From November 2014 to June 2016, we performed a hospital-based case-control study on EH in Fujian Province, China. Participants were recruited from the First Affiliated Hospital of Fujian Medical University and the Affiliated People’s Hospital of Fujian University of Traditional Chinese Medicine. A total of 402 EH patients were included in the final analysis. Meanwhile, 402 healthy controls were randomly selected from the physical examination population in the same hospitals, and were frequency-matched by gender and age (±3 years) with cases. The disease-free status was ascertained according to the results of physical examination. Furthermore, 80 of the 402 EH patients and 80 of the 402 control individuals were selected by stratified random sampling method to donate venous blood samples for ncRNA expression analysis by quantitative real-time polymerase chain reaction (qPCR). Inclusion criteria for cases included patients with at least three consecutive records of systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg or patients that have received antihypertensive medications for more than 3 months (European Society of Hypertension-European Society of Cardiology Guidelines, 2003). Inclusion criteria for controls included healthy individuals that have systolic blood pressure and diastolic blood pressure < 140 and < 90 mmHg, respectively. Exclusion criteria included a known history of leucopenia, thrombocytopenia or severe hepatic or renal dysfunction and evidence of an inflammatory or malignant disease. The protocol was approved by the ethics committee of Fujian Medical University School. Written informed consent was obtained from all patients and controls.

The participants completed the questionnaire themselves following instructions given by the researchers. The completed questionnaire was checked by the researchers to ensure that all questions have been answered appropriately. Questions covered demographic characteristics (e.g. gender, age, marital status, education level and occupation), lifestyle habits (e.g. tobacco smoking, alcohol drinking, diet, exercise, anxiety and depression levels) and family history of hypertension. Smokers were defined as individuals who smoked cigarettes more than once a day consecutively for more than 6 months or smoked more than 100 cigarettes cumulatively [17]. Alcohol drinkers were defined as subjects who had consumed any alcoholic beverage at least once per week for a minimum of 6 months [17]. A bland diet was defined as light food with no or very little oil, sugar, salt and spicy ingredients [17]. Occupational physical activities were classified into three categories depending on the intensity, duration and frequency of the participant’s physical activity at work. Light occupational physical activity was defined as 75% of the time for sitting or standing and 25% of the time for standing activities, such as office workers, salesmen and hotel waiters; moderate occupational physical activity was defined as 25% of the time for sitting or standing and 75% of the time for special activities, such as students’ daily activities, driving and electrical installation; and heavy occupational physical activity was defined as 40% of the time for sitting or standing and 60% of the time for special occupation activities, such as non-mechanised farming, dancing and mining [17]. The participants’ personality was classified into four types: participants with type A personality were defined as those who were always in a rush, highly productive, impulsive, stubborn and impatient; participants with type B personality were defined as those who were always in a soothing and self-regulating state; participants with type C personality were defined as those who always suppressed their emotions and had too much negative emotional experience; and participants with type D personality were defined as those who had the tendency to experience increased negative emotions most of the time and not share these emotions with others because of fear of rejection or disapproval [17]. Active exercise was defined as exercise lasting for at least 20 min once a week, whereas passive exercise was defined as exercise lasting less than 20 min once a week or no exercise at all [17]. Anxiety and depression were self-rated according to a previous report [17]. The self-rating anxiety scale (SAS) was defined as follows: < 50 normal, 50–59 mild anxiety, 60–69 moderate anxiety and ≥ 70 severe anxiety. The self-rating depression scale (SDS) was defined as follows: < 53 normal, 53–62 mild anxiety, 63–73 moderate anxiety and ≥ 74 severe anxiety.

Systolic and diastolic blood pressure, height, weight and waist circumference (WC) were measured. Before blood pressure measurement, each subject was asked to not smoke, drink any beverage with caffeine or exercise for at least half an hour. After resting in a sitting position for 5 min, brachial blood pressure was measured three times with an interval of 2 min; the average of three readings was used for analysis [17]. Body mass index (BMI) was calculated as weight (kg) divided by the square of height in meters (m²) and categorised into four scales: < 18.5 underweight, 18.5–24.0 normal, 24.0–28.0 overweight and ≥ 28.0 obesity [17]. WC was classified into two categories: the waist of males < 85 cm or waist of females < 80 cm was considered normal, whereas waist of males ≥85 cm or waist of females ≥80 cm was considered abdominal obesity [17].

Blood samples were collected in a K2-EDTA-coated tube (BD Biosciences, California, USA) and centrifuged at 400 g for 10 min to remove plasma. According to the manufacturer’s instructions for the Lymphocyte Separation Medium (Hao Yang Biological Manufacture Co., Ltd., Tianjin, China), blood samples were carefully transferred into a new RNA-free tube for a second centrifugation at 400 g for 20 min to obtain the peripheral blood leucocytes and then stored at − 80 °C prior to RNA extraction. All blood samples were subjected to only one freeze-thaw cycle.

Total RNA was extracted from peripheral blood leucocytes using TRIzol reagent (Invitrogen, California, USA) and dissolved in RNase-free water. RNA extracts were quantified using NanoDrop 2000 instrument (Thermo Scientific, USA). The integrity of the RNA was determined by agarose gel electrophoresis. Reverse transcription of quantified RNA was performed using PrimeScript RT Reagent Kit with gDNA Eraser (lncRNAs) or the PrimeScript RT Reagent Kit (miRNAs) (Takara Bio Inc., Shiga, Japan) according to the manufacturer’s instructions. qPCR was performed on the LightCycler 480 real-time PCR system (Roche, Switzerland) with the SYBR® Premix Ex Taq™ II kit (Takara Bio Inc., Shiga, Japan). Amplification curves were obtained by 40 cycles of 95 °C for 30 s, 95 °C for 5 s and 60 °C for 34 s, whereas dissolution curves were obtained by one cycle of 95 °C for 15 s, 60 °C for 1 min and 95 °C for 15 s. The Ct value was the fractional cycle number at which the fluorescence exceeded the given threshold. GAPDH and U6 were used as internal controls. The reverse primer used for miRNA was a universal downstream primer. LncRNA and miRNA expression levels were calculated using the 2^-△△CT method [18]. The primers used for qPCR are listed in Table 1.

All data were analysed using SPSS 22.0 (SPSS Inc., Chicago, IL, USA). Comparisons between the case and control groups were performed using a Z-test or Chi-square analysis. Multiple factor logistic regression was used to analyse whether lncRNAs and miRNAs were influencing factors of EH. All tests were two sided and a P value < 0.05 was considered statistically significant.

Associations between demographic characteristics and EH are shown in Table 2. No significant difference was found in the general demographic characteristics between the case and control groups, including gender, age, marital status, education and occupation (all P > 0.05), indicating that the frequency matching was adequate. Associations between risk factors and EH are shown in Table 3. Compared with controls, EH patients had a lower bland diet rate (61.2% versus 75.6%, χ ² test, P <  0.001), higher abdominal obesity rate (84.0% versus 64.7%, χ ² test, P <  0.001) and higher family history of hypertension rate (47.0% versus 19.5%, χ ² test, P <  0.001). Significant differences were found between cases and controls in the occupational physical activities, personality types, anxiety levels and body mass indices.

When lncRNA levels between hypertensive patients and controls were compared, we found that NR_027032 (Z-test = − 2.439, P = 0.015) and NR_034083 (Z-test = − 2.890, P = 0.004) were significantly reduced, whereas NR_104181 (Z-test = − 2.685, P = 0.007) was significantly elevated in hypertensive patients compared with controls (Table 4). When miRNA levels between hypertensive patients and controls were compared, we found that miR-143 (Z-test = − 2.797, P = 0.005) and miR-145 (Z-test = − 2.436, P = 0.015) were up-regulated in hypertensive patients compared with controls, whereas miR-126 level (Z-test = − 1.679, P = 0.093) was not significantly different between hypertensive patients and controls (Table 4).

We used EH as the dependent variable (0 = no, 1 = yes) and bland diet, occupation physical activities, personality type, anxiety level, BMI, abdominal obesity and family history of hypertension as independent variables for multivariate logistic regression analysis (assignment results are shown in Table 5, wherein personality type and BMI were used as dummy variables). After adjusting the demographic and environmental factors, logistic analysis showed that lower expression levels of NR_034083 (OR = 0.528, 95% CI = 0.322–0.866) were a protective factor against hypertension, whereas higher expression levels of NR_104181 (OR = 1.651, 95% CI = 1.164–2.342) and miR-143 (OR = 1.538, 95% CI = 1.182–2.000) were risk factors (Table 6).