Category: Specialists-Cardiology

FROM 1960 till 2020, there has been a 28-fold increase in the number of centenarians. The path to longevity is strewn with false promises of expensive elixirs, exotic supplements, and stem cell rejuvenation. Human longevity is a complex interplay between the genes, the environment and lifestyle.

Genes and longevity
The study of human longevity genes is a developing science. Scientists estimate that between 15 and 30 per cent of the variation in human life span is determined by genes, but it is not clearly understood which genes are relevant, and how they contribute to longevity. In 2015, Ancestry, a genealogy and genetics company, partnered Calico, a Google spinoff, to study data from more than 54 million families and their family trees representing six billion ancestors, and were able to tease out a set of pedigrees that included over 400 million people. These individuals were connected to one another by either a parent-child or a spouse-spouse relationship.

In 2018, they published their results in Genetics, a journal of the Genetics Society of America. The study found that the lifespan of spouses were more similar and better correlated than in siblings of opposite gender. The study concluded that life span heritability is likely 7 per cent or less, and hence the contribution of genes to longevity is even lower.

Although genes seem to have only a small influence on lifespan, they appear to play a larger role in centenarians. Hence, there are a few genetic
factors that do give you a headstart in the journey to longevity. Being a first-degree relative of a centenarian makes it more likely for you to remain healthy longer and to live to an older age than your peers. First-degree relatives are less likely at age 70 years to have the age-related diseases that are common among older adults.

Women generally live longer than men, and the number of female centenarians is more than fourfold higher than that of male centenarians. It is
thought that this is due to a combination of social and biological factors. Studies on mammals and Korean eunuchs have shown that the removal of
testosterone at a young age was correlated with an increase in lifespan. Genetic studies show that centenarians have a lower genetic risk of having
heart disease, stroke, high blood pressure, high cholesterol, Alzheimer’s disease and decreased bone mineral density.

A study on Chinese centenarians published in 2013 showed that 55 per cent have normal systolic blood pressure, 82 per cent had normal diastolic blood pressure and less than 20 per cent were on long term medication. Hence, centenarians appear to have genes that reduce that risk of age-related chronic illnesses.

Biological clock
Epigenetics is the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself. One of the major mechanisms in which epigenetics manifest itself is by the process of DNA methylation, which involves the chemical modification of the DNA, thereby modifying the gene function and expression. Through this process, certain genes can be silenced or activated and potentially impact age-related diseases such as cancer, osteoarthritis, and neurodegeneration.

The biological or epigenetic lock in centenarians show a decrease in DNA methylation age, indicating that they are biologically younger than their chronological age. There is also data to suggest that although circadian rhythms deteriorate during ageing, they seem to be well preserved in centenarians, including preserved sleep quality.

Environment and longevity
Environmental factors have a large impact on longevity. Better living environment, clean food, clean water, good sanitation, reduction of infectious diseases, and access to better healthcare have resulted in significant improvement in human longevity. Using Italy as an example of the impact of a better living environment, the average life expectancy went up from 29 years in 1861 to 84 years in 2020.

The number of centenarians in Italy increased from 165 in 1951 to more than 15,000 in 2011, and the incidence of deaths occurring in those less than 60 years of age, decreased from 74 per cent in 1872 to less than 10 per cent in 2011. The continuous increase in lifespan in recent decades is mainly due to the advances in medical science. It is estimated that medical advances have allowed an increase in lifespan of five years in the last two decades and additional two years in the last decade.

When comparing two countries at different stages of development in 1950, the average life expectancy increase of 11 years from 68 years in 1950 to 79 years in 2020 in the USA, which was more developed in 1950, was much less remarkable than the increase of 3114 years in average life expectancy from 43 years in 1950 to 77  years in 2020 in China, which was less developed in 1950. The significant improvement in the living environment in China has contributed to the narrowing in the average life expectancy between those living in the US and China.

Lifestyle and longevity
In addition to environmental factors, lifestyle factors have an important impact on longevity. A study of more than 300,000 individuals over 7.5 years showed that individuals with social relationships have more than 50 per cent greater probability of survival compared with those with few and poor social interactions. A study on centenarians in Utah in the US between 2008 and 2015 suggested that sleep, life satisfaction and social attachment were significant predictors of days lived. There is an extricable linkage between lifestyle and socioeconomic status. The term  socioeconomic status as used in longevity studies encompass all the factors that can impact longevity including wealth, geography, education, occupation, ethnicity, cultural environment, neighbourhood environment, quality of healthcare and quality of diet. It is well established that the socioeconomic status of an individual will have a major impact on health and longevity.

A study on more than 120, 000 individuals by researchers from Harvard, published in the Circulation journal in April 2018, identified five low-risk lifestyle factors for increased life expectancy. They were: no smoking, non-obese ( body mass index of 18.5 to 24.9 kg/m2), exercise (at least 30 minutes per day of moderate to vigorous physical activity, including brisk walking), low-risk alcohol consumption (5 to 15 gm/day for women and 5 to 30 gm/day for men), and a high score for healthy diet.

In this study, the projected life expectancy at age 50 years was on average 14.0 years longer among female Americans with five low-risk factors
compared with those with zero low risk factors; for men, the difference was 12.2 years. These findings are consistent with a study on Chinese centenarians in which less than 20 per cent were smokers and less than 40 per cent drank alcohol. Hence, in general, most centenarians do not smoke, do not drink alcohol or are low-risk alcohol drinkers, are sociable, friendly, cope well with stress, are satisfied with life, have healthy diets and sleep well. In summary, the main drivers of longevity in the first eight decades of life are the socioeconomic environment and lifestyle choices.

Beyond the eighties, the inheritance of genes that defer age-related chronic diseases and a younger biological clock will help to propel these individuals beyond a hundred years.

BLOOD pressure (BP) continues to be an important determinant of our health and has significant implications for many diseases including stroke, heart disease, kidney damage and eye disease. Understanding how our lifestyles impact our blood pressure can help us make the right decisions in maintaining a healthy range of BP.

Normal BP fluctuation
There is a diurnal physiological variation in BP, which rises on wakening in the early morning when the person gets up, reaches a plateau during the morning, decreases slightly in the early afternoon and rises again in the early evening. The BP then decreases gradually in the late evening, drops sharply after falling asleep and is lowest during sleep at about 3am. The BP increases again by about 20 per cent between 6am and 8am, around the time of awakening. If the sleep-time relative systolic blood pressure (SBP) decline is 10 per cent or more, this sleep pattern is considered a normal dipper pattern. In the majority of normotensive persons, the decrease in BP from daytime to night time is about 10 per cent to 20 per cent.

While many may think that this is due to your internal body clock, in truth, the variation associated with the sleep wake cycle is largely influenced by mental and physical factors. Hence, in shift workers, BP is high during work at night and low during sleep in the day.

Morning BP surge
The typical physiological morning elevation in BP is more a function of activity rather a function of the time of the day. Those who remain supine in bed after waking up do not show much change in their BP, which rises rapidly only when the person gets upright. The extent of BP elevation is related to the level of physical activity. In some patients with hypertension, an exaggerated increase in BP is seen and this is termed the morning surge.

Upon awakening and getting up and commencing activities of daily living, there is a large surge in your “fight or flight” hormones, namely the catecholamines (such as adrenaline). This results in increase in heart rate, increase in BP, greater pumping action of the heart, increase in your arterial vessel tone and decrease in the calibre of the arteries.

Other awakening changes include an increase in your body steroids (cortisol) level, and “thickening” of the blood (due to increased tendency of the platelets to stick together and an increase in blood viscosity). These changes result in an increased demand for oxygen by the heart, decrease in oxygen supply to the heart and “thickening” of the blood. These changes may help to explain the increase in heart and stroke events during the morning. Analysis of combined trial data has demonstrated an approximately 40 per cent increase in incidence of heart attacks, close to 30 per cent increase in incidence of heart-related deaths and close to 50 per cent increase in incidence of stroke, as compared to other periods of the day. In addition to the morning surge, hypertensive patients tend to have no dip in BP (non-dipping) at night. The nighttime non-dipping is associated with damage to key organs (such as the heart, brain and kidney) and heart disease.

Stress and BP
As everyone knows, stress increases BP. The stress of doing housework or rushing to work in the morning may cause an exaggerated surge in morning BP and even morning hypertension. Workplace stress can also cause daytime hypertension. A study reported that more than 20 per cent of civil servants who had workplace hypertension had normal BP during health examination. Interrupted sleep results in elevated BP and may contribute to the non-dipping of BP at night. It has been shown that hospitalisation can reduce stress, resulting in lower BP in the day and reduced difference between daytime and night-time BP in hypertensives. Activities such as meditation can also lower BP effectively.

Lifestyle and BP
There is little surprise that obese individuals have higher BP values than normal individuals. The good news is that weight loss in hypertensives can result in reduction in BP. Many obese individuals have obstruction of their upper airway resulting in snoring and a condition called obstructive sleep apnoea. This decrease in oxygen delivery to the body as a result of airway obstruction during sleep is associated with an increase in nighttime BP.

During exercise, BP increases and post-exercise, it decreases. This post exercise drop is due to a relaxation of the tone of the blood vessels and usually lasts for several hours. Several studies have also shown that regular exercise lowers BP in both normotensives and hypertensives. The impact of exercise on BP is  dependent on the time of exercise, with morning exercise resulting in decrease in daytime BP and evening exercise decreasing night-time BP in non-dippers (hypertensive pattern), but not dippers (normal pattern).

Taking a hot shower usually causes a rise in BP initially, but if you are immersed in a hot bath, BP will decrease with even further decrease immediately after the bath. It will gradually return to the baseline levels after about one hour. For smokers, studies using ambulatory BP monitoring have shown that only daytime BP is elevated, and it is higher on smoking than on nonsmoking days. Therefore, chronic smoking can cause daytime hypertension.

Food and BP
It has been observed that there is a mild increase in BP during meals as a result of increased physical activity, followed by a fall after meals as a result of dilatation of the vessels in the gut in response to food consumption. This post-prandial drop in BP is minor in the young but may be more pronounced in the elderly, in hypertensives, and following a high-carbohydrate meal (as compared to high-fat meal).

The peak of the post-prandial reduction in BP is at about one hour and persists for more than two hours. It is a well-known fact that a high sodium intake increases BP and a low sodium intake can decrease it. In contrast, dietary intake of potassium and magnesium is inversely related to BP. Hence, the consumption of fruits and vegetables that are rich in potassium and magnesium may decrease BP in hypertensives. Coffee lovers may be surprised to know that consumption of coffee can transiently increase the BP by up to 10 mm Hg for about one hour. Much of this is believed to be due to the effects of caffeine on the body. Conversely, the consumption of cocoa or dark chocolate appears to be associated with a significant reduction in 24 hours’ BP.

Conclusion
Shedding excess weight by exercising, followed by a hot bath immersion, consumption of dark chocolate, fruits and vegetables (high in magnesium and potassium) and ending the day with stress-relieving meditation is a perfect recipe for lowering the blood pressure. In addition, reducing salt, coffee, excessive weight, smoking and stress will certainly help you achieve the ideal BP and ultimately a healthy life.