Introduction

In the Chinese population, the prevalence of H-type hypertension was found to be 26.9% in the total population, including 81.8% of men and 62.8% of women, and 73.1% in patients with hypertension [1]. Hyperhomocysteinemia may be a potential independent risk factor for cardiovascular disease, dementia, and other related disorders [2], and a degree of synergy between hypertension and hyperhomocysteinemia can lead to an increased burden on the cardiovascular system. This suggests that the coexistence of hypertension and hyperhomocysteinemia may exacerbate the overall risk and impact of these conditions on individuals’ health. Studies have estimated that the incidence of adverse cardiovascular events in patients with H-type hypertension is approximately five times higher than in patients with essential hypertension alone and approximately 25–30 times higher than in the healthy population [3] 0.5,10-methylenetetrahydrofolate reductase (MTHFR) plays an important role as a key enzyme in folate metabolism and plasma Hcy remethylation in the body, and the C677T (rs1801133) locus gene of MTHFR is the most common one that can lead to reduced or diminished activity of the MTHFR enzyme and subsequent elevation of blood Hcy levels [4, 1). The higher the total score, the greater the risk of develo** H-type hypertension.

Fig. 1
figure 1

Nomogram for predicting the probability of H-type hypertension

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By calculating the C-index of this model (equivalent to the AUC under the ROC curve) as 0.808 (95% CI: 0.788–0.828), it suggests that the model exhibits a relatively strong discriminatory ability (Fig. 2).The calibration curve shows that the calibration curve is basically close to the predicted curve and the ideal curve, with the Brier score = 0.132 and the Mean absolute error = 0.013,indicates a satisfactory level of accuracy in the model’s predictions (Fig. 3).Furthermore, the Hosmer-Lemeshow (H-L) fit curve was χ2 = 11.848, p = 0.158 > 0.05, the difference was not statistically significant, indicating that the model had a strong explanatory power and a good degree of fit.

Fig. 2
figure 2

ROC curve of the nomogram model

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Fig. 3
figure 3

Calibration curves

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Discussion

This study showed that the prevalence of H-type hypertension in Tibetan areas among the Tibetan population has reached a notable prevalence of 21.14%, surpassing the previous estimate of 15.1% among Tibetans residing in high-altitude regions [17]. Patients with H-type hypertension accounted for 84.31% of the total hypertensive population, higher than the baseline data of H-type hypertension in 79.68% of the hypertensive population in China from the Essential Stroke Prevention Study [18]. These results may be related to the local population’s exposure to low-pressure, low-oxygen environments, high salt and high-fat diets, and low intake of fresh fruits and vegetables.The H-type hypertension group exhibits a higher average age, with elevated levels of Hcy, TC, TG, LDL-C, UA and CREA compared to the other three groups. This may be due to a decrease in digestive and absorptive capacity with age, as well as impaired hepatic and renal metabolic function, resulting in decreased Hcy clearance. Furthermore, a high-sodium diet may impede the absorption of folate and B-complex vitamins, resulting in an abnormal elevation of plasma Hcy levels, thereby promoting the occurrence of H-type hypertension [25, 26]. The study suggests that TG and LDL-C are independent variables influencing disease progression [27]. Meta-analysis results indicate that in the overall genetic model of the human population, individuals carrying the TT genotype have an increased risk of develo** H-type hypertension [28]. Most studies rely on single logistic regression analysis, which has limitations in interpreting the results. Therefore, combining the construction of a risk prediction model tailored to the local population is of significant practical importance in preventing and controlling the development of H-type hypertension.Based on the results of multifactor logistic regression analysis, this study has developed a nomogram prediction model for H-type hypertension, incorporating seven factors. The model showed that the score increased by 6 points for every 5-year increase in age; the score increased by 9 points for every 200 umol/L increase in UA; the score increased by 5.5 points for every 2-mmol/L increase in TG; the score increased by 10 points for every 1-mmol/L increase in LDLC; and individuals with the TT genotype received a score of 8 points. The higher the total score, the greater the risk of develo** type h hypertension. Abnormal increases in the above indicators lead to varying degrees of risk for the development of H-type hypertension; therefore, it is recommended that the above indicators be included in the monitoring and management of H-type hypertension in the daily management of H-type hypertension.The model’s accuracy and discriminative ability were assessed using the H-L goodness-of-fit curve, AUC, and C-index index. The results indicate that this model possesses a high degree of discrimination and accuracy, making it a valuable tool for healthcare professionals from various fields to preliminarily assess individual disease risk and provide targeted prevention and treatment measures. Studies have demonstrated the efficacy of regular aerobic exercise in stabilizing blood pressure in individuals diagnosed with H-type hypertension [29]. This exercise program not only enhances cardiorespiratory endurance, but contributes to the improvement and management of the patient’s pathological state. Aerobic exercise may be considered as a treatment and management approach for the H-hypertensive population.

The participants in this study were Tibetan people in Tibet who have been living in a high-altitude environment at an average altitude of 4200 m. Further in-depth studies are needed to determine whether the group’s ability to adapt to high altitude, low pressure and low oxygen leads to a different genetic basis and whether the unique Tibetan dietary pattern of high salt and high fat, and low intake of fresh fruits and vegetables due to the survival environment causes differences in the prevalence of H-type hypertension.

Conclusion

The mutation occurring at the MTHFR C677T TT locus is a potential contributing factor to the development of H-type hypertension in the Tibetan population residing in Tibet. Additionally, age, UA, TG, LDL-C and the TT genotype are considered as risk factors for the onset of H-type hypertension in this population. Therefore, it is advocated that hypertensive patients should, in addition to routine blood pressure measurements, regularly monitor their homocysteine (Hcy) levels to prevent the synergistic effects between the two, and implement targeted preventive and control measures. These measures include strengthening health education in agricultural and pastoral regions, improving dietary patterns, promoting scientifically validated aerobic exercise, and incorporating rational interventions such as adequate folate intake.All of these efforts aim to improve the occurrence of adverse cardiovascular and cerebrovascular events.

Limitations

Our study has limitations due to its cross-sectional design, which precludes establishing causal relationships between risk factors and the occurrence of H-type hypertension. In terms of model validation, we only conducted internal validation and lack external validation to assess the model’s generalizability. Additionally, there is currently limited research on the genotypes of H-type hypertension patients in the Tibetan region. Therefore, it is necessary to conduct prospective multicenter cohort studies with larger sample sizes, encompassing various altitudes and geographical regions, to explore the relationship between genetic factors and H-type hypertension in the Tibetan population.