The Problem

High blood pressure is the single greatest risk factor for negative cardiovascular outcomes.^1,2 As a marker for cardiovascular health, systolic blood pressure (SPB) in particular has strong supporting evidence.^2,3 In one meta-analysis, a 20 mm Hg change in SPB was associated with a twofold (or more) increase in stroke death, ischemic heart disease, and mortality from other vascular causes for middle-aged individuals.⁴

Hypertension accounts for 12.8% of total human mortality.²²

An analysis of NHANES data shows that high SPB is common in older individuals—about 30% of patients not being treated for hypertension had SPB at 140 mm Hg.⁵ That puts those untreated patients at hypertension stage 2, according to the American College of Cardiology’s 2017 Guideline for High Blood Pressure in Adults⁶ (though they would be only on the cusp for antihypertensive medication under the JNC 8 guidelines).⁵ Even in individuals without hypertension, higher SPB variability is associated with higher mortality,^7,8 cardiovascular disease, stroke, and end-stage renal disease.⁸

Modifiable Risk Factors: Focus on Air Pollution

Along with antihypertensive agents, diet and lifestyle play a large role in the management of hypertension.^9,10 In addition to these mainstays of treatment, management of exposure to air pollution has emerged as a potentially useful intervention. Increased exposure to particulate matter <2.5 (PM_2.5), commonly released by combustion vehicles, is associated with increased blood pressure.^11,1

A new study of seniors in Detroit demonstrates that even short-term (three-day) use of a portable HEPA air filter reduced systolic BP (PM_2.5) by an average of 3.2 mm.¹³ Both low-efficiency and high-efficiency air filtration significantly reduced SBP, and the effect was greater for patients with obesity.¹³ Though the study was small (n=40), its rigorous design (a randomized, double-blind, three-way crossover intervention study) and the low-cost, low-harm nature of the intervention warrants consideration.¹³ Most of the participants were African American, a group shown to have higher risk for hypertension.^14,15,16 The high-efficiency HEPA filter reduced exposure to PM_2.5 significantly, by over 50%.¹³

In the US, hypertension accounts for 50% of the racial differences in mortality between African Americans and white Americans.¹⁴

With longer exposure to cleaner air, outcomes may improve even more, especially in the subgroup of obese patients. One very large study in China found that over three years, blood pressure increases were associated with PM_2.5 exposure even in young, healthy individuals.¹⁷ In older Americans, increased exposure to PM_2.5 over a one-year period increased both blood pressure and SBP.¹⁸ Given that ambient particulate matter is the sixth leading cause of death globally,¹⁹ reductions in exposure and attenuation of resulting health effects could have a major impact on many patients.

Balance & Outcomes

However, balance is key, even with systolic blood pressure. Lowering SPB below 110 mmHg in older individuals leads to greatly increased rates of falls and syncope—approximately 50% higher in individuals with a mean SPB below 110.²⁰ Thirty percent of the patients studied (all of whom were on medication for hypertension) had a mean or minimum SPB below 110, suggesting that in hypertensive individuals, monitoring for medication-induced hypotension may be needed as well.²⁰

More than one in three American adults have persistently elevated blood pressure.²²

In addition to potentially reducing hypertension and cardiovascular events, lowered exposure to particulate matter may have other, wide-reaching effects. For instance, reducing variability in SPB (and other metabolic parameters) may help to reduce the risk of Alzheimer’s and dementia.²¹

Read a related article about the microbiome and arterial stiffness

References

1. Bromfield S, Muntner P. High blood pressure: the leading global burden of disease risk factor and the need for worldwide prevention programs. Curr Hypertens Rep. 2013;15(3):134-136. doi:1007/s11906-013-0340-9.
2. GBD 2015 Risk Factors Collaborators. Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016;388(10053):1659-1724. doi:1016/S0140-6736(16)31679-8.
3. Mourad JJ. The evolution of systolic blood pressure as a strong predictor of cardiovascular risk and the effectiveness of fixed-dose ARB/CCB combinations in lowering levels of this preferential target. Vasc Health Risk Manag. 2008;4(6):1315-1325.
4. Lewington S, Clarke R, Qizilbash N, Peto R, Collins R; Prospective Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. 2002;360(9349):1903-1913. doi:10.1016/S0140-6736(02)11911-8.
5. Shimbo D, Tanner RM, Muntner P. Prevalence and characteristics of systolic blood pressure thresholds in individuals 60 years or older. JAMA Intern Med.2014;174(8):1397-1400. doi:1001/jamainternmed.2014.2492.
6. Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2018;71(19):e127-e248. doi:1016/j.jacc.2017.11.006.
7. Muntner P, Shimbo D, Tonelli M, Reynolds K, Arnett DK, Oparil S. The relationship between visit-to-visit variability in systolic blood pressure and all-cause mortality in the general population: findings from NHANES III, 1988 to 1994. Hypertension. 2011;57(2):160-166. doi:1161/HYPERTENSIONAHA.110.162255.
8. Gosmanova EO, Mikkelsen MK, Molnar MZ, et al. Association of systolic blood pressure variability with mortality, coronary heart disease, stroke, and renal disease. J Am Coll Cardiol. 2016;68(13):1375-1386. doi:1016/j.jacc.2016.06.054.
9. Shimbo D. Dietary and lifestyle factors in hypertension. J Hum Hypertens. 2016;30(10):571-572. doi:1038/jhh.2016.57.
10. Ferdinand KC, Nasser SA. Management of essential hypertension. Cardiol Clin. 2017;35(2):231-246. doi:1016/j.ccl.2016.12.005.
11. Rumchev K, Soares M, Zhao Y, Reid C, Huxley R. The association between indoor air quality and adult blood pressure levels in a high-income setting. Int J Environ Res Public Health. 2018;15(9):E2026. doi:3390/ijerph15092026.
12. Dvonch JT, Kannan S, Schulz AJ, et al. Acute effects of ambient particulate matter on blood pressure: differential effects across urban communities. Hypertension. 2009;53(5):853-859. doi:1161/HYPERTENSIONAHA.108.123877.
13. Morishita M, Adar SD, D’Souza J, et al. Effect of portable air filtration systems on personal exposure to fine particulate matter and blood pressure among residents in a low-income senior facility: a randomized clinical trial. JAMA Intern Med.2018;178(10):1350-1357. doi:1001/jamainternmed.2018.3308.
14. Musemwa N, Gadegbeku CA. Hypertension in African Americans. Curr Cardiol Rep. 2017;19(12):129. doi:1007/s11886-017-0933-z.
15. Ortega LM, Sedki E, Nayer A. Hypertension in the African American population: a succinct look at its epidemiology, pathogenesis, and therapy. Nefrologia. 2015;35(2):139-145. doi:1016/j.nefro.2015.05.014.
16. Ferdinand KC, Armani AM. The management of hypertension in African Americans. Crit Pathw Cardiol. 2007;6(2):67-71. doi:1097/HPC.0b013e318053da59.
17. Xie X, Wang Y, Yang Y, et al. Long-term effects of ambient particulate matter (with an aerodynamic diameter ?2.5 ?m) on hypertension and blood pressure and attributable risk among reproductive-age adults in China. J Am Heart Assoc. 2018;7(9):e008553. doi:1161/JAHA.118.008553.
18. Honda T, Pun VC, Manjourides J, Suh H. Associations of long-term fine particulate matter exposure with prevalent hypertension and increased blood pressure in older Americans. Environ Res. 2018;164:1-8. doi:1016/j.envres.2018.02.008.
19. GBD 2016 Risk Factors Collaborators. Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016.  2017;390(10100):1345-1422. doi:10.1016/S0140-6736(17)32366-8.
20. Sim JJ, Zhou H, Bhandari S, et al. Low systolic blood pressure from treatment and association with serious falls/syncope. Am J Prev Med. 2018;55(4):488-496. doi:1016/j.amepre.2018.05.026.
21. Lee SH, Han K, Cho H, et al. Variability in metabolic parameters and risk of dementia: a nationwide population-based study. Alzheimers Res Ther. 2018;10(1):110. doi:1186/s13195-018-0442-3.
22. Ali A, Abu Zar M, Kamal A, et al. American Heart Association High Blood Pressure Protocol 2017: a literature review. Cureus. 2018;10(8):e3230. doi:7759/cureus.3230.

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