcomes, and poor therapeutic response. There was also evidence of adverse effects on muscles, tendons, cartilage, and ligaments. There were few studies on the musculoskeletal health outcomes of secondhand smoke, smoking cessation, or other modes of smoking, such as waterpipes or electronic cigarettes. This review found evidence that suggests tobacco smoking has negative effects on the health outcomes of the musculoskeletal system. There is a need for further research to understand mechanisms of action for the effects of smoking on the musculoskeletal system and to increase awareness of healthcare providers and community members of the adverse effects of smoking on the musculoskeletal system.

The positive association of total protein intake with femoral neck strength (KNHANES IV)

Data gathered from a nationally representative cohort demonstrate that higher dietary protein intake was positively associated with the composite indices of femoral neck strength in both men and women, suggesting that higher protein intake may contribute to lower risk of hip fracture through the improvement of bone strength.

INTRODUCTION

Despite the general belief that higher protein intake may be helpful for bone homeostasis, its impact on human bone health is still debated. Furthermore, the association of dietary protein intake with femoral neck (FN) strength, which can predict fracture risk independently of bone mineral density (BMD), has not been thoroughly studied.

METHODS

This is a population-based, cross-sectional study from Korea National Health and Nutrition Examination Surveys, including 592 men aged 50 years or older and 590 postmenopausal women. The composite indices of FN strength, such as the compression strength index (CSI), bending strength index (BSI), and impact strength index (ISI), were generated by combining BMD, body weight, and height with the femoral axis length and width, which were measured by dual-energy X-ray absorptiometry.

RESULTS

After adjustment for confounders, total protein intake (g/kg/day) positively correlated with all three FN composite indices in both genders (P = 0.006 to 0.035), except for BSI showing marginal significance in postmenopausal women (P = 0.093). Consistently, compared with subjects in lowest total protein intake quartile, those in the highest quartile showed markedly higher CSI, BSI, and ISI values (P = 0.043 to < 0.001), with a dose-response manner across increasing total protein intake quartile categories in both men and women (P for trend = 0.028 to < 0.001).

CONCLUSIONS

These findings provide the clinical evidence that higher dietary protein intake can play a beneficial role on bone health through the increase of FN strength relative to load in adults.

Smoking and bone mineral density: comprehensive analyses of the third National Health and Nutrition Examination Survey (NHANES III)

Some questions remain on the relationship between smoking and bone health. Detailed analyses of the relationship between smoking and BMD are presented, essentially ruling out non-linear associations as an explanation for inconsistent results in the literature.

INTRODUCTION

To provide comprehensive multiple regression and dose-response analyses of the association between smoking behavior variables and bone health as assessed by radiologically determined bone mineral density in NHANES III.

METHODS

Analyzes of a representative cross-sectional survey of the noninstitutionalized population of the USA. Self-reported smoking behavior and bone mineral density of 14,510 participants were analyzed using survey design-based multiple linear regression modeling. Dose-response patterns were analyzed using restricted cubic spline regression.

RESULTS

Femoral neck bone mineral density in current smokers was numerically lower than in never smokers, but this was not statistically significant after controlling for confounders. In former smokers, bone mineral density T scores were 0.064 units higher for every 10 years of abstinence, with little impact of confounder adjustment. Spline regression revealed no relevant non-linearity in the associations studied.

CONCLUSIONS

Non-linearity is an unlikely explanation for inconsistent results in the literature on smoking and bone mineral density. Further and especially longitudinal studies of the complex relationship smoking with bone health would be particularly important given the still substantial prevalence of smoking in an aging global population.

Effect of Secondhand Smoking, Determined by Urinary Cotinine Level on Bone Health

Background:

We evaluated the relationship between secondhand smoke (SHS) inhalation, as verified by urinary cotinine levels, and bone health.

Methods:

We analyzed the nationwide, population-based, cross-sectional health survey. We included 1936 men aged 50 years or older who checked bone mineral density (BMD) from the Korean National Health and Nutrition Examination Survey (2008–2010). Current smokers assessed by urinary cotinine levels higher than 500 ng/mL were excluded (n = 616). Exposure to SHS was determined using a 50 ng/mL urinary cotinine threshold.

Results:

The estimated prevalence of SHS exposure in our cohort was 13.9%. After adjusting for age and body mass index (BMI), T-scores at total femur (P < 0.001), femoral neck (P < 0.001), and lumbar spine (P = 0.004) were lower in SHS exposure versus nonexposure groups. Impaired bone health (osteopenia or osteoporosis) at femoral neck or lumbar spine was evident in 61.7% and 48.6% of SHS exposure and nonexposure cases, respectively (P = 0.004). Moreover, after adjusting for age, BMI, and health habits, the odds ratio for impaired bone health in the SHS exposure group was 1.89 (95% confidence interval: 1.31–2.74).

Conclusions:

Our findings suggest that SHS exposure, determined by urinary cotinine levels, is negatively associated with BMD and is a leading cause of impaired bone health in Korean men.

Amount of smoking, pulmonary function, and bone mineral density in middle-aged Korean men: KNHANES 2008-2011

Smoking induces bone loss; however, data on the relationship between smoking history and bone mineral density (BMD) are lacking. Age and pulmonary function can affect BMD. We investigated the relationships among pack-years (PYs) of smoking, pulmonary function, and BMD in middle-aged Korean men (50-64 years old). This cross-sectional study used data from the Korean National Health and Nutrition Examination Survey, 2008-2011. All participants underwent BMD measurements using dual energy X-ray absorptiometry and pulmonary function tests using standardized spirometry. In total, 388 never-smokers and 1088 ever-smokers were analyzed. The number of PYs of smoking was negatively correlated with total hip BMD (r = -0.088; P = 0.004) after adjusting for age, height, and weight. Ever-smokers were classified into 3 groups according to PYs of smoking. The highest tertile (n = 482) exhibited significantly lower total hip bone mass than the lowest tertile (n = 214) after adjusting for confounding factors (age, height, weight, forced expiratory volume in 1 s (FEV₁), alcohol consumption, physical activity, and vitamin D levels) that could affect bone metabolism (P = 0.003). In conclusion, smoking for >30 PYs was significantly associated with low hip BMD after adjusting for pulmonary function in middle-aged Korean men. Long-term smoking may be a risk factor for bone loss in middle-aged men independent of age, height, weight, and pulmonary function.

The relationship between fatty liver index and bone mineral density in Koreans: KNHANES 2010-2011

Analyses using a nationally representative cohort have revealed that high fatty liver index (FLI) is associated with low bone mineral density (BMD) regardless of insulin resistance in men, thereby supporting the deteriorated bone metabolism in nonalcoholic fatty liver disease (NAFLD).

INTRODUCTION

NAFLD is linked to deteriorated bone health. We investigated the association of FLI, a scoring model for NAFLD, with BMD.

METHODS

This was a population-based, cross-sectional study from the Korea National Health and Nutrition Examination Surveys including 4264 Koreans (1908 men and 2356 women). FLI was calculated using body mass index, waist circumference, serum triglyceride, and gamma-glutamyltranspeptidase level. Insulin resistance was evaluated using the homeostasis model assessment-estimated insulin resistance (HOMA-IR) index. BMD was measured using dual-energy X-ray absorptiometry at the lumbar spine, total hip, femoral neck, and whole body.

RESULTS

Men had a higher FLI than women, while the HOMA-IR index was similar between men and women. The significant association between FLI and BMD was observed only in men, but not in women. FLI was negatively correlated with total hip, femoral neck, and whole body BMD in men after adjusting for all potential confounders, including HOMA-IR (P < 0.001 to 0.010). Lumbar spine, total hip, femoral neck, and whole body BMD in men showed a decreasing trend as the FLI tertile increased after adjusting for all potential confounders, including HOMA-IR (P for trends < 0.001 to 0.034). In men aged 50 years or older, odds ratios for combined osteopenia and osteoporosis increased across increasing FLI tertiles after adjusting for confounders (P for trends < 0.011 to 0.029).

CONCLUSION

NAFLD is associated with low bone density regardless of insulin resistance in men. These findings suggest an undiscovered direct link between liver and bone that increases the risk of osteoporosis in men with NAFLD.

Effectiveness of government anti-smoking policy on non-smoking youth in Korea: a 4-year trend analysis of national survey data

OBJECTIVES

Since the Health Promotion Act was introduced in Korea in 1995, anti-smoking policies and regulations have undergone numerous revisions, and non-smoking areas have gradually been expanded. The purpose of this study was to examine the impact of a partial legislative ban on adolescent exposure to secondhand smoke using objective urinary cotinine levels in a nationwide representative sample.

METHODS

Urine cotinine levels were measured in the Korea National Health and Nutrition Examination Survey from 2008 to 2011. This study was a trend analysis of 4 years of national survey data from 2197 Korean youth aged 10-18 years. Among non-smokers, the 75th percentile urinary cotinine level was estimated. We also considered the number of household smokers.

RESULTS

The 75th percentile urine cotinine level of non-smokers showed a significant decreasing trend from 2008 to 2011, from 15.47 to 5.37 ng/mL, respectively. Urine cotinine did not decline significantly in non-smokers living with smokers during the study period. The results did not show a statistically significant reduction in smoking rate in adolescents from 2008 to 2011, although there was a trend towards a decrease (p=0.081).

CONCLUSIONS

Based on urine cotinine levels, government-initiated anti-smoking policies have only been effective among highly exposed non-smoking adolescents during the study period. Further study needs to evaluate whether or not the legislative ban affects domestic smoking exposure.

Association between obesity and femoral neck strength according to age, sex, and fat distribution

Indicators of total and abdominal obesity were negatively associated with femoral neck strength indices. There are age-, sex-, and fat distribution-specific differences in the magnitude of these associations. These suggested that indicators of obesity with different magnitude according to age, sex, and fat distribution associated with poor bone health.

INTRODUCTION

Fat regulates bone metabolism, but the associations of total and abdominal obesity with bone health are inconsistent. We investigated the association between indicators of obesity and composite indices of femoral neck (FN) strength reflecting the risk of hip fracture.

METHODS

This population-based cross-sectional study examined data from the Korea National Health and Nutrition Examination Surveys. Participants were divided into groups according to age (25-49/≥50 years) and sex. We examined total fat mass (TFM) and percentage fat mass (pFM) as indicators of total obesity and truncal fat mass (TrFM) as an indicator of abdominal obesity. We calculated the composite indices of FN strength and anthropometric clinical indicators of abdominal obesity.

RESULTS

TFM, pFM, and TrFM were negatively associated with the composite indices, irrespective of age and sex (P < 0.001-0.005). Most anthropometric clinical indicators of abdominal obesity showed negative associations with the composite indices regardless of age and sex (P < 0.001-0.048), except for women aged 25-49 years. In men, magnitudes of the negative contributions of TFM to the composite indices were significantly stronger at age 25-49 years than at age ≥50 years. Magnitudes of negative associations of TFM with the composite indices were greater in men than in women. TrFM had a more detrimental effect than TFM on FN strength in men aged 25-49 years and in women of both ages.

CONCLUSION

Indicators of total and abdominal obesity negatively associated with FN strength, and magnitudes of their effects on bone health differed according to age, sex, and fat distribution.

Bone mineral density among Korean females aged 20-50 years: influence of age at menarche (The Korea National Health and Nutrition Examination Survey 2008-2011)

To evaluate a possible correlation between bone mineral density (BMD) and age at menarche, the present study used the BMD dataset of the Korea National Health and Nutrition Examination Survey IV-V (KNHANES IV-V). Age at menarche had a small but significant association with BMD of the lumbar spine in premenopausal Korean females, aged 20-50 years.

INTRODUCTION

To investigate any correlation between bone mineral density (BMD) and age at menarche in Korean females using data from the fourth and fifth Korea National Health and Nutrition Examination Survey (KNHANES IV-V; 2008-2011).

METHODS

In total, 37,753 individuals participated in health examination surveys between 2008 and 2011. A total of 5032 premenopausal females aged 20-50 years were eligible. Age, height, weight, and age at menarche were assessed.

RESULTS

Results from the univariate linear regression and analysis of covariance (ANCOVA) indicated that age (per 1 year), height (per 1 cm), weight (per 1 kg), exercise (per 1 day/week), familial osteoporosis history (yes), parity (n = 0 to ≥4), and menarche age distribution were associated with BMD of the total femur, femur neck, and lumbar spine. After stratifying the bone area and adjusting for age, parity, alcohol intake, smoking, exercise, and familial osteoporosis history, no effect was seen for the total femur or femur neck. Age at menarche 16~17 and ≥18 years groups were associated with BMD of the lumbar spine only.

CONCLUSIONS

Age at menarche had a small but significant association with BMD of the lumbar spine in premenopausal Korean females, aged 20-50 years. Females with late menarche may achieve lower peak bone mass at some skeletal sites, which may put them at greater risk for osteoporosis in later life.

Relationship between Heavy Metal Exposure and Bone Mineral Density in Korean Adult

Background

Exposure to heavy metals from environmental and industrial sources remains a concern of serious public health risk. This study was conducted to analysis the relationship between heavy metal concentrations and bone density.

Methods

This study used data from a nation-based sample of Koreans (n=2,429) from 2008 to 2011 Korea National Health and Nutrition Examination Survey. We were obtained heavy metals (lead, mercury and cadmium), socioeconomic and demographic factors and bone mineral density (BMD) measured by T-score.

Results

Menopausal women, current smoker or the frequent alcohol drinking, low educational level and low family income were greater in the osteopenia or osteoporosis groups than normal group, and were associated with an increased blood heavy metal concentration levels. The highest quartile group in blood lead had a 1.47 times (95% confidence interval [CI] 1.16-1.87) risk of osteopenia or osteoporosis. In case of blood cadmium, the risk for osteopenia or osteoporosis increased 2.1 times (95% CI 1.64-2.68).

Conclusions

We observed a significant association between blood heavy metals (lead and cadmium) levels and low BMD. Our findings suggest that heavy metal exposure may be a risk factor for osteoporosis.

Insulin resistance and composite indices of femoral neck strength in Asians: the fourth Korea National Health and Nutrition Examination Survey (KNHANES IV)

OBJECTIVE

Fracture risk in type 2 diabetes mellitus with insulin resistance is increased, despite relatively preserved bone mineral density (BMD). In this study, we investigated the relationship between insulin resistance and composite indices of femoral neck strength in Koreans.

DESIGN

A population-based, cross-sectional study from the Korea National Health and Nutrition Examination Survey PARTICIPANTS: About 1243 men and 1433 women MEASUREMENTS: Insulin resistance was evaluated using the homoeostasis model assessment-estimated insulin resistance (HOMA-IR) index. Femoral neck width and axis length were measured from hip dual-energy X-ray absorptiometry scans and combined with BMD, weight and height to calculate composite indices of femoral neck strength relative to load: compression (CSI), bending (BSI) and impact strength indices (ISI).

RESULTS

HOMA-IR showed an inverse relationship with CSI, BSI and ISI in both genders before and after adjusting for confounders (P < 0·001-0·029). CSI was more strongly associated with HOMA-IR than BSI and/or ISI in both genders (P < 0·001-0·013). When men were stratified according to HOMA-IR quartiles, all strength indices decreased as the quartile increased, after adjusting for all potential confounders (P for trend <0·001-0·001), whereas CSI and ISI did in women (P for trend = 0·012 and 0·002, respectively). Fasting insulin levels, but not glucose levels, were negatively associated with all strength indices regardless of confounders (P < 0·001-0·044).

CONCLUSIONS

Insulin resistance is associated with low femoral neck strength, particularly against the compressive load. These findings suggest a better approach to evaluate bone health in insulin-resistant individuals.

Gender differences in cadmium and cotinine levels in prepubertal children

Susceptibility to environmental stressors has been described for fetal and early childhood development. However, the possible susceptibility of the prepubertal period, characterized by the orchestration of the organism towards sexual maturation and adulthood has been poorly investigated and exposure data are scarce. In the current study levels of cadmium (Cd), cotinine and creatinine in urine were analyzed in a subsample 216 children from 12 European countries within the DEMOCOPHES project. The children were divided into six age-sex groups: boys (6-8 years, 9-10 years and 11 years old), and girls (6-7 years, 8-9 years, 10-11 years). The number of subjects per group was between 23 and 53. The cut off values were set at 0.1 µg/L for Cd, and 0.8 µg/L for cotinine defined according to the highest limit of quantification. The levels of Cd and cotinine were adjusted for creatinine level. In the total subsample group, the median level of Cd was 0.180 µg/L (range 0.10-0.69 µg/L), and for cotinine the median wet weight value was 1.50 µg/L (range 0.80-39.91 µg/L). There was no significant difference in creatinine and cotinine levels between genders and age groups. There was a significant correlation between levels of cadmium and creatinine in all children of both genders. This shows that even at such low levels the possible effect of cadmium on kidney function was present and measurable. An increase in Cd levels was evident with age. Cadmium levels were significantly different between 6-7 year old girls, 11 year old boys and 10-11 year old girls. As there was a balanced distribution in the number of subjects from countries included in the study, bias due to data clustering was not probable. The impact of low Cd levels on kidney function and gender differences in Cd levels needs further investigation.

Smoking and body fat mass in relation to bone mineral density and hip fracture: the Hordaland Health Study

Lower bone mineral density (BMD) in smokers may be attributable to lower body weight or fat mass, rather than to a direct effect of smoking. We analyzed the effects of smoking exposure, assessed by plasma cotinine, and body fat on BMD and the risk of subsequent hip fracture. In the community-based Hordaland Health Study (HUSK), 3003 participants 46-49 years and 2091 subjects 71-74 years were included. Cotinine was measured in plasma and information on health behaviors was obtained from self-administered questionnaires. BMD and total body soft tissue composition were measured by dual X-ray absorptiometry. Information on hip fracture was obtained from computerized records containing discharge diagnoses for hospitalizations between baseline examinations 1997-2000 through December 31st, 2009. In the whole cohort, moderate and heavy smokers had stronger positive associations between fat mass and BMD compared to never smokers (differences in regression coefficient (95% CI) per % change in fat mass = 1.38 (0.24, 2.52) and 1.29 (0.17, 2.4), respectively). In moderate and heavy smokers there was a nonlinear association between BMD and fat mass with a stronger positive association at low compared to high levels of fat mass (Davies segmented test, p<0.001). In elderly women and men, heavy smokers had an increased risk of hip fracture compared to never smokers (hazard ratio = 3.31, 95% CI: 2.05, 5.35; p<0.001). In heavy smokers there was a tendency of a lower risk of hip fracture with higher percentage of fat mass. The deleterious effect of smoking on bone health is stronger in lean smokers than in smokers with high fat mass.