To investigate the prevalence, self-awareness, and treatment of hypertension in Lhasa, Tibet, a total of 1370 native Tibetan aged ≥18 years were selected, using stratified proportional sampling. The study showed that the prevalence of hypertension was 51.2%, significantly higher in men (56.0%) than in women (48.0%) (P = .004). The hypertension prevalence increased with increasing age (77.8% in 60-74 y and 82.5% in ≥75 y groups) and was higher in urban, suburban, or agricultural area than in pastoral area (P < .001). The self-awareness, treatment, and control rate of hypertension were 63.5%, 24.3% and 7.7%, respectively. In multivariable regression analysis, age, urban residence, amount of daily intake of fat and oil, and body mass index <18.5 kg/m(2) were independently associated with hypertension. In conclusion, hypertension was highly prevalent among native Tibetan people in Lhasa, and the rates of self-awareness, treatment, and control of hypertension were low.
Our aim was to clarify whether substitution of cytosine for adenine at position 1166 (A1166C) polymorphism of the angiotensin II type 1 receptor (AT1R) gene is associated with susceptibility to essential hypertension in Han, Tibetan and Yi populations in China. This study involved 302 normotensive and 446 hypertensive subjects. The polymorphism was detected by polymelase chain reaction of genomic DNA and restriction fragment length polymorphism (PCR-RFLP) in genomic DNA. The data were analyzed by analysis of covariance (ANCOVA), X2 test, and multiple logistic regression. In normotensive controls, the A1166 allele frequencies were 0.979, 0.939 and 0.965 in Han, Tibetan and Yi participants, respectively. There was no significant intergroup variation in frequency of the allele in normotensives (X2=4.166, p=0.125). The frequency of the A1166 allele was significantly higher in Tibetan male hypertensives than that in normotensives (X2=11.46, p=0.001). There was no significant difference in A1166C genotype distribution and allele frequency between normotensives and hypertensives either in the Han (p=0.465) or Yi (p=0.357) populations. Body mass index in the Han and Yi populations (p=0.0001), age in the Tibetan and Yi populations (p=0.0001), and AA genotype in the Tibetan male population (p=0.0034) all were independent risk factors for hypertension. Diastolic blood pressure levels were significantly higher in Tibetan male subjects with the AA genotype than in those with the AC+CC genotype (p=0.0040). We concluded that the A1166 allele is very common in Han, Tibetan and Yi populations, approximately 1.35-fold more common than in Caucasians. The A1166 allele of the AT1R gene may be a predisposing factor for essential hypertension in Tibetan males. A1166C polymorphism of the AT1R gene is probably not involved in the pathogenesis of essential hypertension in Han or Yi populations.
UVB from the sun and intake from food are the only human sources of vitamin D. Tibet is a unique region for comparisons of these sources: (1) it lies at a low latitude and at a high altitude and has very large annual fluences of UVB; (2) the traditional Tibetan food is poor in vitamin D. Blood samples were taken from 63 persons of different age, with different occupations and staying at different places. UVB doses at these places were measured. The samples were analyzed by a standard radioimmune assay for determination of the serum concentration of 25 hydroxyvitamin D (25(OH)D). The main finding was that among nomads, there seems to be severe vitamin D deficiency (serum levels of 25(OH)D<30 nM). We tentatively propose that the low level of 25(OH)D of nomads is related to their clothing and sun exposure habits. For persons of other occupations (students, teachers and farmers) the levels are higher, although a significant fraction of these persons also have lower levels than 75 nm, by many regarded as a limit for insufficiency related to a number of negative health conditions. The annual dose of vitamin D-generating UVB is about five times larger in Lhasa than in Oslo. Despite this, the average vitamin D status seems to be similar, except in the case of nomads. This phenomenon is certainly related to food habits. In conclusion, the 25(OH)D status among nomads in Tibet appears to be alarmingly low. However, for people of other occupations the status is more normal.
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