Hornbeam leaf retention

I was just wondering if anyone else thinks that hornbeams in general aren't retaining their leaves as well as usual this year.  I know that over 2m high and more mature plants drop leaves more but looking around at the hornbeams I pass when I'm walking they pretty much all are looking very bare compared to previous years.  I'm wondering if maybe something about the weather last summer is a factor?  Can anyone shed any light on this?  Thanks.