Effect of antiepileptic medication on bone mineral measures.

OBJECTIVE: Long-term antiepileptic drug (AED) use has been associated with bone disease, but many previous studies have been limited by inadequate control subjects. We used a cotwin affected sib-pair model to investigate this issue. METHODS: The authors studied 31 female twin (15 monozygous and 16 dizygous) and four sibling pairs (< 3 years age difference) aged 21 to 75 years, in which one member had > 12 months of AED treatment. Areal bone mineral density (ABMD, g/cm2) was measured at the lumbar spine (LS), total hip (TH), femoral neck (FN), and total forearm (FA). Three primary a priori defined subgroups were analyzed: a) use for > 2 years, b) use of enzyme-inducing AEDs, or c) age older than 40 years. RESULTS: For all pairs (n = 35), there were no significant within-pair differences in any ABMD measure. However, in Subgroup a (n = 27), there was a within-pair difference at the FA (0.513 vs 0.534, -3.9%, p = 0.016). In Subgroup b (n = 29), there was also a within-pair difference at the FA for AED user vs nonuser (0.508 vs 0.529, -3.8%, p = 0.010). In Subgroup c (n = 15), there were within-pair differences at the FA (0.492 vs 0.524, -6.1%, p = 0.017) and the LS (0.884 vs 0.980, -9.8%, p = 0.036). CONCLUSIONS: Patients using AEDs for > 2 years, in particular those taking enzyme-inducing AEDs and those older than 40 years, have significantly lower bone mineral density at clinically relevant fracture risk sites.

Determinants of bone density in 30- to 65-year-old women: a co-twin study.

UNLABELLED: Reported effects of body composition and lifestyle on bone mineral density in pre-elderly adult women have been inconsistent. In a co-twin study, we measured bone mineral density, lean and fat mass, and lifestyle factors. Analyzing within pair differences, we found negative associations between bone mineral density and tobacco use (2.3-3.3% per 10 pack-years) and positive associations with sporting activity and lean and fat mass. INTRODUCTION: Reported effects of body composition and lifestyle of bone mineral density in pre-elderly adult women have been inconsistent. METHODS: In a co-twin study of 146 female twin pairs aged 30 to 65 years, DXA was used to measure bone mineral density at the lumbar spine, total hip, and forearm, total body bone mineral content, and lean and fat mass. Height and weight were measured. Menopausal status, dietary calcium intake, physical activity, current tobacco use, and alcohol consumption were determined by questionnaire. Within-pair differences in bone measures were regressed through the origin against within-pair differences in putative determinants. RESULTS: Lean mass and fat mass were associated with greater bone mass at all sites. A discordance of 10 pack-years smoking was related to a 2.3-3.3% (SE, 0.8-1.0) decrease in bone density at all sites except the forearm, with the effects more evident in postmenopausal women. In all women, a 0.8% (SE, 0.3) difference in hip bone mineral density was associated with each hour per week difference in sporting activity, with effects more evident in premenopausal women. Daily dietary calcium intake was related to total body bone mineral content and forearm bone mineral density (1.4 +/- 0.7% increase for every 1000 mg). Lifetime alcohol consumption and walking were not consistently related to bone mass. CONCLUSION: Several lifestyle and dietary factors, in particular tobacco use, were related to bone mineral density. Effect sizes varied by site. Characterization of determinants of bone mineral density in midlife and thereafter may lead to interventions that could minimize postmenopausal bone loss and reduce osteoporotic fracture risk.

Relationships with serum parathyroid hormone in old institutionalized subjects.

OBJECTIVE AND BACKGROUND: Old people in residential care are at the highest risk of any group for hip fracture. This may relate to their high prevalence of hyperparathyroidism. There are few data, however, on relationships with serum parathyroid hormone (PTH) in these individuals. This study therefore examined complex associations with serum PTH in nursing home and hostel residents. DESIGN: Cross-sectional analysis. PATIENTS: One hundred and forty-three nursing home and hostel residents of median age 84 years. MEASUREMENTS: Serum PTH, 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D (1,25-(OH)2D), plasma creatinine, phosphate, calcium, albumin, Bsm-1 vitamin D receptor genotype, age, weight and use of frusemide or thiazide. RESULTS: The statistical models determined accounted for half the interindividual variation in serum PTH. Heavier weight was associated with both the prevalence of secondary hyperparathyroidism and the serum concentration of PTH. Novel interactions with serum PTH were identified between: weight and 25OHD; 25OHD and phosphate; and phosphate and thiazide diuretic use. Plasma phosphate was associated with PTH independently of calcium and 1,25-(OH)2D. There was no independent association between PTH and nuclear vitamin D receptor genotype. CONCLUSIONS: Heavier weight is associated with both the prevalence and severity of secondary hyperparathyroidism and consistent with animal models of secondary hyperparathyroidism, phosphate may relate to serum PTH independently of 1,25-(OH)2D or calcium.

Association of birth weight and current body size to blood pressure in female twins.

It has been proposed that low birth weight is associated with high levels of blood pressure in later life. The aim of this study was to assess the relationship of blood pressure to birth weight and current body size during growth and adulthood. A total of 711 female multiple births, with one group of 244 in their growth phase mean age 12.0 (2.3)(SD) years and the other of 467 adults (mean age 35.2 (12.6) years), had height, weight and both systolic (SBP) and diastolic (DBP) blood pressures measured, and self-reported their birth weight. Regression analyses were performed to assess the cross-sectional and within-pair associations of blood pressure to birth weight, with and without adjustments for current body size. Within-pair analysis was based on 296 twin pairs. Cross-sectionally, a reduction in birth weight of 1 kg was associated with 2 to 3 mm Hg higher age-adjusted SBP, which was of marginal significance and explained about 2% of the population variance. Adjustment for body mass index did not significantly change this association. Within-pair analyses found no association between birth weight and SBP or DBP,even after adjusting for current body size. After age, current body size was the strongest predictor of systolic BP. The weak association of blood pressure to birth weight cross-sectionally is of interest, but any within-pair effect of birth weight on blood pressure must be minimal compared with the effect of current body size.