The influence of nutritional determinants on ageing

Resumen

The ageing of the population has become a major significant concern and a global public health challenge. Most of the disease burden in the elderly is related to chronic diseases that could be prevented, delayed, or even reversed by focusing on healthy-related behaviours and lifestyle. Even in the very elderly population, an improvement in physical activity, the maintenance of adequate nutrition, and the removal of unhealthy behaviours can have major benefits on well-being. An important example of a syndrome that could be reverted and is associated with an increased risk of hospitalization, disability, morbidity, and mortality, is frailty. Likewise, falling is the most frequent cause of death related to unintentional injury and the six leading cause of death in people aged 65 years or older. However, nutritional determinants associated with frailty and falls have been poorly identified. Therefore, the main objective of this thesis is to address the influence of some of these nutritional determinants on ageing. Data were taken from the Seniors-ENRICA (Study on Nutrition and Cardiovascular risk factors in Spain) cohort, which was established in 2008-2010 with 2,614 noninstitutionalized aged 60 years and older in Spain. At baseline, a computer-assisted phone interview was performed to collect data on socio-demographic factors, health behaviours and morbidity. Then, two home visits were conducted to obtain a dietary history, perform a physical exam, and collect biological samples; the average time between the phone interview and the second home visit was 2 weeks. For cognitively impaired subjects, data were collected with the help of a proxy. Participants were followed-up until 2012, when a second wave of data collection was performed, including related frailty and falls information. This thesis first evaluates the association of protein and other macronutrient intake with incident frailty in noninstitutionalized older men and women from Spain, using logistic regression models. Then, it assesses the prospective association of protein intake with the risk of falls in the same cohort, and stratifies the analysis according to unintentional weight loss. Logistic models are used to assess the risk of falls. Finally, it investigates the relationship between ultra-processed food intake and incident frailty in the same cohort, using logistic regression models with adjustment for the main confounders. During a mean follow-up of 3.5 years, 132 participants with incident frailty were identified. The odds ratios (ORs) and the 95% confidence interval (95% CI) of frailty across increasing quartiles of total protein intake were 1.00, 0.55 (0.32-0.93), 0.45 (0.26-0.78), and 0.41 (0.23-0.72); p for trend = 0.001. The corresponding figures for animal protein intake were 1.00, 0.68 (0.40-1.17), 0.56 (0.32-0.97), and 0.48 (0.26-0.87); p for trend = 0.011. When MUFAs were considered, the results were 1.00, 0.66 (0.37-1.20), 0.54 (0.28-1.02), and 0.50 (0.26-0.96); p for trend = 0.38. No association was found between intake of vegetable protein, saturated fats (SFAs), long-chain ω-3 fatty acids, α-linolenic acid (ALA), linoleic acid (LA), simple sugars, or polysaccharides and the risk of frailty. During the same period, a total of 522 participants (21.2%) experienced at least one fall. The ORs (95% CI) of falls for the three increasing tertiles of total protein intake were 1.00, 0.86 (0.66-1.11), and 0.93 (0.70-1.24); p for trend = 0.14. However, a statistically significant interaction with unintentional weight loss was observed for the association between protein intake and the risk of falls; p for interaction = 0.004. Among 163 participants (6.6%) who experienced an unintentional weight loss of 4.5 kg or more in the preceding year, the ORs (95% CI) of falls for the three increasing tertiles of total protein intake were 1.00, 0.68 (0.21-2.23), and 0.23 (0.05-1.08); p for trend = 0.01. Regarding ultra-processed food consumption, expressed as percentage of total energy intake, the ORs (95% CI) for frailty across increasing quartiles were 1.00, 1.52 (0.78-2.96), 2.98 (1.62-5.50), and 3.67 (2.00-6.73); p for trend = <0.001. Results were similar when food consumption was expressed as gram per day/kg of body weight (g/kg). A greater intake of ultra-processed foods from non-alcoholic beverages (instant coffee and cocoa, packaged juices, and other non-alcoholic drinks, excluding soft drinks), yogurts and fermented milks (natural and non-sugary yogurts are not included in this category), as well as cakes and pastries was also significantly related to incident frailty. These results provide novel evidence about the influence of the intake of total protein, animal protein, and MUFAs on incident frailty and conclude that promoting the intake of these nutrients might reduce frailty. Additionally, regarding the association of protein intake and falls, high total protein intake shows to confer substantial benefits to participants who experienced an unintentional weight loss of 4.5 kg or more in the preceding year. Finally, the findings add evidence for the restriction of ultra-processed foods, and the promotion of fresh or minimally processed foods in the older adult population.