id="ulink_aba54afc-5d70-5321-9f1c-f40982f4279e">Regarding the risk for developing T2DM, findings from the Uppsala Longitudinal Study of Adult Men (ULSAM) cohort indicated that after 20 years of follow‐up, those being overweight/obese but free of MetS had approximately 3.5 times increased risk of developing T2DM; the risk was eight times higher for overweight/obese individuals with MetS, relative to those of normal weight and free of MetS.
Contrary to the above findings suggesting that overweight/obesity is a risk factor for NCDs, other studies have shown that overweight and even grade 1 obesity (BMI = 30–35 kg/m2) are related to decreased all‐cause mortality by 6% and 5%, respectively, compared to those of normal BMI. Still, obesity grades 2 and 3 (BMI > 35 kg/m2) are associated with 18% and 29% increased risk of all‐cause mortality, respectively, compared to those of normal BMI.
There are many studies on BMI and mortality without uniform results. This is because many factors have been shown to confound the relationship between BMI and longevity. Possible residual confounding factors might be age, disease‐related weight loss, and individuals who smoked, had underlying diseases (e.g., cancer), or suffered early deaths.
In the elderly, mortality risk increases at BMIs lower than 22 kg/m2, which is not seen in younger adults, while a lower risk is observed among those with overweight and mild obesity. This paradoxical finding, i.e., lower mortality at higher than “healthy” BMI levels, has been termed “the obesity paradox.” There are many possible mechanisms to explain these findings. Excess fat may act as a metabolic reserve during illness or injury. In addition, because of lower noradrenaline‐stimulated lipolytic activity in visceral fat as age increases (which leads to insulin resistance and morbidity), individuals may be less affected by excess adiposity. Moreover, physicians often prescribe more medications to those with overweight and obesity, which may indirectly contribute to the obesity paradox.
Frequent changes from normal to obese and back (yo‐yo effect) have been linked to more than twofold increased risk of all‐cause mortality, relative to stable normal BMI. However, changes from normal weight to overweight (not obesity) were not linked to elevated all‐cause mortality risk, compared to stable normal weight. These findings were similar for CVD‐ and cancer‐specific mortality.
Tobacco Use
According to the WHO, tobacco use is responsible for more than six million deaths annually. Smoking is responsible for more than five million of those fatal events, whereas secondhand smoking results in more than 600,000 deaths annually. More than 4000 chemical substances are present in tobacco smoke; more than 250 of those have been linked to negative effects for human health. Furthermore, more than 50 chemical substances in tobacco smoke have been robustly associated with increased incidence of oropharynx, esophagus, stomach, liver, cervix, and colorectal cancer. Smoking is the leading risk factor of cancer‐specific deaths; it accounts for more than 20% of the global annual cancer‐induced mortality.
Key Point
Smoking is the leading risk factor of cancer-specific deaths; it accounts for more than 20% of the global annual cancer-induced mortality.
Tobacco use has been shown to have a causal relationship with the incidence of a variety of other chronic diseases, like stroke, CHD, T2DM, respiratory diseases, and impaired immune function. Smokers have 2–25 times higher risk for developing CHD and stroke when compared to nonsmokers. Smoking causes overall health deterioration, increases the number of days off from work, and increases health‐care utilization and cost. Quitting smoking can lead to important benefits in terms of longevity and mortality risk, especially for those who quit smoking early. Finally, it has been shown that heavy smokers live an unhealthier lifestyle compared to those who do not smoke, which usually includes sedentary lifestyle, excessive alcohol intake, and poor dietary habits.
Key Point
Quitting smoking can lead to important benefits in terms of longevity and mortality risk, especially for those who quit smoking early.
Excessive Alcohol Intake
Excessive alcohol intake has been recognized as a causal factor for more than 200 major types of diseases, injuries, and other health conditions – CVDs, T2DM, cancers, and gastrointestinal diseases, including liver cirrhosis and mental and behavioral disorders, as well as unintentional or intentional injuries. Figure 3.5 shows the distribution of alcohol‐attributable deaths in 2012, by broad disease category.
According to the US dietary guidelines issued in 2015, excessive alcohol consumption may include binge drinking (i.e., 4 or more drinks for women and 5 or more drinks for men within 2 hours) or heavy drinking (i.e., 8 or more drinks a week for women and 15 or more drinks a week for men) with an alcoholic drink‐equivalent defined as 14 g (0.6 fl oz) of pure alcohol. Examples of one alcoholic drink‐equivalent include 12 fluid ounces (~355 ml) of regular beer (5% alcohol), 5 fluid ounces (~148 ml) of wine (12% alcohol), or 1.5 fluid ounces (~45 ml) of 80 proof distilled spirits (40% alcohol).
Alcohol‐related health effects are associated with the volume of alcohol consumed and the pattern of drinking. For most alcohol‐related diseases, there is a dose–response relationship, which means that the higher the consumption of alcohol the higher the risk for disease development. The drinking pattern, reflecting the way people consume alcohol, may be equally important as to the amount consumed. Heavy episodic drinking or binge drinking, i.e., 60 or more grams of pure alcohol on at least one single occasion at least monthly, is an indicator of the pattern of alcohol consumption associated with detrimental health consequences.
Key Point
Alcohol-related health effects are associated with the volume of alcohol consumed and the pattern of drinking.
FIGURE 3.5 Distribution of alcohol‐attributable deaths, as a percentage of all alcohol‐attributable deaths by broad disease category, 2012.
Source: Reprinted with permission from WHO Library Cataloguing‐in‐Publication Data Global status report on alcohol and health – 2014 ed.
FIGURE 3.6 Patterns of drinking score (15+ years), 2010.
Source: Reprinted with permission from the WHO Library Cataloguing‐in‐Publication Data Global status report on alcohol and health – 2014 ed.
Countries with high per capita adult alcohol consumption, but with the least risky patterns of drinking, are in Southern and Western Europe, whereas the riskiest patterns of drinking are found in the Russian Federation, South Africa, Ukraine, Kazakhstan, and Mexico (Figure 3.6); half of all countries worldwide have a drinking pattern of intermediate risk.
Stress
People
