Ascertainment of premature mortality, life expectancy, and biological aging
Death information and date of death were confirmed by reference to the death certificates held by the National Health Service Information Centre for participants in England and Wales and the National Health Service Central Register Scotland for participants from Scotland. The participants were defined as premature mortality if their deaths occurred at ages younger than 75[28]. We calculated the follow up person-years at risk of observation from the date of consenting to join assessment center until the date of loss to follow-up, the date of death, or March 1, 2021, whichever came first. Causes of death were determined by using the International Classification of Diseases Tenth Revision (ICD-10) codes, and its detailed information was described in the Supplementary material.
We used the latest Office for National Statistics life tables rom age 40 to age 100 years to calculate the life expectancy of participants with the distinct number of live births[29,30]. The detailed methods used for estimating the difference in the life expectancy was described in the Supplementary material.
Biological aging was measured from different perspectives, including frailty index (FI), ΔKDM-biological age and Homeostatic disorder (HD). The FI, Δbiological age and HD were previously constructed and validated in the UK Biobank[31]. For each person, FI is calculated as the proportion of health attributes that a person has in a deficit state. FI scores range from 0 (indicating no health deficits) to 1 (indicating every health deficit that was assessed). ΔBiological age represented the value of biological age minus chronological age, representing premature aging[32]. HD represents the degree of variability in individual physiological functions and health parameters, and the HD values are positively correlated with biological aging. Detailed calculations of FI, ΔKDM-biological age and HD are provided in Supplementary material.