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Vitamin D and bone health: Epidemiologic studies.

ABSTRACT: Allelic variation in the vitamin D receptor was the first non-structural gene to be associated with osteoporosis, and together with the effects of the vitamin D system on bone homeostasis, suggested that this vitamin might have a strong role in bone health. However, controversy exists regarding what level of serum 25-hydroxyvitamin D (25(OH)D) is optimal. Current data from biochemical, observational and randomized controlled trials (RCTs), indicate serum 25(OH)D levels of at least 50 nmol l(-1) are required for normalization of parathyroid hormone (PTH) levels, to minimize the risk of osteomalacia and for optimal bone cell function. The skeletal consequences of 25(OH)D insufficiency include secondary hyperparathyroidism, increased bone turnover and bone loss and an increased risk of minimal trauma fractures. In large scale epidemiological studies, serum 25(OH)D levels are associated with bone mineral density in both men and women. However, there is mixed evidence on the effectiveness of optimizing serum 25(OH)D levels for the prevention of bone loss and minimal trauma fractures in postmenopausal women and older men. There may be some benefit on primary fracture prevention for those who have inadequate serum levels of 25(OH)D, particularly in institutionalised elderly patients, but only when combined with calcium supplements. For optimal bone health, evidence from RCTs suggests vitamin D may be considered a threshold nutrient with few further bone benefits observed at levels of 25(OH)D above which PTH is normalized. An adequate calcium intake is also imperative to gain optimum benefit from an improved vitamin D status in those with insufficient 25(OH)D levels, with an increased calcium intake being associated with suppression of PTH levels.

SUBMITTER: Ebeling PR

PROVIDER: S-EPMC4015454 | biostudies-other | 2014

REPOSITORIES: biostudies-other

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Project description:BackgroundStudies have suggested that agreement between administrative health data and self-report for asthma status ranges from fair to good, but few studies benefited from administrative health data over a long period. We aimed to (1) evaluate agreement between asthma status ascertained in administrative health data covering a period of 30 years and from self-report, and (2) identify determinants of agreement between the two sources.MethodsWe used administrative health data (1983-2012) from the Quebec Birth Cohort on Immunity and Health, which included 81,496 individuals born in the province of Quebec, Canada, in 1974. Additional information, including self-reported asthma, was collected by telephone interview with 1643 participants in 2012. By design, half of them had childhood asthma based on health services utilization. Results were weighted according to the inverse of the sampling probabilities. Five algorithms were applied to administrative health data (having ≥ 2 physician claims over a 1-, 2-, 3-, 5-, or 30-year interval or ≥ 1 hospitalization), to enable comparisons with previous studies. We estimated the proportion of overall agreement and Kappa, between asthma status derived from algorithms and self-reports. We used logistic regression to identify factors associated with agreement.ResultsApplying the five algorithms, the prevalence of asthma ranged from 49 to 55% among the 1643 participants. At interview (mean age = 37 years), 49% and 47% of participants respectively reported ever having asthma and asthma diagnosed by a physician. Proportions of agreement between administrative health data and self-report ranged from 88 to 91%, with Kappas ranging from 0.57 (95% CI: 0.52-0.63) to 0.67 (95% CI: 0.62-0.72); the highest values were obtained with the [≥ 2 physician claims over a 30-year interval or ≥ 1 hospitalization] algorithm. Having sought health services for allergic diseases other than asthma was related to lower agreement (Odds ratio = 0.41; 95% CI: 0.25-0.65 comparing ≥ 1 health services to none).ConclusionsThese findings indicate good agreement between asthma status defined from administrative health data and self-report. Agreement was higher than previously observed, which may be due to the 30-year lookback window in administrative data. Our findings support using both administrative health data and self-report in population-based epidemiological studies.

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Vitamin D and bone health: Epidemiologic studies.

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