Cohort Profile: Indian Study of Healthy Ageing (ISHA-Barshi)

Le résumé fourni par la source

The Indian Study of Healthy Ageing (ISHA) examines the burden, causes and consequences of chronic diseases in an Indian adult population of ∼220 000. Once completed, ISHA will be the largest blood-based prospective study in South Asia. Expansion to sites in Varanasi, Guwahati, Sangrur and Mullanpur will further strengthen the study. Recruitment began in 2015 in Barshi, Maharashtra state, India. Enumeration, including basic baseline data collection, has been completed for all participants. Further detailed data collection, through questionnaires, physical measurements and blood sampling, is complete for ∼39 000 participants and ongoing. Active follow-up and linkage to health-related datasets (for death, cancer and hospitalization) provide data on fatal and non-fatal disease events. At baseline among the ∼39 000 participants, 53% were women, and mean (standard deviation: SD) age was 46 (11). Tobacco smoking and alcohol drinking are relatively uncommon, but tobacco chewing is prevalent (67% of men and 14% of women ever chewed tobacco). The population is relatively lean, with a mean (SD) body mass index of 23.2 (4.1) kg/m2. Self-reported, previously diagnosed chronic diseases were uncommon (hypertension: 6%; diabetes: 3%; cardiovascular disease: 1%; cancer: <1%). Depressive symptoms were common (at least one reported by 58%). Data-sharing regulations are in place; specific proposals for future collaboration are welcomed. The Indian Study of Healthy Ageing (ISHA) is a blood-based prospective cohort study of approximately 220 000 individuals aged 30–69, recruited between 2015 and 2020 from towns and villages around Barshi, Solapur district, Maharashtra state, India (Supplementary Figure S1, available as Supplementary data at IJE online). The study was established with the aim of testing hypotheses relating to lifestyle, diet, obesity and related factors, and of identifying potential genetic determinants of cancer and other chronic diseases in a general population with low baseline risk. Table 1 shows 2019 age-standardized mortality rates for middle-aged men and women in Barshi, India, the USA and the UK. All-cause mortality was notably higher in Barshi than in the USA and UK, but was moderately lower than India’s national mortality rates, particularly among women. Vascular disease accounted for about one-third of premature adult mortality in Barshi, and ischaemic heart disease accounted for a substantially higher proportion in Barshi than in the UK and USA. There were also notably higher respiratory disease mortality rates in Barshi, although rates were lower than in India overall among both men and women. Previous studies in India have reported similar patterns of vascular disease,1 but much remains unknown about factors underlying these recent trends in vascular mortality. ISHA would be expected to contribute significantly to advancing our understanding of environmental and genetic risk factors for vascular and non-vascular mortality in the Indian population. Major transitions in lifestyle behaviours have been seen in India and these continue, particularly in rural areas; a further aim of ISHA is to understand the relevance of these for common chronic diseases. Collection and long-term storage of blood samples will allow investigation of genetic susceptibility to cancer and other chronic diseases and of the relevance of other blood-based risk factors, which might conceivably differ from those in European ancestry populations. Age-standardized mortality ratesa at ages 30 to 69 for Indian Study of Healthy Ageing study areas in 2019 and, for comparison, India, USA and UKb Rates are age-standardized by taking the unweighted average of the component 5-year mortality rates (e.g. 30–34, 35–39, … 65–69 for the age range 30–69 years). Source: Global Burden of Disease Study 2019. IHD: Ischaemic heart disease. ISHA was conceived, developed and is coordinated by the Centre for Cancer Epidemiology (CCE), based at the Tata Memorial Centre, Kharghar, Navi Mumbai, India. Following an initial pilot study (funded by the International Agency for Research on Cancer, Lyon, France and the Centre for Global Health Research, Canada), the main study, including establishment of an automated biobank (for storing 3 million samples), is funded by Tata Memorial Centre. Participants were recruited from 362 villages and three small towns around Barshi (Warshi, Bhum, Paranda). Barshi was chosen given its relatively stable population, with little migration in and out of the region, and previous experience demonstrating the feasibility of long-term follow-up in the area. A Regional Coordinating Centre was established, led by medical and field coordinators (Supplementary Figure S2, available as Supplementary data at IJE online). Potentially eligible participants were identified through official residential records, and field coordinators visited their households. To encourage participation, all household members in the target age range (30–69 years) were eligible for enrolment into the study. Of 128 897 eligible households, 119 387 (93%) participated (Supplementary Table S1, available as Supplementary data at IJE online). Within participating households, 93% (n = 219 888) of eligible individuals were recruited to the study, with age and sex distributions similar to those of the 17 362 household members who were not recruited (Supplementary Table S2, available as Supplementary data at IJE online). After an enumeration process, fieldworkers visit participants’ homes to complete a detailed Household Health Survey interview. Since study villages do not have house numbers, unique enumeration numbers are marked on participants’ houses which, along with GPS records, ensure the correct houses are visited for completion of the Household Health Survey. At this time, letters are provided inviting participants to visit temporary Health Check-Up Camps set up inside the villages and towns, where physical measurements and blood samples are taken. As a pre-requisite for participating, all participants are asked to show their unique national identity (ID) cards—Aadhaar cards2—to fieldworkers when they visit their homes. Of the 38 442 participants who have completed the Household Health Survey to-date, 30 398 (79%) have attended the Health Check-Up Camp, with no significant differences in sociodemographic and lifestyle characteristics of participants according to attendance. All participants provided informed consent, which allows access to participants’ medical records and long-term storage of blood for anonymized and unspecified medical research purposes. Periodic resurveys of reasonably representative samples of ∼10 000 participants will be performed every 5–10 years (Supplementary Figure S3, available as Supplementary data at IJE online). These will be important for assessing temporal trends, e.g. in lifestyle and sociodemographic factors, given the ongoing rapid development in rural India, as well as providing opportunity for further enhancement of data collection. Moreover, these resurveys will enable assessment of within-person variation in exposures, and correction for resulting ‘regression dilution’ bias.3 Vital status of participants is being monitored indefinitely based on manual linkage to death registries and through active follow-up (Supplementary Figure S4, available as Supplementary data at IJE online). Verbal autopsies are conducted by study staff to determine the most likely cause of death.4,5 Further manual linkage to cancer registries,6,7 primary health care and hospital registers (employed in these established cancer registries), and the Rajeev Gandhi Health Insurance Scheme,8 in addition to active follow-up, provide data on disease incidence (Supplementary Figure S5, available as Supplementary data at IJE online). Additional active follow-up is undertaken approximately every 3–5 years through fieldworker visits to participants’ households (Supplementary Figure S6, available as Supple

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