Cepheids metal abundance changes = cyclic?

[tu144]

I've run into a sentence
"The atomospheres of stars like Cepheids, having effective temperatures typical of G and K supergiants, are affected by changes in the atmospheric metal abundance."
Are these changes cyclic (one Cepheid variable star changes it's metal abundance in cyclic maner) or they just distinguish different types of Cepheids?

[StupendousMan]

One particular star will not change its metal abundance in the atmosphere appreciably during the period of time that it pulsates as a Cepheid, I would say. It makes more sense to discuss the effect that metallicity has from one star to another; that is, a high-metallicity Cepheid will have a different color and period than a low-metallicity Cepheid of identical mass.