Background: Cognitive screening tools, such as the MoCA and TICS-M, are commonly used in patients with TIA and stroke, both in research studies and in clinical practice. However, short-term changes could be influenced by seasonal variation in performance, with impaired performance in Winter/Spring (Jan-June) months reported on more detailed cognitive testing.  We determined whether time of year affects the results of more limited telephone cognitive testing in older individuals at risk of stroke.

Methods: Older subjects (≥ 70 years) with hypertension enrolled in an ongoing trial of blood pressure lowering completed serial telephone cognitive assessments (T-MoCA; TICS-M) six months apart. The difference between baseline and six month scores was compared for baseline assessments in Winter/Spring (Jan-June) versus Summer/Autumn (July-Dec) after adjustment for age, sex and level of education.

Results: Among 711 (78.0%) participants who had baseline and 6 month assessments in different seasons, a lower baseline cognitive score was associated with male gender, low education and increasing age (T-MOCA – all p<0.001, TICS-M – all p<0.001). On repeat testing after 6 months subjects tested at baseline in Winter/Spring showed improvement on testing in Summer/Autumn (mean difference in score: T-MOCA +0.95; TICS-M +0.70), whereas no significant improvement was seen in those first tested in Summer/Autumn (T-MOCA +0.56; TICS-M +0.13): difference in change (T-MoCA – p=0.007; TICS-M – p=0.037).  

Conclusions: Season does appear to affect the results of telephone cognitive screening in  older subjects. Trials and other studies involving repeat testing should ensure that this potential bias is considered in design and analysis.

DOES SEASON AFFECT TELEPHONE COGNITIVE SCREENING PERFORMANCE IN OLDER SUBJECTS?