Untreated OSA, Arterial Hypertension May Contribute to Cognitive Decline

Arterial hypertension (AH) and obstructive sleep apnea (OSA) seem to be risk factors in common neurocognitive disorder (NCD), but cognitive decline can be mitigated by treating these risk factors, according to a study published in Scientific Reports.

This study was conducted because multiple risk factors, including AH and OSA, that contribute to the various types of dementia have been recognized in previous studies, and studies that observed AH did not investigate long-term effects or separate it from other risk factors. Studies involving OSA as a risk factor failed to include participants with all stages of NCD.

Researchers attempted to investigate the effect of AH and OSA on cognitive course in the NCD cohort RIFADE (RIsk FActors of DEmentia), which enrolled patients in the lower Rhine area of Germany who had NCD because of Alzheimer disease (AD), vascular NCD, and mixed NCD (AD + vNCD = mNCD).

There is growing evidence that certain risk factors are involved in AD and vascular dementia, the 2 most common types of dementia. Vascular risk factors, hypacusis, and more could contribute to the development of up to 40% of dementias.

“This is of particular interest for [AD], where successful treatments improving or even stabilizing cognitive outcomes for time periods of years have so far been lacking. However, correction or elimination of a suspected pathological factor does not necessarily lead to successful treatment, which has been revealed by numerous attempts to address cellular pathology,” the researchers wrote.

A total of 126 subjects were screened for AH and OSA. Repeated cognitive measurements were carried out with the DemTect measurement system as the primary outcome and the clock drawing test as the secondary outcome measure.

A total of 90 patients had AH (71.4%) and 40 patients had OSA (31.7%). Risk factor status had a significant effect on cognitive outcome in models with RF as single factors (AH: P = .027; OSA: P < .001), a 2-factor analysis with AH x OSA (HA as main factor P = .027), and a model including the 3 factors, AH x OSA x diagnosis (P = .038). Comparably, a 3-factor model was significant for the clock-drawing test, whereas single-factor models stayed insignificant.

Researchers wrote that the treatment of AH could be improved beyond that achieved in this cohort. They also stated that identifying and treating OSA will improve treatment effectiveness in hypertension and lead to a higher chance of favorable cognitive outcomes. Blood pressure should be more frequently measured in subjects with cognitive complaints, not just to diagnose hypertension, but also to monitor its correction status in order to avoid negative cognitive effects.

Regarding OSA, they wrote, “the current study is in accordance with findings of positive cognitive effects of OSA treatment in patients with NCD and is the first report on treated and untreated OSA patients in all stages of pre-existing [NCD], showing favorable cognitive effects of treatment on the long-term in a substantial proportion of OSA patients.”

Conversely, the researchers said that a subgroup of patients with OSA might have adapted to apnea-related hypoxia and other pathological events associated with OSA. Because a high proportion of patients do not tolerate continuous positive airway pressure treatment, a search for biomarkers is needed to estimate cognitive outcomes in untreated OSA and the urgency of treatment at an individual level. Obesity reduction is also recommended to help address other risk factors such as hypertension.

They also said that treating AH might be a preventive strategy to avoid later AD, supported by a recent meta-analysis. Additionally, it was found that untreated AH resulted in worse cognitive outcomes in OSA among all OSA states, but more studies are needed.

Some limitations included the small number of enrolled patients.

“Patients with AD or vascular-/ mixed-NCD should be screened for hypertension and obstructive sleep apnea and treated for these factors as far as possible,” the researchers concluded.

Reference

Kujovic M, Lipka T, Zalman M, Baumann L, Jänner M, Baumann B. Treatment of hypertension and obstructive sleep apnea counteracts cognitive decline in common neurocognitive disorders in diagnosis-related patterns. Sci Rep. Published online May 9, 2023. doi:10.1038/s41598-023-33701-2