Association of Blood Pressure With Cause-Specific Mortality in Mexican Adults

Abstract

Importance: Elevated blood pressure is a major cause of premature death, but there is little direct evidence demonstrating this association in studies of Hispanic populations.

Objective: To assess the association between blood pressure and cause-specific mortality in a large cohort of Mexican adults with a high prevalence of uncontrolled diabetes.

Design, setting, and participants: A total of 159 755 adults aged 35 years or older from 2 districts in Mexico City were recruited to this cohort study between April 1998 and September 2004 and followed up until January 2018. The present analyses focused on 133 613 participants who were aged 35 to 74 years and had no history of chronic disease besides diabetes.

Exposure: Blood pressure.

Main outcomes and measures: Cox regression, adjusted for confounders, yielded mortality rate ratios (RRs) for deaths of participants occurring between ages 35 and 74 years.

Results: Of the 133 613 participants (43 263 [32.4%] men; mean [SD] age, 50 [11] years), 16 911 (12.7%) had self-reported previously diagnosed diabetes (including 8435 [6.3%] with uncontrolled diabetes, defined as hemoglobin A1c ≥9%) and 6548 (4.9%) had undiagnosed diabetes. Systolic blood pressure (SBP) was associated with vascular mortality between ages 35 to 74 years, with each 20 mm Hg lower usual SBP associated with 35% lower vascular mortality (RR, 0.65; 95% CI, 0.61-0.68), including 48% lower stroke mortality (RR, 0.52; 95% CI, 0.47-0.59) and 32% lower ischemic heart disease mortality (RR, 0.68; 95% CI, 0.63-0.74). These RRs were broadly similar in those with and without diabetes. Compared with those without diabetes and SBP less than 135 mm Hg at recruitment, the vascular mortality RR was 2.8 (95% CI, 2.4-3.3) for those without diabetes and SBP of 155 mm Hg or greater, 4.7 (95% CI, 4.1-5.4) for those with uncontrolled diabetes and SBP less than 135 mm Hg, and 8.9 (95% CI, 7.2-11.1) for those with uncontrolled diabetes and SBP of 155 mm Hg or greater. Lower SBP was also associated with decreased kidney-related mortality (RR per 20 mm Hg lower usual SBP, 0.69; 95% CI, 0.64-0.74), decreased mortality from infection (RR, 0.81; 95% CI, 0.71-0.91), and decreased mortality from hepatobiliary disease (RR, 0.87; 95% CI, 0.78-0.98), but not decreased neoplastic or respiratory mortality. SBP was more informative for vascular mortality than other blood pressure measures (eg, compared with SBP, diastolic blood pressure was only two-thirds as informative).

Conclusions and relevance: Blood pressure was most strongly associated with vascular and kidney-related mortality in this Mexican population, with particularly high absolute excess mortality rates among individuals with diabetes. The findings reinforce the need for more widespread use of blood pressure-lowering medication in Mexico, particularly among those with diabetes.

Figure 1.. Association of Systolic Blood Pressure (SBP) With Cause-Specific Vascular Mortality Between Ages 35 and 74 Years

Analyses excluded participants with prior chronic diseases (ie, ischemic heart disease [IHD], stroke, chronic kidney disease, cirrhosis, cancer, or emphysema) apart from diabetes. The mortality rate ratios (RRs) for the 6 baseline SBP categories were plotted against the expected long-term usual SBP level in each group. The error bars through each point represent group-specific 95% CIs, with the area of each square proportional to the amount of statistical information. Estimates of RR were stratified by age-at-risk (in 5-year ranges) and are adjusted for sex, district of residence, highest education level attained, smoking status, alcohol intake, leisure-time physical activity, measures of anthropometry, and diabetes status.

Figure 2.. Association of Systolic Blood Pressure (SBP) With Vascular Mortality by Age and History of Previously Diagnosed Diabetes

Analyses excluded participants with prior chronic diseases (ie, ischemic heart disease, stroke, chronic kidney disease, cirrhosis, cancer, or emphysema) apart from diabetes. Within each age-at-risk group, the mortality rate ratio (RR) estimates in those with and without previously diagnosed diabetes were stratified by age-at-risk (in 5-year ranges) and adjusted for sex, district of residence, highest education level attained, smoking status, alcohol intake, leisure-time physical activity, and measures of anthropometry. The overall RR estimates are then also adjusted for diabetes. A test for trend in the log RR across the 3 age-at-risk categories shown yielded a χ² statistic of 21.5 (P < .001). Trends described in the heading of the point estimate line indicate lower and higher mortality associated with lower SBP.

Figure 3.. Absolute Excess Vascular Mortality Between Ages 35 and 74 Years Associated With Systolic Blood Pressure (SBP) by History and Control or Previously Diagnosed Diabetes

Analyses excluded participants with prior chronic diseases (ie, ischemic heart disease, stroke, chronic kidney disease, cirrhosis, cancer, or emphysema) apart from diabetes. For the 9 groups shown, the mortality rate ratio (RR) estimates are stratified by age-at-risk (in 5-year ranges) and adjusted for sex, district of residence, highest education level attained, smoking status, alcohol intake, leisure-time physical activity, and measures of anthropometry. The error bar extending above each column extends to the upper 95% confidence limit of the RR. The mean usual SBP in the 3 SBP categories shown was 121, 139, and 158 mm Hg, respectively.

Figure 4.. Association of Systolic Blood Pressure (SBP) With Nonvascular Mortality Between Ages 35 and 74 Years by History of Previously Diagnosed Diabetes

Analyses excluded participants with prior chronic diseases (ie, ischemic heart disease, stroke, chronic kidney disease, cirrhosis, cancer, or emphysema) apart from diabetes. For each cause of death, the mortality rate ratio (RR) estimates in those with and without previously diagnosed diabetes are stratified by age-at-risk (in 5-year ranges) and adjusted for sex, district of residence, highest education level attained, smoking status, alcohol intake, leisure-time physical activity, and measures of anthropometry. The overall RR estimates are then also adjusted for diabetes. Trends described in the heading of the point estimate line indicate lower and higher mortality associated with lower SBP. In addition to the nonvascular deaths shown, there were an additional 359 deaths between ages 35 and 74 from an acute diabetic crisis and 662 deaths from other known or unknown causes. The association between SBP and mortality from these other causes is shown in eFigure 7 and eFigure 8 in the Supplement.