Here are some ways to connect two ideas when one idea is the cause (the reason why) and the other is the result (the consequence).
It was difficult to follow him because he spoke very fast.
We put on lots of clothes because it was very cold.
Two other ways of saying because are as and since. We can use all of them before the basic sentence, too:
Because he spoke fast, it was difficult to follow him.
As it was very cold, we put on lots of clothes.
Nobody answered the door, so I left a message and went away.
It was very cold, so we put on lots of clothes.
NOTICE: Because + REASON and so + CONSEQUENCE cannot make sentences alone. They must have a basic sentence with them.
The weather was terrible. As a result, the train was late.
He spoke very fast. As a result, we couldn't follow.
Two other ways of writing as a result are consequently and therefore. We use all of them mainly in writing.
BUT WE CANNOT USE As a result for consequences of personal decision. For example, the sentences in 2 above.
He spoke so fast that nobody could understand him.
It was so cold that I couldn't feel my hands or feet.
He was such a fast speaker that nobody could understand him.
It was such cold weather that I couldn't feel my hands.