By Kerry Grens
NEW YORK (Reuters Health) - A study of Indians who migrated from rural to urban areas finds that the longer they live in a city, the worse they score on measures of heart health and diabetes risk, compared to those who remained in rural areas.
Body fat, blood pressure and fasting insulin levels (a marker of diabetes risk) all increased within a decade of moving to a city, and for decades blood pressure and insulin continued to rise above the levels of their rural counterparts. The findings raise public health concerns as the global population progressively becomes more urban.
According to the United Nations, the growth change in India's urban population is 1.1 percent each year, while the change in the proportion of people in rural areas is declining by 0.37 percent.
The proportion of Indians who live in cities is still much smaller than in the United States. Just 30 percent of Indians live in urban areas, while 82 percent of Americans live in urban areas.
That number is expected to rise as the proportion of people who live in rural areas in the United States declines by 1.6 percent each year.
The researchers, led by Dr. Sanjay Kinra of the London School of Hygiene and Tropical Medicine, compared rural Indians to their siblings who moved to one of four cities in India: Lucknow, Nagpur, Hyderabad and Bangalore. Siblings who lived in a city the longest had the highest average blood pressures.
For instance, men who lived in a city for more than 30 years had an average systolic blood pressure - the top number in a reading -- of 126. Men who lived in a city 10-20 years had an average of 124, and those who stayed in rural areas had an average of 123. A systolic blood pressure above 140 is considered high.
The change in body fat was most evident in the first 10 years after moving to a city, and then it leveled off. Men who stayed in rural areas had 21 percent body fat on average, while those who moved within the past ten years had 24 percent, on average. The recommended body fat percentage from the National Institutes of Health is 13 to 17 percent.
The study, published in the American Journal of Epidemiology, did not pinpoint the cause of these differences between the siblings who moved and those who stayed behind. Nor did it tease out whether the increased levels of body fat, blood pressure and insulin resulted in more disease.
Though other studies of rural-to-urban migration within developing countries have also found negative health effects related to moving to cities, city dwellers in the United States tend to be healthier than those who live rural areas and even in the suburbs.
According to the Agency for Healthcare Research and Quality, Americans who live in rural areas are more likely to have fair or poor health, develop chronic diseases, and die from heart disease.
One study of suburbanites across several countries found that people who lived in cities were more likely to be active and to walk places. People in cities also tend to be closer to doctors and hospitals.
The authors write that the changes among the Indian city-dwellers might be explained by rapid weight gain once people move to a city, spurred by a less healthy diet and a less active lifestyle.
"Programs focused on preventing obesity in new migrants to urban areas and tailored to the needs of those in lower socioeconomic positions could deliver long-term health benefits," the authors wrote.
SOURCE: American Journal of Epidemiology, online May 27, 2011.