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.

Plasma choline, nicotine exposure, and risk of low bone mineral density and hip fracture: the Hordaland health study.

Choline, obtained from diet and formed by biosynthesis, is the immediate precursor of betaine. Animal studies suggest an impact of choline on bone metabolism. We examined the associations of plasma choline and betaine with bone mineral density (BMD), the risk of hip fractures, and possible effect-modification by nicotine exposure. The Hordaland Health Study (1998 to 2000) included 7074 women and men (ages 46 to 49 or 71 to 74 years). In 5315, BMD was measured. The oldest (n = 3311) were followed for hip fractures through 2009. Risk associations were studied by logistic and Cox regression by comparing the lowest and middle tertiles with the highest, as well as trends across tertiles of plasma choline and betaine. In analyses adjusted for sex and age, participants in the lowest (odds ratio [OR] = 2.00, 95% confidence interval [CI] 1.69-2.37) and middle (OR = 1.39, CI 1.17-1.66) tertiles of plasma choline had an increased risk of low BMD (lowest quintile) (p trend < 0.001). Separate analyses for sex and age groups revealed the strongest relations in elderly women (lowest tertile: OR = 2.84, CI 1.95-4.14; middle tertile: OR = 1.80, CI 1.22-2.67, p trend < 0.001), and highest OR among those in the lowest tertile who were exposed to nicotine (OR = 4.56, CI 1.87-11.11). Low plasma choline was also associated with an increased risk of hip fracture in elderly women and men (lowest tertile: hazard ratio [HR] = 1.45, CI 1.08-1.94; middle tertile: HR = 1.13, CI 0.83-1.54, p trend = 0.012). In elderly women, the HR for hip fracture was 1.90 (CI 1.32-2.73) and 1.36 (CI 0.92-1.99) (p trend < 0.001) for lowest and middle tertiles of choline, and the highest HR was found among women in the lowest tertile exposed to nicotine (HR = 2.68, CI 1.16-6.19). Plasma betaine was not related to BMD or hip fracture. Low plasma choline was associated with low BMD in both sexes and increased the risk of hip fracture in elderly women. These results should motivate further studies on choline, nicotine exposure, and bone metabolism.

Vitamin D inadequacy is associated with low-energy distal radius fractures: a case-control study.

INTRODUCTION: Vitamin D inadequacy is associated with hip fractures, but the relationship has not been explored for distal radius fractures. AIMS: To compare serum 25-hydroxyvitamin D (s-25(OH)D) status in low-energy distal radius fracture patients and a group of matched controls, and examine whether observed differences in s-25(OH)D between patients and controls would remain after adjusting for bone mineral density (BMD), body mass index (BMI), and smoking history. METHODS: A total of 575 female and 72 male low-energy distal radius fracture patients (50-90 years) and 534 female and 52 male matched controls were included. The primary measure was levels of vitamin D. Secondary measures were BMD assessed by dual energy X-ray absorptiometry, BMI and smoking history. RESULTS: Mean s-25(OH)D was 66.5nmol/L in female patients and 78.7nmol/L in controls (p<0.001). The corresponding figures in men were 64.5 and 77.0nmol/L (p=0.017). In adjusted conditional logistic regression analyzes, s-25(OH)D <50nmol/L (OR=2.32, 95% CI: 1.47-3.64, p<0.001), and 50-75 (OR=1.70, 95% CI: 1.17-2.47, p=0.005) were associated with distal radius fractures in women. s-25(OH)D <50nmol/L (OR=6.27, 95% CI: 1.17-33.66, p=0.032) was associated with distal radius fractures in men. CONCLUSIONS: Vitamin D inadequacy is associated with low-energy distal radius fractures in both women and men. Differences in vitamin D levels are independent of BMD, BMI or smoking history.