It is estimated that under these new guidelines, 103 million Americans have high blood pressure, up from 72 million under the previous standard. Nearly half of all American adults, and nearly 80 percent of those aged 65 and older, will find that they qualify for blood pressure medication and will need to take steps to reduce their blood pressure. High blood pressure increases the risk of having a heart attack or stroke, as well as several other diseases affecting the arteries in the body. The impact of blood pressure is strongest at very high levels of blood pressure (greater than 180 over 110) but is still significant at any level above 120 over 80. For someone in their 50s, a blood pressure of 160 over 100 increases the risk of having a heart attack or stroke by 50 percent compared with a blood pressure of 120 over 80.