It is possible obtain accurate estimates of age from DNA methylation profiles derived from human tissues. When estimates over-estimate chronological age, we say that the corresponding individuals have accelerated DNA methylation age. Recent publications have shown that these individuals tend to have poor health compared to others. What we do not know is how stable age acceleration is throughout life. We would like to use the longitudinal DNA methylation profiles in ALSPAC to determine how often individuals with accelerated age at one time point are also accelerated at other time points.