It is more likely because there are two main effects in genetic struture of isolated communities:
1. There is a reduction of genetic variability due to genetic drift, because the genetic drift (random fluctuations in the frequency of a specific allele in a population) involves the loss of alleles, and in isolated populations there won't be any contact with different alleles anymore. So there will be more homozygous individuals, increasing the chance of recessive defects to occur.
2. There is an increase in consanguinity, because the mate options are limited. With more consanguinity, the chances of recessive defects to appear is increased too, as those recessive alleles are generally being inherited in a specific family.