Tea drinking and cognitive function in oldest-old Chinese

Abstract

Objective: We examined the longitudinal association between tea drinking frequency and cognitive function in a large sample of oldest-old Chinese.

Design: population-based longitudinal cohort study.

Setting: The Chinese Longitudinal Healthy Longevity Survey (CLHLS).

Participants: 7139 participants aged 80 to 115 (mean age 91.4 years) who provided complete data at baseline (year 1998).

Measurements: Current frequency of tea drinking and past frequency at age 60 were ascertained at baseline, and baseline and follow-up cognitive assessments were performed in the years 1998 (n=7139), 2000 (n=4081), 2002 (n=2288) and 2005 (n=913) respectively. Verbal fluency test was used as measure of cognitive function.

Results: Tea drinking was associated at baseline with higher mean (SD) verbal fluency scores: daily=10.7 (6.6), occasional=9.2 (5.8), non-drinker=9.0 (5.5). In linear mixed effects model that adjusted for age, gender, years of schooling, physical exercise and activities score, the regression coefficient for daily drinking (at age 60) and occasional drinking was 0.72 (P<0.0001) and 0.41(P=0.01) respectively. Tea drinkers had higher verbal fluency scores throughout the follow-up period but concurrently had a steeper slope of cognitive decline as compared with non-drinkers (coefficient for the interaction term Time*Daily drinking= -0.12, P=0.02; "Time" was defined as the time interval from baseline to follow-up assessments in years). Similar results were found for current tea drinking status at study baseline year (1998) as predictor variable.

Conclusion: Regular tea drinking is associated with better cognitive function in oldest-old Chinese.

Figure 1

The Decline in verbal fluency scores during follow-up period according to tea drinking frequency at age 60

Figure 2

The Decline in verbal fluency scores during follow-up period according to tea drinking frequency in year 1998