The Protective Effect of Familial Longevity Persists After Age 100: Findings From the Danish National Registers.

BACKGROUND: A recent study suggested that the protective effect of familial longevity becomes negligible for centenarians. However, the authors assessed the dependence on familial longevity in centenarians by comparing centenarians with 1 parent surviving to age 80+ to centenarians whose same-sexed parent did not survive to age 80. Here we test whether the protective effect of familial longevity persists after age 100 using more restrictive definitions of long-lived families. METHODS: Long-lived sibships were identified through 3 nationwide, consecutive studies in Denmark, including families with either at least 2 siblings aged 90+ or a Family Longevity Selection Score (FLoSS) above 7. Long-lived siblings enrolled in these studies and who reached age 100 were included. For each sibling, 5 controls matched on sex and year of birth were randomly selected among centenarians in the Danish population. Survival time from age 100 was described with Kaplan-Meier curves for siblings and controls separately. Survival analyses were performed using stratified Cox proportional hazards models. RESULTS: A total of 340 individuals from long-lived sibships who survived to age 100 and 1 700 controls were included. Among the long-lived siblings and controls, 1 650 (81%) were women. The results showed that long-lived siblings presented better overall survival after age 100 than sporadic long-livers (hazard ratio [HR]  = 0.80, 95% confidence interval [CI]  = 0.71-0.91), with even lower estimate (HR = 0.65, 95% CI = 0.50-0.85) if familial longevity was defined by FLoSS. CONCLUSIONS: The present study, with virtually no loss to follow-up, demonstrated a persistence of protective effect of familial longevity after age 100.