Page 140 - Vitamin D and Cancer

6 Vitamin D: Cardiovascular Function and Disease 127

The fourth study, from Germany on patients (n = 3,258) referred for coronary
angiography and followed for a median period of 7.7 years, is described here
because it had a similar design as the above studies [138]. Patients with baseline
serum 25OHD levels in the bottom quartile had a significantly increased relative
risk of all-cause mortality (hazard ratio = 2.08; 95% CI: 1.60, 2.70) and CV mortal-
ity (hazard ratio = 2.22; 95% CI: 1.57, 3.13) compared with those in the highest
baseline 25OHD quartile, after adjusting for the full range of covariates, including
baseline serum 1,25(OH) D which also was independently and inversely associated
2
with follow-up risk of all-cause and CV mortality.
The study designs used in the first three of these studies provide the best-quality
evidence to date on the association between vitamin D status and risk of CV disease
in the general population [135–137], aside from the Women’s Health Initiative
randomized control trial of vitamin D supplementation which has methodological
weaknesses (see Sect. 6.4.3) [139].
Consistent with the above cohort studies, a 2006 case–control study from
Cambridge (UK) found that mean Z score of 25OHD for incident stroke cases,
measured within 30 days of disease onset, was significantly below that expected for
a sample of healthy controls (−1.4, 95% CI: −1.7, −1.1; p < 0.0001) [140]. In
contrast, a hospital-based case–control study of coronary artery disease from India
reported in 2001 that a significantly (p < 0.001) higher proportion of cases (59.4%)
than controls (22.1%) had serum 25OHD levels above 222.5 nmol/L [141]. A limi-
tation of this study is that it recruited prevalent cases of coronary artery disease, an
unknown time after their heart attacks, when their vitamin D status may not have
reflected that at the time of disease onset.
Further studies have been published on vitamin D and congestive heart failure.
A case control study from Germany found significantly lower serum 25OHD and
1,25(OH) D levels in cases and controls [142], while low serum 1,25(OH) D (but
2
2
not 25OHD) predicted increased risk of death or need for heart transplant in
patients with end-stage congestive heart failure [143]. In contrast, a recent German
randomized controlled trial of 93 patients with congestive heart failure failed to
show an effect of vitamin D supplementation on measures of cardiac function with
echocardiography [144]. Information has recently been reported on vitamin D and
arterial disease. Analyses of NHANES data (for 2001–2004) found that the preva-
lence ratio of peripheral arterial disease increased by 1.35 (95% CI: 1.15, 1.59) for
each 10 ng/mL (25 nmol/L) decrease in serum 25OHD [145].

6.4.2.2 Blood Pressure

This decade has also seen the publication of large epidemiological studies of vita-
min D and blood pressure. A large cross-sectional study from Norway (n = 15,596)
found that dietary vitamin D was unrelated to blood pressure [146]. Results from
three large US health professional cohorts (total n = 209,313) did not show an asso-
ciation between dietary vitamin D and incident hypertension [147]; although a
recent US study of female health professionals (n = 28,886) reported that risk of