Low heart rate in middle-aged men may present with clinical manifestations such as dizziness, blackouts, blurred vision and syncope. 1. The heart rate of normal healthy adults is 60~100 beats per minute, and when it is lower than 60 beats per minute, it is considered bradycardia. Bradycardia is physiologic in normal people during sleep and in athletes, but it can also be caused by heart diseases such as sinus node lesions or by taking certain medications. 2. When middle-aged men have a low heart rate, they may experience bradycardia, slow pulse, dizziness, headache, drowsiness, dark twilight, blurred vision, and in severe cases, fainting or even sudden death. This is caused by insufficient blood supply to the brain, heart and other organs due to low heart rate. Therefore, it is recommended to consult a doctor in time to identify the cause of the disease and receive standardized diagnosis and treatment.