Biological Aging

Aging and chronic diseases

The aging of humanity, especially in developed countries, and the chronic diseases of older people pose huge challenges to medical care. The current model of medical research and practice features investigation and treatment of specific diseases. Yet, recent research suggests that biological aging underlies the development of most chronic diseases. A recent commentary in the widely respected journal, Cell, proposed a substantial increase in aging research. Slowing the rate of human aging may simultaneously reduce the incidence and severity of chronic diseases and extend the healthspan of seniors. A reduced rate of aging may help avoid or at least postpone chronic diseases, help older people improve their health and quality of life, and reduce medical care costs.

Geroscience aims to reveal the biological mechanisms of aging. Thus, aging research has the potential to understand and develop therapies that will prevent or ameliorate chronic diseases more effectively than research on specific chronic diseases. A key goal of aging research is delaying the onset of chronic diseases more than increasing longevity. In other words, expanding human healthspan, such that older people spend more of their later years in a healthy state. A number of potential anti-aging factors have been identified including the healthy lifestyle choices of Keep Moving, Eat Better, and Defuse Chronic Stress. It appears that people who embrace these healthy choices, ideally starting at an early age and continuing until death, can expect to increase their Quality of Lifespan, thereby avoiding or postponing chronic diseases until the last few years of life.

Physical activity and longer telomeres

Telomeres form protective caps on the ends of chromosomes, thereby helping preserving their information-carrying capacity. Over time, telomeres decrease in length, finally to the point that further cell division stops and the affected cells die. Telomere length is a marker of biological aging. A recent review of 20 longitudinal studies suggests that healthy living, in particular increased physical activity, predicts a slower rate of telomere length decline of white blood cells and muscle cells. Shorter telomere length also predicts increased risk of cancer, cardiovascular disease, obesity, diabetes, chronic pain, and stress.

The mechanisms by which physical activity might slow the rate of telomere length decline and slow the rate of aging remain unclear, but might include increased telomerase activity, lower oxidative stress and inflammation, and more recruitment of satellite cells. Telomerase is an enzyme that builds longer telomeres. Satellite cells are precursors of skeletal muscle cells that produce muscle cells after muscle injury. Physical activity promotes skeletal cells and may promote muscle cell maintenance with age. Thus, physical activity might have both protective and restorative effects that slow aging in middle-aged and older adults

Increased physical activity predicts longer white blood cell telomere length and, hence, slower rate of biological aging. Do demographic and lifestyle factors affect the relationship? Researchers used cross-sectional data from 5,823 adults from the National Health and Nutrition Examination Survey (NHANES 1999-2002) to address this question. Participants self-reported frequency, intensity, and duration of participation in 62 physical activities. Overall, telomeres shortened significantly by 15.6 DNA base pairs for each year increase in chronological age even after adjusting for demographic and lifestyle factors. Participants in the high physical activity group had an average 140 more telomere DNA base pairs than sedentary participants. This difference translated into a biological aging advantage of 9 years (140 base pairs÷15.6) compared to sedentary adults. Physical activity significantly and meaningfully predicted greater telomere length in US men and women.

Huge differences in the Pace of Aging

We humans age at different rates, but the underlying reasons remain murky. An international team of researchers used a unique dataset consisting of repeated measures of 19 biomarkers for 1,037 persons born in Dunedin, New Zealand, over the same 1-month period. Biomarker data showed the status of the cardiovascular, metabolic, renal, immune, dental, and pulmonary systems of the participants at ages 26, 32, 38, and 45 years. The age-related decline in these systems was indexed as the Pace of Aging, with larger values reflecting greater biological age and faster aging. The current study updated a previous paper that used data through age 38.

The Pace of Aging varied six-fold across participants, ranging from 0.40 biological years per chronological year to 2.44 biological years per chronological year at mid-life. Faster biological aging predicted thinner brain cortical thickness and smaller total cortical surface area plus smaller hippocampus volume as determined from imaging. Faster biological aging predicted lower intelligence quotient (IQ) and more cognitive decline at age 45, plus poorer cognitive functioning across several domains. Faster biological aging also predicted decreased sensory-motor capabilities including weaker grip strength, slower gait speed, slower repeated rising from a chair, and impaired hearing. Faster biological aging predicted increased negative attitudes toward aging, which was verified by knowledgeable informants.

These associations with the Pace of Aging were not related to overweight or smoking or common age-related disease or social class or sex. Faster biological aging across the first half of the lifespan predicts increased physical and mental impairment at mid-life. On the bright side, the wide variation in the Pace of Aging suggests that at least some of it might be explained by differential adoption of healthy lifestyle choices. For example, the biomarkers that showed the greatest increase between age 28 and 45 included waist-to-hip ratio, lung function, HbA1c (a measure of average blood sugar over 2-3 months). Adopting the healthy lifestyle choices of keep Moving and Eat Better would likely maintain a healthy body shape and weight over time and slow biological aging.

Evidence accumulates

A new systemic review of 43 studies of adult participants examined the effect of physical activity on telomere length and telomerase activity. Overall, regular physical activity at moderate or vigorous intensity seems to maintain telomere length. Many factors affect telomere length and its role in biological aging. Many questions remain unanswered. Nevertheless, even if physical activity does not directly cause telomere lengthening, and even if telomere length turns out to be a poor predictor of the pace of aging, physical activity is worthwhile because it reduces your risk of many chronic conditions, such as cardiovascular disease, type 2 diabetes, and hypertension.

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