This study examined the relationship between diet and risk of death in elderly Chinese, using 10 years of data from a large longitudinal health survey. Cox proportional hazards regressions were used to estimate the effects of dietary habits and lifestyle factors on the risk of mortality, adjusting for various individual characteristics.
Consistent with previous findings, our study showed that the intake of fruit and vegetables was an important factor to reduce the risk of death in the elderly. However, different frequencies of fruit consumption were associated with different levels of mortality risk reduction. Contrary to the idea that the more fruit you eat, the better your diet, the results showed that eating fruit occasionally was associated with a 3% lower risk of death than eating it almost every day. Although fruits and vegetables were good for the health of the elderly, we recommend that they should also be consumed in moderation. While ensuring the needs of the body, they can maximize the benefits of fruits and vegetables to the body.
Fish consumption was associated with a reduction in all-cause mortality in the elderly. Fish was the most common dietary source of long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs), which had been demonstrated to have antiatherosclerotic and antithrombotic effects[12, 13]. Recently, the Vitamins and Lifestyle Study (VITAL Study) reported that higher intake of fish was significantly associated with a lower risk of all-cause mortality. What is the optimal intake of fish? Zhao’s study showed that consumption of 60 g of fish per day was associated with a 12% reduction (RR = 0.88, 95% CI: 0.83, 0.93) in risk of total death, compared with never consumers. We had also found the same situation in the elderly population in China. Compared with people who never eat fish, the elderly who consume fish almost every day can reduce the risk of death by 10.8%. Different regions in China had different dietary patterns. People in coastal areas ate more fish, but people in northwest China ate less fish due to environmental factors, which was often related to their income level. As fish was an indispensable part of a healthy diet pattern, people in arid northwest China should pay more attention to the consumption of fish in their diet to ensure the health needs of the special group of elderly people.
Drinking tea was a traditional habit of the Chinese people, especially among the elderly. Previous studies had shown that frequent tea consumption was associated with reduced mortality in Chinese over 80 years of age, and tea had a strong beneficial effect on survival and longevity in later life. Our research further confirmed the negative correlation between frequent tea drinking and all-cause mortality in the elderly. However, we found that occasional tea consumption was associated with an increased risk of death in the elderly, which indicated that daily tea consumption has potential public health benefits, and long-term regular tea drinking should be developed to improve health and reduce the risk of death. Consumption of nut products was associated with a reduced risk of mortality. A systematic review of nuts and human health suggested that nut intake could prevent and/or treat some chronic disease related risk factors, such as changes in glycemic and lipid metabolism, oxidative stress, and inflammation.
In the past few decades, Consumption of staple food had shifted from traditional coarse grains to refined grains in China. The study found that rice, wheat, corn, and a mixture of rice and wheat as the staple food had different effects on mortality risk reduction compared with other types of staple foods, while a regional study in China demonstrated a negative correlation between rice intake and cardiovascular mortality. Wheat-based foods provide the human diet with a range of essential and beneficial ingredients, including protein, B vitamins, dietary fibre and phytochemicals. Staple food was the source of energy and carbohydrates in our daily diet, and too high or too low carbohydrate intake was not conducive to health. A prospective study and meta-analysis found that both high and low dietary carbohydrate intakes were associated with increased mortality, with the lowest risk of death when carbohydrate intakes ranged from 50–55%. In addition, we also found that in the full model, compared with rice as a staple food, the risk of mortality from a mixture of rice and wheat as a staple food can be reduced by 3.7%. Therefore, while paying attention to the intake of staple food in the elderly, we should also pay attention to the diversification of staple food intake, and try to avoid long-term consumption of a single staple food.
Cooking oil was associated with an increase in mortality. Unlike Western countries, lard was a commonly used animal edible oil in China. It was often used in a high-fat diet, which can induce obesity and diabetic phenotypes in rodents. In China, 80 percent of vegetable oil was fried, but changes that may be harmful to health may occur during frying[23, 24]. In view of the great harm of cooking oil to human health, and the metabolism of the elderly was slow, easy to indigestion and other problems, we suggested that in the process of nutrition publicity and education, it should be emphasized that the elderly should eat less or do not eat Fried food, and should pay attention to cooking with less oil in their daily diet.
In this sample of the elderly Chinese, regular intakes of salt-preserved vegetables and garlic were not found to be associated with mortality. A study on diet and self-rated health among older Chinese also showed that consumption of salt-preserved vegetables and garlic were not associated with self-rated health. Weight gain was associated with a lower risk of death, but the reduction was not significant for each unit of weight gain. In China, nearly half of the elderly were at risk of malnutrition. The elderly with higher body weight may be in good physical condition, which was consistent with previous studies. Low frequency of activity was associated with an increased risk of death in older adults compared to high frequency of activity. Fishman and colleagues3 observed that higher volumes of total physical activity were associated with lower mortality, especially, greater light activity is also associated with lower mortality independent of MVPA. In future public health education, we encouraged older people to participate more in low-intensity activities and to be less sedentary. We found that women had a lower risk of mortality than men. Married persons had better health and mortality outcomes than unmarried persons.
The advantages of this study include a large national sample, and a comprehensive dietary factor. It should be noted that some limitations of the study. First, the measurement of dietary intake was rough. Based on Shi’s study, we included the frequency of vegetables and fruit intake of “almost every day except winter” into “almost every day”, forming three categories, “almost every day”, “occasionally”, “rarely or never”. Admittedly, this categorization was crude and subjective, however, due to the question wording across CLHLS survey waves, such a classification of dietary intake frequency tends to be a relatively sensible choice. Second, the lack of detailed dietary information in this study limited our ability to comprehensively adjust for total energy intake and dietary intake. Third, due to smoking, drinking, and exercising were based on the current status of the problem, and it did not include smoking, drinking, exercise frequency and past history, the study was relatively incomplete in assessing the impact of lifestyle factors on the risk of mortality. Finally, there was no relevant height data, body mass index (BMI) can’t be calculated and the classification was not performed. Therefore, in future studies, in order to more comprehensively analysis the impact of weight on the risk of mortality, weight can be divided into groups and converted into categorical variables, or put into the model in the form of BMI.
This study assessed the relationship between dietary habits, lifestyle and mortality risk in the Chinese population aged 65 years and older. Compared to those who rarely/never consumed fruit, vegetables, fish, tea and nut products, participants consuming such products almost every day had a lower risk of mortality during follow-up. Cooking oil was associated with increased mortality, and regular participation in activities would reduce the risk of mortality and be good for the health of the elderly. The impact of dietary habits on the risk of mortality of the elderly differed by gender to some extent. In future studies, the impacts of different dietary intake amount on the health and mortality of the elderly can be further analyzed to provide a basis for determining the daily dietary intake amount suitable for the elderly group, meeting nutritional requirements and improving health level. In addition, while advocating a reasonable diet, the elderly should reduce the frequency of using cooking oil and the intake of Fried food.