One third of the inhabitants of the city of São Paulo or, more precisely, 32.9%, live with a chronic breathing problem that impairs sleep and worsens the quality of life. It is called the syndrome of obstructive sleep apnea, a series of brief suspensions of breathing that generally cause one to awaken briefly. As people who suffer from apnea may wake up without realizing it whenever they becomes short of air, experiencing at least five breathing pauses of as many as ten seconds per hour, they do not rest as they should. The consequences of this materialize on the following day: sleepiness, napping at the wrong time, irritability and impaired productivity. If untreated, apnea increases the risk of cardiovascular problems.
Discovering that one out of every three people in the city of São Paulo suffers from apnea and that many are unaware of it is one of the most amazing results of the broadest and most detailed survey ever conducted about the quality of sleep for the inhabitants of the city of São Paulo. The proportion of cases identified in this study is so high that it even bothered the coordinators of the study, which was conducted by a team from the Federal University of São Paulo (Unifesp). They had expected to find a rate of apnea only slightly higher than that which had been observed in previous studies in Brazil and abroad, which indicated prevalence from 2 percent to 7 percent among adults, but nowhere near what they found in São Paulo.
Other results of this study, which evaluated the quality of sleep of 1,101 people chosen randomly from the state capital’s 11 million inhabitants, are closer to those of other studies. And they also show that sleeping poorly may by the fate of those who live in São Paulo: 25% of the city’s inhabitants have difficulty falling asleep; 42% snore, often due to apnea; 24% have nightmares at least once a month; and 13.2% suffer from chronic insomnia.
Women are less prone to apnea and to snoring than men – the ratio of apnea cases evolves differently in the two groups, rising gradually as men age, but increasingly suddenly among women after menopause. However, they say that they find it harder to fall asleep. Nightmares affect the sleep of 30 % of the women, but of only 17 % of the men. The percentage of women with chronic insomnia (16.5%) is about twice as great as that of men (9.2%) and daytime sleepiness is also more common among women (10% of them feel sleepy during the day, vs. 7% of the men).
There are reasons to believe that these data represent the reality of the population of the city of São Paulo and of other metropolises better than those that were previously known. “As a result of material or financial limitations, the preceding studies were conducted with samples that did not represent the entire set of the population, such as factory workers, nor did they include the low-income population or people who tend toward obesity”, explains Rogério Santos Silva, the study’s coordinator.
The stamina and motivation for a broader study were provided by the physician Sergio Tufik, the director of the Sleep Institute of Unifesp and of the Sleep Cepid (Center for Research, Innovation and Dissemination, financed by FAPESP). Besides taking part in the planning, and adding to it his three decades of experience in the field, Tufik released 16 of the institute’s 80 beds and R$2.4 million of the Cepid funding for this survey.
The Unifesp researchers hired a statistician and interviewers from specialized firms to analyze the IBGE population maps and to select the potential interviewees in each city district: people aged 20 to 80 who represented the age, gender and social class distribution of the São Paulo state capital.
To avoid skewed results – the seasons of the year, for instance, tend to increase or diminish the number of hours of sleep – the research was conducted over six months, from July to the end of December 2007. Out of the 1,101 people selected who accepted taking part in the study and who answered questionnaires on their patterns of sleep and its quality, 1,042 were taken to sleep for one night at the Sleep Institute, where they took a polysomnograph test, which records the brain’s electrical activity, body movements, heartbeats, and breathing during sleep, and did blood tests, to evaluate their general health. Silva and Roberta Siufi accompanied the almost 60 people who interviewed, transported and examined the study’s participants. “On many nights, we took up all of the 16 beds made available for this study at the institute”, Silva tells us. With this information, the Unifesp group built a database with some 900 variables that should still tell us a lot more about the metropolis and its 10 million inhabitants.
The high rate of apnea can perhaps be explained not only by the survey’s breadth and methodological care, but by the prevalence, also higher than expected, of one of its causes: weighing more than what health authorities consider healthy. “I was expecting something around the national average of 30%, but not 60% overweight or obese people”, says José Augusto Taddei, one of the Unifesp researchers that led this study. “Because of the higher food purchasing capacity and more sedentary lifestyle, São Paulo is different from Brazil.” In Geografia da Fome [The Geography of Hunger], a pioneering study on nutrition in Brazil, published in 1946, physician Josué de Castro observed that the inhabitants of the Southeast, the country’s economically richest area, ate more than those from the country’s other regions. More, but not necessarily better.
This Unifesp survey shows that the weight of only 40% of the men is within the desirable range; 36% are overweight, 17.2% are obese; and 6.65% are morbidly obese. Among the women, 37% have normal weight, 34% are overweight, 20.3% are obese and 8.65% are morbidly obese.
The researchers’ analysis established a direct relation between apnea and excess weight: the risk of developing a breathing problem is 2.6 higher among overweight people and 10.5 greater among the obese versus those whose weight is normal. “Nobody dies from apnea”, comments Silva, “but from its consequences, which increase the risk of heart attacks, strokes, hypertension, and involvement in car and occupational accidents, as a result of daytime sleepiness.”
Miguel BoyayanTwenty years of sleep
Apnea, which in this study appeared to be more common among lower income, older people, in line with other surveys, is one of the sleep disorders that are hardest to treat. Those who suffer from it and want to breathe better at night need to lose weight if they are carrying extra kilograms and use a device known as CPAP, a silicon mask connected to a small compressor that makes it easier for air to pass through the larynx. One of the factors that limits access to CPAPs is the price, which ranges from R$500 to R$1,000. “One alternative is a type of surgery performed by otorhinolaryngologists, which the public health service subsidizes, but that is not the best treatment”, notes Silva.
Sleeping badly and finding oneself sleepy, irritable, tired, with a short attention span and a short memory the following day has become more of a problem over the last 20 years in the city of São Paulo, as the researchers discovered by comparing data from the current survey with information from two other studies carried out in the past by the same Unifesp group. The two previous studies, one from 1987 and the other from 1995, evaluated (though only through questionnaires, the same ones used in the present survey) the quality of sleep of about 1,000 individuals. The stories about having difficulty sleeping for more than three nights a week practically doubled, from 13.9% in 1987 to 25% in 2007. The frequency of stories about daytime sleepiness more than doubled (2.8% in 1987 and 8.6% in 2007), while the frequency of nightmares more than once a month rose from 11% to 24%. The Unifesp researchers did not evaluate this, but they know – and they witness it every day – that the city has become more hostile, with more traffic, noise and violence. “When the quality of life deteriorates”, says Taddei, “the quality of sleep drops.”
Because of its breadth, Taddei believes that this study might change the perception of sleep disturbances in metropolises worldwide. “There is no reason for us to think that the results, when evaluated with the same methodological strictness, should be very different in New York or Bangladesh.” However, it is still impossible to make such comparisons because the studies conducted in large cities are not very broad, whereas those that are broad are conducted in smaller cities. One of the broadest surveys evaluated the quality of sleep of the inhabitants of Dauphin and of Lebanon, two towns in southern Pennsylvania, in the United States, which now have almost 300 thousand and 30 thousand inhabitants. Edward Bixler and other researchers from Pennsylvania State University interviewed, by phone, 12,219 women and 4,364 men aged 20 to 100 in these two towns. After, they evaluated the quality of sleep, using polysomnographs, among 1,000 women and 741 men among the interviewees. They detected apnea among 3.9% of the men and 1.2% of the women.
The Unifesp team now faces to battles. One is publishing their results, which are very different from those of other studies. The first two journals to which they submitted the study refused it, saying that the prevalence of apnea was too high. “One of the editors suggested that we conduct the study again,” tells us Silva. Taddei considers: “There is serious prejudice against data that comes out of Brazil, especially in a study such as this one, which has no co-authors from the United States.” A third journal is yet to inform whether or not it will accept the São Paulo apnea study.
The second battle is to teach people how to sleep better and lose weight. This implies in changing habits that impair sleep, such as eating a lot, working in bed or drinking alcoholic beverages before bedtime. “People who drink before going to bed are going to snore more and miss the deeper part of sleep”, states Silva. In the book Counting Sheep – The science and pleasure of sleep and dreams, Paul Martin, an English biologist, offers some other suggestions, such as guilt-free napping, regarding one’s bed as the most important piece of furniture in the household, and having a cozy bedroom, rather turning it into a junk depot.
For two decades, Taddei has focused on motivating people to eat better and to lose weight. “The fact that two out of every three people are overweight means that we are already at the peak of the obesity curve, as in the United States”, he warns us. “We must start to turn this around.” In the pursuit of new possibilities for action, with Unifesp’s support, he created a web page (Estilo de Vida Saudável [Healthy Lifestyle]) with recommendations on losing weight and experiencing better days and nights – and not only in the large cities.Republish