High blood pressure results from a combination of factors, not a single cause. Genetics account for roughly 40% of the variation in blood pressure between people, while the rest comes from diet, body composition, physical activity, sleep, kidney function, and the natural aging of your arteries. Blood pressure is classified as high (stage 1 hypertension) starting at 130/80 mm Hg, according to the most recent 2025 guidelines from the American Heart Association and American College of Cardiology.
How Your Body Regulates Blood Pressure
To understand what pushes blood pressure up, it helps to know the system that controls it. Your kidneys are the central player. When blood pressure drops, your kidneys release an enzyme called renin into your bloodstream. Renin triggers a chain reaction: it converts a protein made by your liver into an inactive hormone, which then gets converted in your lungs and kidneys into an active hormone that does two things. First, it causes the muscular walls of small arteries to tighten, which directly raises pressure. Second, it signals your adrenal glands and pituitary gland to release hormones that tell your kidneys to hold onto sodium and water.
More sodium in your blood means your body retains more water. More water means higher blood volume. Higher blood volume means higher pressure against your artery walls. This feedback loop, sometimes called the RAAS, is the master control system for blood pressure. When it works correctly, it keeps pressure stable. When something disrupts it, whether that’s too much dietary sodium, kidney damage, or hormonal imbalances, blood pressure climbs and stays elevated.
Sodium, Potassium, and the Balance Between Them
Sodium gets most of the attention, and for good reason. It directly increases water retention and blood volume. But recent research suggests that the ratio of potassium to sodium matters more than sodium intake alone. The optimal ratio is roughly three parts potassium to one part sodium. Most people eating a typical Western diet get this backward, consuming far more sodium than potassium.
Potassium helps keep blood vessel walls relaxed and pliable. When potassium is low relative to sodium, your vessels stiffen and your kidneys hold onto more fluid. This is a large part of why the DASH diet, which emphasizes fruits, vegetables, and whole grains (all rich in potassium), produces significant blood pressure reductions. It’s not just about cutting salt. It’s about flooding your system with the mineral that counterbalances salt’s effects.
Genetics and Family History
About 40% of the variation in blood pressure across populations is heritable, based on decades of twin and family studies. More recent genomic research has refined this, finding that identifiable genetic variants explain 20% to 49% of blood pressure variation depending on the population studied. There is no single “hypertension gene.” Instead, hundreds of small genetic variants each nudge your blood pressure slightly higher or lower. The cumulative effect determines your baseline risk.
What this means practically: if both your parents had high blood pressure, your risk is substantially higher than average, but it’s not inevitable. The other 60% of the equation is modifiable. Genetics set the starting line, not the finish.
How Arteries Stiffen With Age
Your arteries are meant to be elastic. They expand when your heart pumps and recoil between beats, which cushions the force of blood flow. Over time, the elastic fibers in artery walls break down and get replaced by collagen, a stiffer structural protein. This process accelerates with repeated pulsatile stress, meaning every heartbeat contributes a tiny amount of wear.
The result is isolated systolic hypertension, where the top number rises while the bottom number stays normal or even drops. This is the most common form of high blood pressure in people over 60. It happens because stiff arteries can no longer absorb the surge of blood from each heartbeat, so peak pressure climbs. High blood sugar accelerates this process by promoting collagen cross-linking, which is one reason diabetes and hypertension so frequently occur together.
Insulin Resistance and Metabolic Factors
Insulin resistance, the condition underlying type 2 diabetes and prediabetes, contributes to high blood pressure through a specific and somewhat counterintuitive mechanism. When your cells stop responding well to insulin’s signal to absorb glucose, your body compensates by producing more insulin. The elevated insulin levels don’t effectively move sugar into cells, but they do retain their ability to tell your kidneys to reabsorb sodium. The result is a state of salt overload even if your dietary sodium intake is moderate.
Insulin resistance also stimulates collagen production in artery walls and triggers inflammatory processes that make vessels less flexible. Excess body fat, particularly around the abdomen, is the most common driver of insulin resistance. This creates a compounding effect: the metabolic dysfunction raises blood pressure through multiple pathways simultaneously.
Alcohol Consumption
A 2023 dose-response meta-analysis published in Hypertension found no safe threshold for alcohol and blood pressure. The relationship is linear: any amount of alcohol is associated with higher systolic blood pressure compared to not drinking. Even a single standard drink per day (about 12 grams of alcohol) was linked to a systolic increase of roughly 1.25 mm Hg. That sounds small, but across a population, it translates into a meaningful increase in cardiovascular events.
The effect becomes more pronounced with heavier drinking, and the association holds for both systolic and diastolic pressure. Previous claims that moderate drinking protected heart health have not held up under more rigorous analysis.
Sleep Apnea and the Nervous System
Obstructive sleep apnea is one of the most underrecognized contributors to high blood pressure, especially blood pressure that doesn’t respond well to medication. Among people with resistant hypertension (high blood pressure despite taking three or more medications), 82% have sleep apnea. In those with refractory hypertension, the most treatment-resistant form, the prevalence reaches nearly 100%.
The mechanism centers on your sympathetic nervous system, the “fight or flight” branch. Each time your airway collapses during sleep, oxygen levels drop. Your body responds with a surge of stress hormones that constrict blood vessels and raise heart rate. This happens dozens or even hundreds of times per night. Over months and years, your nervous system becomes chronically overactivated, keeping blood pressure elevated even during waking hours. If your blood pressure remains high despite lifestyle changes and medication, undiagnosed sleep apnea is one of the first things worth investigating.
Kidney Disease Creates a Feedback Loop
Chronic kidney disease and high blood pressure feed each other. As kidney function declines and fewer filtering units remain, each surviving unit must work harder. The body raises blood pressure to maintain adequate blood flow through these remaining filters. At the same time, damaged kidneys lose the ability to excrete sodium efficiently, leading to fluid retention that further raises pressure.
The overactive sympathetic nervous system in kidney disease also stimulates renin production, amplifying the same hormonal cascade that controls blood pressure in healthy people. Higher levels of the hormones that constrict blood vessels then further stimulate the sympathetic nervous system, creating a self-reinforcing cycle. This is why kidney disease often leads to blood pressure that’s difficult to control without addressing the kidney problem directly.
Physical Activity and Its Effects
Regular aerobic exercise produces the largest reductions in blood pressure of any single lifestyle change. In people with hypertension, consistent aerobic training lowers systolic pressure by about 7 mm Hg and diastolic by about 5 mm Hg. That’s comparable to what some blood pressure medications achieve.
Traditional weight training produces more modest reductions, roughly 2 mm Hg for both systolic and diastolic. Isometric exercises (holding a position under tension, like wall sits or sustained grip exercises) have shown surprisingly strong results in smaller studies, with reductions around 5/5 mm Hg. The mechanisms differ: aerobic exercise improves how well your blood vessels dilate, while resistance and isometric training appear to reduce resting nervous system activity. A mix of all three likely offers the most benefit, though aerobic exercise remains the strongest evidence-based approach for blood pressure specifically.
Physical inactivity contributes to hypertension not just through deconditioning but by promoting insulin resistance, weight gain, and arterial stiffness, the same factors that independently raise blood pressure through their own pathways.