Heart and metabolic health

Heart and metabolic health covers the state of the heart and blood vessels and the body's handling of blood sugar, blood fats and body fat, which are closely linked. Cardiovascular disease, mainly heart attack and stroke, is the leading cause of death worldwide, with 18.6 million deaths in 2019 [1]. Most of it builds up over decades from a small set of measurable factors: in a study comparing heart attack patients with similar people who had not had one, in 52 countries, nine factors that can be changed, including abnormal blood fats, smoking, high blood pressure, diabetes and excess fat around the waist, accounted for 90% of the population attributable risk (the share of cases statistically explained by the factors) in men and 94% in women [2]. US adults with high scores on a combined measure of cardiovascular health had about 8.9 more years of life expectancy at age 50 than those with low scores [3].

Blood pressure and cholesterol are the two main measurable causes of artery damage, and both respond to treatment. About 1.28 billion adults aged 30 to 79 had hypertension (persistently high blood pressure) in 2019, and fewer than one in four of them had it controlled [4]. In pooled randomised trials (studies that assign participants to groups by chance), each 10 mm Hg reduction in systolic blood pressure (the upper number in a reading) lowered major cardiovascular events (serious heart and circulation events such as heart attack and stroke) by 20% [5], and each 1 mmol/L (about 39 mg/dL) reduction in LDL cholesterol (the cholesterol that builds up in artery walls) lowered major vascular events by about 22% [6].

Metabolic health and type 2 diabetes describes how the body regulates blood sugar and insulin, and the progression from insulin resistance (a poor response to the blood-sugar-lowering hormone insulin) to diabetes, which was associated with more than twice the odds of heart attack in the 52-country study [2]. Body weight covers the relationship between weight, body fat distribution and lifespan; excess weight raises blood pressure, and systolic pressure fell by about 1 mm Hg per kilogram lost in randomised trials [7]. Heat exposure describes sauna and hot tub bathing and the research on their associations with blood pressure and cardiovascular outcomes. Body mass index, blood sugar, blood pressure and non-HDL cholesterol (total cholesterol minus the HDL kind carried back to the liver) are four of the eight components of the cardiovascular health score used in the life-expectancy estimate above [3].