The decline in memory and cognition associated with sleep-disordered breathing and long sleep duration was found to be modified by obesity and metabolic disease, according to the results of a study published in Alzheimer’s and Dementia.
Data were sourced from the Study of Latinos – Investigation of Neurocognitive Aging, which recruited Hispanic adults living in 4 cities in the United States between 2008 and 2011. Study participants were assessed for sociodemographic factors, sleep disorders, and neurocognitive status at baseline and at 7-year follow-up.
Study participants had a mean age of 63±8.1 years; 54.8% were women, 83.6% used sleep medication in the past 4 weeks, 14.81% had long sleep duration (>9 hours per night), 6.43% had short sleep duration (<6 hours per night), and 17% had a respiratory event index (REI) ³15. Respiratory events were reported as reduction in airflow of 50% or more lasting at least 10 seconds with desaturations of at least 3%.
Memory performance was poorest among individuals 65 years and older who had REI ³15, long sleep duration, and obesity (delta, -1.58; SE, 0.38; P <.001) or metabolic syndrome (delta, -1.17; SE, 0.38; P =.001). A similar pattern was observed for processing speed among older individuals with high REI scores, long sleep duration, and obesity (delta, -1.23; SE, 0.23; P <.001) or metabolic syndrome (delta, -1.24; SE, 0.25; P <.001). These individuals were also found to experience more pronounced cognitive decline (obesity: delta, -1.00; SE, 0.42; P =.016; metabolic syndrome: delta, -1.00; SE, 0.42; P =.017).
Among individuals aged 45 to 54 years, metabolic syndrome was observed to modify the relationship between sleep duration and REI for global cognition (P <.001), processing speed (P =.003), and memory change (P =.021). Among those 65 years and older, obesity was the modifier for global cognition (P <.001), change in memory (P <.001), and the relationship between sleep duration and memory (P =.001).
A significant modifier for gender was observed for global cognition (P =.010). Women who did not have metabolic syndrome, had long sleep, and REI ³15 exhibited the most pronounced decline in global cognitive function.
This study was limited by using self-reported sleep duration and by the small amount of data available for sleep-disordered breathing.
The study authors concluded that the relationship between sleep-disordered breathing and cognition was modified by obesity and metabolic syndrome. Individuals who were middle-aged and did not have metabolic syndrome as well as older individuals with obesity were found to experience more pronounced cognitive decline.
Kaur SS, Tarraf W, Wu B, et al. Modifying pathways by age and sex for the association between combined sleep disordered breathing and long sleep duration with neurocognitive decline in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). Alzheimers Dement. Published online May 25, 2021. doi:10.1002/alz.12361