Gender-specific differences in associations between economic status and systolic blood pressure or diastolic blood pressure
Hypertension is a significant contributor to cardiovascular diseases, which are leading causes of global premature death and disability. In China, the prevalence of hypertension among adults aged 18 years and older was 23.2% in 2015. The relationship between socioeconomic status and blood pressure (BP) has been increasingly studied, with low socioeconomic status potentially influencing BP regulation unfavorably due to structural disadvantages in the social context. However, few studies have investigated gender differences in the association between low income and elevated BP, particularly among Chinese adults.
This observational study aimed to investigate the association of income and BP and address whether gender affects the impact of economic status on BP profile. A cross-sectional survey was conducted from September to November 2018 in Huanghua, a county-level city in Hebei Province, east China. The sample size of 6474 was estimated based on the prevalence of diabetes in Hebei Province (12.9%) and increased by 10% to account for possible incomplete information. Physical and laboratory examinations and standardized in-person interviews were conducted by licensed healthcare professionals using a simplified “China Chronic Disease and Risk Factor Surveillance Questionnaire.”
The study collected data on BP, weight, height, waist size, fasting glucose, and blood lipids. Smoking was defined as smoking one or more cigarettes in the previous month, and alcohol consumption as drinking any alcohol in the previous year. High-intensity physical activities included long-distance running, fast swimming, football, basketball, skipping, and aerobics, performed at least once a week. “Salty taste” was determined using a self-report qualitative question. Body mass index (BMI) was calculated, and participants were categorized as overweight or obese based on Chinese adult guidelines. Mean values of systolic BP (SBP) and diastolic BP (DBP) were calculated from three measurements. Abnormal blood lipids were defined as increased total cholesterol, triglycerides, or low-density lipoprotein cholesterol, or decreased high-density lipoprotein cholesterol. Diabetes mellitus was characterized by fasting blood glucose greater than 7.0 mmol/L or 126 mg/dL.
The study sample comprised 2991 men (44.6%) and 3714 women (55.4%). The mean SBP and DBP were 128.8 and 83.1 mmHg, respectively (129.5/83.8 mmHg for males and 128.3/82.6 mmHg for females). Annual household income was RMB 12,000 Yuan for males and RMB 10,000 Yuan for females.
Univariate analysis revealed that annual household income was significantly associated with SBP and DBP for females but not for males. Stratified multivariate analysis by gender showed that, after adjusting for confounding variables, annual household income per capita was significantly associated with SBP and DBP for females. Specifically, SBP and DBP decreased by 1.33 and 0.62 units, respectively, when income increased by 10,000 Chinese Yuan. However, there was no statistically significant difference in males for SBP or DBP.
The interaction effect between gender and income was significant in the SBP models but not in the DBP models, indicating that the relationship between income and SBP differed significantly by gender. Specifically, gender modified the associations of economic status with SBP. This study revealed a positive association of economic status with SBP and DBP among females. The interaction analysis indicated that gender may act as a modifier between economic status and SBP in the study population, with females and economic status having a synergy effect on SBP.
The exact pathways and mechanisms between income and BP remain unclear, but potential intermediary causes include individual health behaviors and/or risk factors, and accessibility and affordability of healthcare relevant to income-level inequities. One possible explanation for the “gender/income” interaction effect on SBP could be the different adaptation to stressors and allostatic load by gender, which may affect SBP regulation. Chronic stress, more common in low-income communities, may up-regulate the hypothalamic-pituitary-adrenal system, increasing allostatic load and stress-coping behaviors, and reducing the efficiency of BP regulatory mechanisms. Poverty may pressurize Chinese women more than men, resulting in elevated SBP only in females.
The study demonstrates that the influence of low economic status on elevated BP is both gender-specific and income-specific, with women with poor income at a greater risk of elevated BP. If these gender differences in susceptibility to poverty are robust, interventions for precise health poverty alleviation may require adjustment according to gender, and prevention of hypertension should emphasize females with low income.
doi.org/10.1097/CM9.0000000000000953
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