Age Factors Aged Blepharoptosis--classification Cohort Studies Female Genetic Predisposition to Disease--epidemiology Genome-Wide Association Study Genotype Health Behavior Homeodomain Proteins--genetics Humans Male Middle Aged Netherlands--epidemiology Polymorphism, Single Nucleotide Repressor Proteins--genetics Risk Factors Sex Factors Skin Aging Skin Pigmentation Smoking--epidemiology Sunlight Twin Studies as Topic United Kingdom--epidemiology