As longevity is increasing, the 65-year-old and older population is projected to increase in the next decades, as are the consequences of age-related muscle deterioration on the quality of life. The purpose of this study was to examine the associations of the ACTN3R577X polymorphism with quality of life and muscular strength in an older Spanish population. In total, 281 older adults participated in this study. Anthropometric measurements, chronic diseases, prescribed medications, quality of life, hand grip strength, and physical activity and nutritional status data were collected. ACTN3 R577X genotyping was determined using Taqman probes. Multivariate regression analysis revealed in adjusted model that, in men, the ACTN3 R577X genotype was significantly associated with hand grip strength (HGS), regression coefficient (β) = 1.23, p = 0.008, dimension 1 of the five-dimension questionnaire EuroQoL (EQ-5D, mobility), (β) = -1.44, p = 0.006, and clinical group risk (CGR) category (β) = -1.38, p = 0.006. In women, a marginal association between the ACTN3 R577X genotype and the CGR category was observed, with a regression coefficient of (β) = -0.97, (p = 0.024). Our findings suggest that the ACTN3 R577X genotype may influence the decline in muscle strength and quality of life in older Spanish adult males.

Older adults are at increased risk of several cytochrome P450 (CYP) drug interactions that can result in drug toxicity, reduced pharmacological effect, and adverse drug reactions. This study aimed to assess the prevalence of potential CYP interactions referring to the most clinically relevant drugs and exploring the relationship between them and quality of life and physical performance in Spanish octogenarians. Institutionalized and community-dwelling octogenarians (n = 102) treated at three primary care centers, were recruited by a research nurse. Anthropometric measurements, chronic diseases, prescribed drugs, quality of life, physical performance, mobility skills, hand grip strength and cognitive status data were collected. Potential CYP drug-drug interactions (DDIs) were selected referring to the main CYP implicated in their metabolism. The 72.2% of recruited octogenarians presented potentially inappropriate CYP inhibitor-substrate or CYP inductor-substrate combinations. Analyzing the EuroQol Visual Analogue scale (EQ-VAS) results, patients with a potential CYP DDI perceived worse health status than patients without it (p = 0.004). In addition, patients with a potential CYP DDI presented worse exercise capacity, kinesthetic abilities, or mobility than those who didn't present a potential interaction (p = 0.01, p = 0.047, and p = 0.02, respectively). To investigate and control factors associated with loss of muscle strength and poor quality of life, polypharmacy and DDIs could help institutions in the management of physical frailty.