Final answer:
Smoking is the most important preventable cause of premature death in women, as it substantially increases the risk of respiratory, cardiovascular diseases, and cancer.
Step-by-step explanation:
The most important preventable cause of premature death in women is smoking. Smoking is a significant cause of respiratory diseases, cardiovascular diseases, and cancer. The exposure to tobacco smoke, whether by smoking directly or through secondhand smoke, is identified as the leading cause of preventable death. It leads to numerous health issues and is associated with a decrease in life expectancy by about 10 years for regular smokers compared to non-smokers. Factors such as obesity, high blood pressure, and lack of exercise are also major risk factors for chronic diseases; however, the preventive potential of ceasing smoking is exceptionally high.
Additionally, while heart disease is the leading cause of death and can be attributed to sedentary lifestyles and high trans-fat diets, it is preventable by modifying different lifestyle risk factors, including smoking cessation. Healthy behaviors, such as proper nutrition and physical activity, substantially lower the risk for heart disease, but avoiding tobacco stands as the single most significant action to prevent early mortality.