Blood pressure, the force of blood against artery walls, is a fundamental indicator of cardiovascular health. The definition of a “normal” reading has evolved significantly over time, reflecting advancements in medical research and a deeper insight into its long-term effects. This article explores the understanding and guidelines for blood pressure in 1970.
Defining Normal Blood Pressure in 1970
In 1970, medical professionals considered blood pressure acceptable at levels now classified as elevated or hypertensive. A common rule of thumb allowed for systolic blood pressure (the top number) to be approximately 100 plus the patient’s age. For example, a 60-year-old might have a systolic reading of 160 mmHg without immediate concern.
The threshold for hypertension was set at or above 160/95 mmHg (systolic/diastolic). Doctors aimed to reduce blood pressure to below 160 mmHg in patients with high readings. Early Joint National Committee guidelines emphasized diastolic pressure as the primary indicator of cardiovascular risk, with less focus on specific systolic goals.
Medical Understanding and Measurement in the 1970s
During the 1970s, the medical community’s understanding of hypertension developed. While some practitioners previously viewed high blood pressure as a compensatory mechanism, growing evidence began to reveal its detrimental effects. Influential research, such as the Framingham Heart Study, demonstrated that high blood pressure was a significant risk factor for conditions like coronary heart disease and stroke.
The Veterans Administration Cooperative Study trials, including one in 1970, provided compelling evidence that treating high blood pressure yielded clear health benefits. These findings spurred public health initiatives, such as the formation of the National High Blood Pressure Education Program in the early 1970s, aimed at raising awareness and promoting treatment.
Blood pressure measurement in 1970 largely relied on the auscultatory method, using a manual cuff and a mercury sphygmomanometer. Healthcare providers would inflate the cuff around the upper arm and then slowly release the pressure while listening for Korotkoff sounds through a stethoscope. The first sound indicated the systolic pressure, and the disappearance or muffling of sounds marked the diastolic pressure. While the oscillometric method, which uses automated devices, was being developed around this time, manual measurement remained the standard clinical practice.
The Shifting Landscape of Blood Pressure Guidelines
Since 1970, blood pressure guidelines have undergone significant revisions, driven by continuous research and a deeper understanding of cardiovascular risk. Advances in long-term studies have shown that the risk of heart attack, stroke, and kidney disease increases progressively with blood pressure levels, even at what were once considered “normal” readings.
A significant shift occurred with the 2017 guidelines from the American College of Cardiology and American Heart Association, which redefined hypertension. The threshold for Stage 1 hypertension was lowered from 140/90 mmHg to 130/80 mmHg. Today, a normal blood pressure is considered to be less than 120/80 mmHg. This change reflects a more aggressive approach to identifying and managing elevated blood pressure, aiming to intervene earlier to prevent long-term complications.