The risk of all-cause mortality is inversely related to serum 25(OH)D levels.

CONTEXT AND OBJECTIVES: Vitamin D plays a key role in maintaining bone health, but evidence for its nonskeletal effects is inconsistent. This study aims to examine the association between serum 25-hydroxyvitamin D [25(OH)D] levels and all-cause mortality in a large general population cohort. DESIGN, PARTICIPANTS, AND SETTING: Using the computerized database of the largest health care provider in Israel, we identified a cohort of subjects 20 years old or older with serum 25(OH)D levels measured between January 2008 and December 2009. Vital status was ascertained through August 2011. RESULTS: Median follow-up was 28.5 months (interquartile range 23.8-33.5 months); 7,247 of 182,152 participants (4.0%) died. Subjects who died had significantly lower serum 25(OH)D levels (mean 44.8 ± 24.2 nmol/liter) than those alive at the end of follow-up (51.0 ± 23.2 nmol/liter), P < 0.001. After adjustment for age, gender, ethnicity, and seasonality, the hazard ratio (HR) for all-cause mortality was 2.02 [95% confidence interval (CI) 1.89-2.15] for the lowest serum 25(OH)D quartile (<33.8 nmol/liter) compared with the highest. After further adjustment for comorbidity, use of vitamin D supplements and statins, smoking, socioeconomic status, and body mass index, the HR was 1.81 (95% CI 1.69-1.95). This remained, even after adjustment for serum low-density lipoprotein, high-density lipoprotein, calcium level (corrected for serum albumin levels), and glomerular filtration rate, 1.85 (95% CI 1.70-2.01). The fully adjusted HR associated with being in the second 25(OH)D quartile (33.8-49.4 nmol/liter) was 1.25 (95% CI 1.16-1.34). CONCLUSIONS: All-cause mortality is independently and inversely associated with serum 25(OH)D levels at levels less than 50 nmol/liter.

The longitudinal variability of serum 25(OH)D levels.

BACKGROUND: The extent to which a single serum 25(OH)D measurement represents long-term vitamin D status remains unclear. This study aims to assess the variability of serum 25(OH)D between tests taken at different time intervals. METHODS: Using the computerized database of the largest healthcare provider in Israel, we identified subjects in whom a serum 25(OH)D test was performed on at least two different occasions between January 2008 and September 2011 (n = 188,771). For these subjects we selected the first and the last dated tests, then we identified those who were not treated with supplements during the last 6 months before the first and before the last test (n = 94,418). Of these we analyzed subjects in whom the first and the last tests were performed in the same month of the year (n = 8881). RESULTS: The mean serum 25(OH)D level at the first test was 51.7 ± 24.0 nmol/L and was 56.7 ± 24.7 at the last test (P<0.001); the overall correlation was 0.63 (P < 0.001). For vitamin D status in two categories (<50 versus ≥ 50 nmol/L), the percentage of agreement between the first and last tests was 74.4%, and was 50.8% for vitamin D status in four categories (<30, 30-49.9, 50-74.9, and ≥ 75 nmol/L). The correlation decreased with increasing time between the tests ranging from 0.83 for tests done at the same year to 0.55 after 3 years. The more the first levels were higher or lower, the more likely subjects remain in their first category (≥ 50 versus <50 nmol/L). CONCLUSIONS: Long-term month specific serum 25(OH)D levels are relatively stable.

Vitamin D Status in Israeli subjects before the initiation and after the cessation of vitamin D supplements.

Vitamin D supplements are often recommended to restore sufficiency, although the adherence to treatment is low. This study assessed vitamin D status at different time intervals following the cessation of treatment. The database of Clalit-Health-Services (CHS), a not-for-profit HMO covering more than half of the Israeli population, was retrospectively searched for all members with available serum 25OHD test results in 2009 (245,493). We then identified those who filled any cholecalciferol prescription in 2008-2009 (121,817). Subjects were included in the final analysis only if they started treatment in 2009, had serum 25OHD < 50 nmol/l before the first prescription in 2009, and had at least one additional test result after the last dated prescription in 2009 (5,461). Serum 25OHD increased from 32 ± 11 nmol/l at baseline to 58.6 ± 22.3 nmol/l after treatment (P < 0.001). The proportion of subjects with sufficient vitamin D after treatment increased with increasing cholecalciferol daily dose and treatment duration (P < 0.001) and decreased with increasing time from cessation of treatment (P < 0.001). The effect of time from treatment cessation persisted after controlling for baseline serum 25OHD, daily cholecalciferol dose, treatment duration, seasonality, gender, age, ethnicity, and BMI; the ORs for sufficient vitamin D were 2.02 (95% CI 1.66-2.45), 1.67 (1.39-2.01), and 1.23 (1.04-1.47) for >30-60, 61-99, and 100-155 days compared to >155 days, respectively. Long-term vitamin D treatment is needed to maintain sufficient levels in those with baseline serum 25OHD below 50 nmol/l.