每日一句(57-18/09/09)：中年男人三大杀手

Failing to give up smoking or to control blood pressure and cholesterol were reported to reduce life expectancy by 10 to 15 years. (From NHS, September 18 2009: Male habits knock decade off life)

如果不戒烟、不控制血压和胆固醇，寿命预期会减少10到15岁。

1、为什么用“were”不用“was”？
2、表示减少/增加，用介词by。
3、were reported to的叙述方式。