Published in Medicine and Science in Sports and Exercise, an Iowa State University study looking exercise-related activity over time, of nearly 13000 people, showed it doesn't necessarily take a lot of time to reduce the risk of heart attacks and strokes.
The results - some of the first to look at resistance exercise and cardiovascular disease - show benefits of strength training are independent of running, walking or other aerobic activity. In other words, you do not have to meet the recommended guidelines for aerobic physical activity to lower your risk; weight training alone is enough. (Science Daily, Nov 13 2018)
As for spending less than an hour a week on strength training, we all know there are other benefits, such as strengthened bones, physical strength, lower cholesterol, less fat (major factors as we age) are vitally improved, as is aerobic capacity, to varying levels depending on program design. (See How Circuits can give you cardio benefits in a strength-training format)
The article's here: Weightlifting is good for your heart and it doesn't take much