Two Things Changing Together
Both patterns say that as one thing progresses, another changes alongside it.
- 年を取るにつれて体力が落ちる。(As you age, your stamina declines.)
The change must be gradual and unintentional. A one-off event does not fit.
The Difference Between Them
They overlap heavily, but にしたがって has a second meaning つれて lacks:
| Pattern | Senses |
|---|---|
| につれて | gradual parallel change only |
| にしたがって | gradual parallel change and "in accordance with (a rule)" |
- 指示にしたがって行動してください。(Act in accordance with the instructions.)
That second sense — following an order or a rule — is にしたがって only.
Both Halves Must Change
The pattern needs change on both sides. A static second clause is wrong:
- ○ 時間がたつにつれて痛みが薄れた
- × 時間がたつにつれて病院に行った
Against ば〜ほど
ば〜ほど repeats the same word and stresses proportion. につれて links two different processes and stresses accompaniment.