Chapter 10: Hypertension and diabetes

Epidemiology and risk classification

Hypertension is common in type 1 diabetes and even more common in type 2 diabetes. Type 1 diabetes usually begins in childhood, adolescence or before age 30, and hypertension is more prevalent than in people of the same age without diabetes. Older population studies and a European study of more than 3,000 people reported hypertension in approximately 15% of people with type 1 diabetes. Diabetic kidney disease, usually identified by increased urinary protein, is a common cause, although some people—often with a strong family history—develop hypertension without obvious kidney disease.

Hypertension in diabetes is associated with typical HMOD and cardiovascular outcomes and requires antihypertensive treatment. The evidence base comes mainly from type 2 diabetes and supports starting treatment around 140/90 mmHg, then pursuing a target below 130/80 mmHg when tolerated, using combinations from the major drug classes including renin–angiotensin-system blockers.

Type 2 diabetes and hypertension share causal pathways and interact in both directions. Insulin-related activation of the central nervous system, insulin resistance and higher insulin levels can increase sympathetic activity. Compared with non-diabetic hypertension, diabetes is more often accompanied by higher systolic pressure, wider pulse pressure, greater variability, non-dipping at night, salt sensitivity, a tendency to hyperkalaemia and orthostatic hypotension, particularly as diabetes duration increases. Masked hypertension and resistant hypertension are also more common.

Diabetes itself substantially increases cardiovascular risk, regardless of HMOD, established cardiovascular disease or CKD. Only people with recent, well-controlled diabetes of less than ten years, without HMOD or additional cardiovascular risk factors, may be classified as moderate risk. Otherwise risk is high or very high, especially with cardiovascular disease or advanced CKD. People with diabetes and hypertension are therefore candidates for prompt antihypertensive medication together with lifestyle intervention.

Benefits of lowering blood pressure

Strong evidence supports blood-pressure lowering in people with hypertension and type 2 diabetes to reduce major vascular events and mortality and to prevent microvascular complications such as nephropathy and retinopathy. Protection is less certain for every diabetes-related microvascular complication, including possible effects on autonomic neuropathy.

Lifestyle measures are particularly important in type 2 diabetes, especially interventions targeting overweight and obesity that also improve glucose and metabolic abnormalities. Drug treatment should begin when systolic pressure is above 140 mmHg or diastolic pressure above 90 mmHg, aiming for below 130/80 mmHg if well tolerated. RCT analyses suggest additional protection at these lower values, particularly against stroke.

ACCORD supports a systolic target below 130 mmHg: in people with type 2 diabetes, an on-treatment systolic pressure around 122 mmHg was associated with fewer strokes than 130–139 mmHg. Intensive lowering did not reduce the composite cardiovascular outcome or all-cause mortality in the overall factorial trial, possibly because of the study design and the harmful effect of intensive glucose lowering. After accounting for that effect, the benefit of intensive pressure lowering extended to the composite cardiovascular outcome.

Although some recent studies have proposed a systolic target below 120 mmHg, other evidence does not support such a low target for everyone. Current guidance generally recommends systolic pressure below 130 mmHg but not below 120 mmHg, and diastolic pressure below 80 but not below 70 mmHg. In ONTARGET, events increased at diastolic values slightly below 70 mmHg; other analyses suggest that baseline diastolic pressure should not prevent an individualised systolic target. If below 130/80 cannot be achieved or tolerated, maintaining 130–139/80–89 mmHg still provides important protection compared with 140/90 mmHg.

Antihypertensive treatment

Starting with a two-drug combination and using combinations in most patients is particularly relevant in diabetes because control is difficult and cardiovascular risk is high. Treatment must still be intensified cautiously, with attention to orthostatic hypotension in older people and in long-standing diabetes with possible autonomic dysfunction.

All major antihypertensive classes reduce cardiovascular outcomes in type 2 diabetes. Treatment should include a renin–angiotensin-system blocker when appropriate because outcome trials show stronger kidney protection: less new microalbuminuria, lower protein excretion in proteinuric disease, slower GFR decline in diabetic and non-diabetic kidney disease and prevention of kidney failure.

Newer diabetes drugs also reduce vascular complications. SGLT2 inhibitors provide important protection against heart failure and kidney outcomes beyond glucose lowering. GLP-1 receptor agonists reduce cardiovascular events and produce substantial weight loss. ESC/EASD guidance recommends these agents early in people with previous cardiovascular events, HMOD or multiple risk factors. Both classes can lower office and ambulatory pressure by several mmHg even during multidrug antihypertensive treatment. Finerenone, a newer non-steroidal MRA, also provides cardiovascular and kidney protection in diabetic kidney disease and produces a small but meaningful pressure reduction.