By analysing a survey of over 13,000 elderly participants living in China, a team of researchers led by Associate Professor Feng Qiushi from NUS Sociology and his colleague Associative Professor Shen Ke from Fudan University have found an association between consistent and frequent tea-drinking and significantly less depressive symptoms in Chinese older adults.
Their results were published in the journal BMC Geriatrics on 4 September 2019.
Depression, as one of the most common mental disorders for the elderly, often causes great suffering in later life, with ‘major depressive disorder’ now affecting about 7% of adults aged over 60 worldwide.
Hence, a growing body of research has been exploring risk factors for elderly depression, ranging from biomarkers, behaviour characteristics, socioeconomic status, family structure, living arrangement, to community environment.
Amongst these factors, the consumption of tea, one of the most popular non-alcoholic beverages in the world, is drawing the attention of researchers.
An example of this research, and an inspiration for this study, was the earlier work of Assistant Professor Feng Lei at NUS Psychological Medicine, who systematically investigated the positive effect of tea-drinking on brain function, mental health and mortality in old age.
The potential benefit of tea over mental health
One key debate on the benefit of tea over mental health is whether the potential impact comes from the biochemical components of tea or the social context of tea drinking. Hence, in their study, Assoc Prof Feng and his team controlled for covariates that could have significant associations with elderly depression.
They looked at nationwide data from China by utilising the Chinese Longitudinal Healthy Longevity Survey (CLHLS) ranging from 2005-2014.
The factors they took into account included: age, gender, residence, education, marital status and pension status. They also considered lifestyle and health conditions when calculating their results, including whether the seniors were currently smoking, whether they were currently drinking alcohol, activities of daily living and cognitive function. Lastly, they examined how social engagement could affect the results, which included activities such as playing cards or mahjong, participating in community activities and travel.
The link between drinking tea and depression
In all cases measured for, consistent daily drinking of tea remained a significant preventive factor against depressive symptoms. Urban living, being educated and married, economic adequacy, better health and engagement in social activities were also related to less depressive symptoms.
When dividing the groups by age and gender, it was found that the association between tea-drinking and less depressive symptoms was significant only for males between 65-79 years old. “It is likely that the benefit of tea-drinking is more evident for the early stage of heath deterioration. More studies are surely needed in regard to this issue,” Assoc Prof Feng explained.
The study also found that the mean age, proportions of men and urban residents, and proportions of being educated, married and receiving pension, were also relatively higher among those who frequently and consistently consume tea. Meanwhile, tea drinkers tended to smoke and drink, but had better physical and cognitive functioning. And they were more socially involved.
This correlation between drinking tea and depressive symptoms has yet to be proven causative, but commenting on these initial results, Assoc Prof Feng said, “Consistent and frequent tea-drinking may effectively reduce the risk of depressive symptoms for the Chinese elderly. The promotion of the traditional lifestyle of tea drinking could be a cost-effective way towards healthy aging for China.”
This association is applicable to Singaporeans too. In June 2017, Asst Prof Feng Lei's team published results in The Journal of Prevention of Alzheimer's Disease specifically examining Singaporeans using data from the Diet and Healthy Aging Study (DaHA). The results clearly revealed that long-term tea consumption was associated with reduced depressive and anxiety symptoms among Singaporeans. These new results from Assoc Prof Feng and his team add further credence to these earlier findings.
Looking to the future, Assoc Prof Feng and his team are now collecting new data from the CLHLS about tea-drinking. “This new round of data collection has distinguished different types of tea such as green tea, black tea, and oolong tea, so that we could see which type of tea really works for alleviating depressive symptoms,” he said.