Full Length ArticleCoffee and tea drinking in relation to risk of hip fracture in the Singapore Chinese Health Study
Introduction
Coffee and tea are among the most widely consumed beverages in the world, and have been studied extensively on health impacts, including osteoporosis and related fractures [1,2]. However, the effects of coffee and tea on bone health are mixed in experimental and observational studies. This could partially be due to drinking habits and the complexity of chemical constituents in tea and coffee.
Coffee is the major source of caffeine and contains other non-caffeine compounds such as cafestol, chlorogenic acid, caffeic acid and trigonelline [1,3]. In experimental settings, caffeine at a high dosage suppressed osteogenesis [4], increased osteoblastic apoptosis [5], and induced osteoclastic formation and differentiation [6] in vitro. In animal models, high caffeine intake inhibited bone growth, decreased bone mineral density [[5], [6], [7]], and interrupted bone healing [8]. By contrast, caffeine at low to moderate doses enhanced osteogenesis [4], and increased bone mass and strength in oophorectomized rats [9]. Non-caffeine compounds found in coffee, such as caffeic acid, chlorogenic acid [10] or trigonelline [3], on the other hand, exerted unfavorable effects in the skeletons in ovariectomized rats. Hence, it is possible that the effect of coffee consumption on bone health may depend on dosage and the composition of caffeine and non-caffeinated compounds in coffee. Tea is an important source of polyphenols and has a considerably lower level of caffeine than coffee based on volume. Polyphenols from black tea (theaflavin-3, 3′-digallate) and green tea (epigallocatechin-3-gallate) inhibited osteoclastic formation and differentiation [11], reduced bone loss [12,13] and improved microarchitecture [12] in ovariectomized rats.
In observational studies, no significant results have been found between consumption of coffee or tea and fracture risk, where the pooled relative risk in meta-analyses comparing the highest to the lowest category of coffee intake ranged from 0.94 to 1.30 for hip fractures [14,15] and fractures in general [16]. Additionally, the effect of a high intake of caffeine on osteoporosis may not be harmful, particularly among those with sufficient calcium intake [17]. Further, the amount used to define coffee intake levels varied among studies, which may contribute to high heterogeneity (all I2 > 56%) and inconsistent effect estimates [[14], [15], [16]]. Stratified analysis by gender in these meta-analyses have suggested a reduced risk in men but an increased risk in women for the association with coffee consumption [[14], [15], [16]]. Data in these meta-analyses were further re-analyzed by Poole and colleagues and confirmed the inconsistent associations and a sex-specific difference between coffee consumption and fracture risks [17]. Similarly, inconsistent results were reported for the association with tea [2,14].
The results from previous observational studies are primarily conducted in Caucasian populations in Europe or North America [16,18]. To our knowledge, there is only one Asian study of a case-control study among Japanese men and women, suggesting that those who consumed three or more cups of coffee per day had a higher fracture risk [19]. In the context of a relatively lower consumption of coffee or caffeine, and a rise in hip fracture incidence in Asian populations [19], we comprehensively examined the longitudinal relationship between consumption of coffee and tea, as well as estimated caffeine intake, and the risk of hip fracture in a large Asian cohort. We further tested for evidence of a potential non-linear relation as suggested in experimental findings. We hypothesized that a high intake of coffee/caffeine might increase the risk of hip fractures while a low intake might reduce the risk.
Section snippets
Study population
The current study was conducted in the Singapore Chinese Health Study, a population-based prospective cohort of 63,257 men (n = 27,959) and women (n = 35,298), aged 45–74 years at recruitment between April 1993 and December 1998. The study participants were restricted to two major dialect groups in Singapore, the Hokkiens and the Cantonese, who originated from Fujian and Guangdong provinces in Southern China, respectively. All of our study participants were recruited from residents living in
Results
After a mean (standard deviation, SD) follow-up of 16.7 (5.2) years among a total of 63,154 participants, 2502 incident hip fracture cases were identified through the nationwide hospital linkage. The mean age (SD) at hip fracture was 79.4 (6.9) years. Women accounted for 72.7% of all hip fractures. The age-standardized incidence rate of hip fractures was 294 per 100,000 person-years for women and 157 per 100,000 person-years for men. About 70% of our cohort participants were daily coffee
Discussion
In this large prospective cohort of middle-aged to elderly Singapore Chinese, compared to those who drank <1 cup of coffee per week, we found that consumption of 4 or more cups of coffee per day was associated with a higher risk of hip fracture in both men and women. A possible J-shaped non-linear relationship between coffee or caffeine intake and risk of hip fracture may exist among postmenopausal women, with the lowest risk at drinking 2–3 cups of coffee per day or caffeine intake of
Funding
This study was supported by the National Medical Research Council, Singapore (NMRC/EDG/0011/2007) and U.S. NIH grants RO1 CA144034 and UM1 CA182876.
Disclosure
All authors state that they have no conflict of interest. W-P Koh is supported by the National Medical Research Council, Singapore (NMRC/CSA/0055/2013).
Acknowledgments
We thank Siew-Hong Low of the National University of Singapore for supervising the fieldwork and Renwei Wang for the maintenance of the database in the Singapore Chinese Health Study. We also thank the Ministry of Health in Singapore for assistance with the identification of hip fracture cases and mortality via database linkages. Finally, we thank the founding principal investigator of the Singapore Chinese Health Study, Mimi C. Yu.
Author's contributions
Z.D. and W.-P.K. designed the study, analyzed the data, and drafted the manuscript; W.-P.K., L.-W.A, and J.-M.Y. conducted the study and collected the data; Z.D., J.-M.Y., and W.-P.K. interpreted the data, and A.J. further updated the linkage, and A.J. and A.S. analyzed the data under W.-P.K.'s supervision. W.-P.K. took the responsibility for the integrity of the data analysis. All authors read and approved the final version of the paper.
References (36)
- et al.
Tea and bone health: steps forward in translational nutrition
Am. J. Clin. Nutr.
(Dec 2013) - et al.
Effects of caffeine and exercise on the development of bone: a densitometric and histomorphometric study in young Wistar rats
Bone
(Jan 2002) - et al.
The effects of caffeine administration on the early stage of bone healing and bone density A histometric study in rats
Arch. Oral Biol.
(Aug 2009) - et al.
Tea polyphenols inhibit rat osteoclast formation and differentiation
J. Pharmacol. Sci.
(2012) - et al.
Coffee consumption and risk of fractures: a systematic review and dose-response meta-analysis
Bone
(June 2014) - et al.
Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children
Food Chem. Toxicol.
(Nov 2017) - et al.
Case-control study of risk factors for hip fractures in the Japanese elderly by a Mediterranean Osteoporosis Study (MEDOS) questionnaire
Bone
(Nov 1997) - et al.
Adherence to a vegetable-fruit-soy dietary pattern or the Alternative Healthy Eating Index is associated with lower hip fracture risk among Singapore Chinese
J. Nutr.
(Apr 2014) - et al.
Caffeine, moderate alcohol intake, and risk of fractures of the hip and forearm in middle-aged women
Am. J. Clin. Nutr.
(Jul 1991) - et al.
Caffeine decreases vitamin D receptor protein expression and 1,25(OH)2D3 stimulated alkaline phosphatase activity in human osteoblast cells
J. Steroid. Biochem. Mol. Biol.
(Mar 2007)