Familiality and Heritability of Fatigue in an Australian Twin Sample

Is the Pandemic Wearing Us Out? A Cross-Sectional Study of the Prevalence of Fatigue in Adult Twins without Previous SARS-CoV-2 Infection

During the pandemic, mental health was not only impaired in people after a SARS-CoV-2 infection, but also in people without previous infection. This is the first study on twins without prior SARS-CoV-2 infection to estimate the influence of genetic components and shared as well as individual environments on pandemic-associated fatigue. The study sample included 55 monozygotic and 45 dizygotic twin pairs. A total of 34.5% reported an increase in fatigue since the pandemic. A significant correlation was shown between the responses within monozygotic (χ2[1] = 11.14, p = 0.001) and dizygotic pairs (χ2[1] = 18.72, p < 0.001). In all pandemic-associated fatigue dimensions, individual environment (ranging from e2 = 0.64 to e2 = 0.84) and heritability (ranging from h2 = 0.32 to h2 = 1.04) seem to have the highest impact. The number of comorbidities significantly correlated with physical fatigue (Spearman’s ρ = 0.232, p < 0.001) and psychological impairment due to pandemic measures with the total fatigue score (Spearman’s ρ = 0.243, p < 0.001). However, calculated ANCOVAs with these significant correlations as covariates showed no significant influence on the mean values of the respective fatigue dimensions. Susceptibility to pandemic-associated fatigue may be genetically and environmentally determined, while intensity is also influenced by individual components. The prevalence of fatigue is high even in individuals without prior SARS-CoV-2 infection. Future mental health prevention and intervention programs should be implemented to alleviate the impact of the pandemic on the global population.

Epidemiology of Perceived Physical Fatigability in Older Adults: The Long Life Family Study

BACKGROUND

Fatigability is a construct that measures whole-body tiredness anchored to activities of a fixed intensity and duration; little is known about its epidemiology and heritability.

METHODS

Two generations of family members enriched for exceptional longevity and their spouses were enrolled (2006-2009) in the Long Life Family Study (LLFS). At Visit 2 (2014-2017, N = 2,355) perceived physical fatigability was measured using the 10-item self-administered Pittsburgh Fatigability Scale (PFS), along with demographic, medical, behavioral, physical, and cognitive risk factors.

RESULTS

Residual genetic heritability of fatigability was 0.263 (p = 6.6 × 10-9) after adjustment for age, sex, and field center. PFS physical scores (mean ± SD) and higher physical fatigability prevalence (% PFS ≥ 15) were greater with each age strata: 60-69 (n = 1,009, 11.0 ± 7.6, 28%), 70-79 (n = 847, 12.5 ± 8.1, 37%), 80-89 (n = 253, 19.3 ± 9.9, 65.2%), and 90-108 (n = 266, 28.6 ± 9.8, 89.5%), p < .0001, adjusted for sex, field center, and family relatedness. Women had a higher prevalence of perceived physical fatigability compared to men, with the largest difference in the 80-89 age strata, 74.8% versus 53.5%, p < .0001. Those with greater body mass index, worse physical and cognitive function, and lower physical activity had significantly higher perceived physical fatigability.

CONCLUSIONS

Perceived physical fatigability is highly prevalent in older adults and strongly associated with age. The family design of LLFS allowed us to estimate the genetic heritability of perceived physical fatigability. Identifying risk factors associated with higher perceived physical fatigability can inform the development of targeted interventions for those most at risk, including older women, older adults with depression, and those who are less physically active.